ACTA CARSOLOGICA KRASOSLOVNI ZBORNIK XXVI/1 (1997) UDC 556.3(497.4-14) ISSN 0583-6050 © 1997 Znanstvenoraziskovalni center SAZU SLOVENSKA AKADEMIJA ZNANOSTI IN UMETNOSTI ACADEMIA SCIENTIARUM ET ARTIUM SLOVENICA RAZRED ZA NARAVOSLOVNE VEDE CLASSIS IV: HISTORIA NATURALIS ZNANSTVENORAZISKOVALNI CENTER SAZU INŠTITUT ZA RAZISKOVANJE KRASA - INSTITUTUM CARSOLOGICUM ACTA CARSOLOGICA KRASOSLOVNI ZBORNIK XXVI/1 1997 iS - Si -t.-// 1947 - 1997 JCARST HYDROGEOLOGICAL INVESTIGATIONS IN SOUTH-WESTERN SLOVENIA LJUBUANA 1997 Uredniški odbor - Editorial Board Acta carsologica: Franco Cucchi, Jože Čar, Ivan Gams, Andrej Kranjc Marcel Lalkovič, Mario Pleničar, Trevor R. Shaw, Tadej Slabe 7. SWT: Janja Kogovšek, Metka Petrič, Dieter Rank, Barbara Reichert, Janko Urbane Glavni in odgovorni urednik - Editor Andrej Kranjc The authors are fully responsible for the content and for the language of their contributions. Zamenjava - Exchange Biblioteka SAZU Novi trg 5/1, SI - 1000 Ljubljana, p.p. 323, Slovenija Naslov uredništva - Editor's address Inštitut za raziskovanje krasa ZRC SAZU SI - 6230 Postojna, Titov trg 2, Slovenija Tiskano s finančno pomočjo Ministrstva za znanost in tehnologijo RS, Ministrstva za okolje in prostor RS in generalnega sponzorja 7. SWT - HIT Hoteli Igralnice Turizem Published by the financial assistance of Ministry of Science and Technology RS, Ministry of Environment and Physical Planning RS, and HIT Hotels Casinos Tourism, General Sponsor Po mnenju Ministrstva za znanost in tehnologijo RS št. 415-01-137/94, z dne 26. 4. 1994, je publikacija uvrščena med proizvode, za katere se plačuje 5-odstotni davek od prometa proizvodov. CONTENTS 1. PREFACE (A. Kranjc).........................................................................................11 2. NATURAL BACKGROUND..............................................................................15 2.1. Physical Geography of Trnovsko-Banjška Planota (P. Habič)...................15 2.2. Hydrology (N. Trišič).........................................................................................19 2.2.1. Basic description of the area........................................................................19 2.2.2. The springs of the Vipava............................................................................20 2.2.3. The area of the Trnovsko-Banjška Planota...............................................23 2.3. The climate of the Trnovsko-Banjška Planota (J. Pristov).......................30 2.3.1. Meteorological conditions...............................................................................30 2.3.2. The water balance...........................................................................................33 2.4. Geomorphologie Review of Trnovsko-Banjška Planota (P. Habič)..........38 2.4.1. General orographic-hypsographic properties..............................................38 2.4.2. Geomorphology of single orographic units................................................42 2.4.2.1. Banjšice between the middle Soča valley and dry Čepovan valley .... 42 2.4.2.2. Trnovski Gozd, Križna Gora, Javornik, Zadlog and Črni Vrh.........46 2.4.2.3. Črnovrška Planota, Zadlog, Idrijski Log, Predgriže and Lome.........51 2.4.2.4. Nanos with Hrušica and Zagora and the northern border of the Pivka basin........................................................................................52 2.4.3. Geomorphological Processes and Development........................................55 2.5. Speleological properties of the area (A. Mihevc) ......................................57 2.6. Geology and Hydrogeology...............................................................................68 2.6.1. Geological Description (L Čar)....................................................................68 2.6.1.1. Lithostratigraphic Description.....................................................................70 2.6.1.2. Tectonics..........................................................................................................72 2.6.2. Hydrogeology (J. Janež).................................................................................73 2.6.2.1. The review of the previous investigation................................................73 2.6.2.2. Hydrogeological Classification....................................................................74 2.6.2.3. Karst Aquifer of Nanos and Hrušica......................................................76 2.6.2.4. Hydrogeologie Structure of Trnovski Gozd and Banjšice Plateau .... 76 2.6.2.5. Important Springs.........................................................................................77 2.6.3. Geological structure and hydrogeological position of the Hubelj spring (J. Janež)................................................................................82 2.6.3.1. Extent and method of mapping................................................................82 2.6.3.2. Geological structure near the Hubelj spring..........................................84 2.6.3.3. Hydrogeological position of the Hubelj spring......................................86 2.6.4. Geologic conditions and some hydrogeologic characteristics of the Vipava karst springs (J. Janež, J. Čar).....................................................86 2.6.4.1. The aim and method of investigation.....................................................86 2.6.4.2. The review of previous investigation.....................................................88 2.6.4.3. Geology and morphology at the Vipava springs and their hydrogeologic consequences........................................................................88 2.6.4.4. Some hydrologic data..................................................................................91 2.7. Water Quality.......................................................................................................92 2.7.1. Long-term Quality Monitoring (M. Zupan)..............................................92 2.7.1.1. Introduction....................................................................................................92 2.7.1.2. Sampling And Chemical Analyses Program...........................................92 2.7.1.3. Analytical Methods And Water Quality Standards...............................93 2.7.1.4. Results and water quality assessment......................................................98 2.7.1.5. Contour diagrams of fluorescence intensity.........................................102 2.7.1.6. Conclusions...................................................................................................102 2.7.2. Agricultural threats to pollution of water of Trnovsko-Banjska Planota (B. Matičič)....................................................102 2.7.2.1. Introduction..................................................................................................102 2.7.2.2. Groundwater and surface waters.............................................................104 2.7.2.3. Nitrogen balance at regional and farm level.......................................106 2.7.2.4. Nitrogen surpluses as possible source of water pollution.................107 2.7.2.5. National nitrate policies............................................................................112 2.7.2.6. Conclusions...................................................................................................113 2.8. Fauna in selected karst springs from the Trnovsko-Banjska Planota (A. Brancelj).....................................................114 2.8.1. Introduction.....................................................................................................114 2.8.2. Results..............................................................................................................115 2.8.3. Discussion........................................................................................................116 2.9. Phytogeographic Characteristics of the Trnovski Gozd (T. Pipan)........117 3. INVESTIGATIONS OF THE WATER BALANCE (1993-1995)............123 3.1. Hydrological Investigations in the Area of the Trnovsko-Banjska Planota Plateau between 1993 and 1995 (N. Trišic)...............................123 3.2. The Water Balance of the Trnovsko-Banjska Planota (J. Polajnar, J. Pristov, M. Bat, M. Kolbezen)........................................135 3.2.1. Introduction.....................................................................................................135 3.2.2. The method of establishing water balance for the area of the TBP without separation..................................................................136 3.2.3. The method of establishing water balance for the area of the TBP with the underground drainage..........................................138 3.2.4. Conclusions......................................................................................................141 3.3. Precipitation Problems in Relation to Water Runoff on the Trnovski Gozd (J. Pristov).............................................................................142 3.4. Correlation and Spectral Analysis (Ph. Martin, J. Kogovšek, M. Petrič, S. Šebela, C. Martin)................144 3.4.1. Methodology....................................................................................................144 3.4.2. Characteristics of the Used Data...............................................................146 3.4.3. Analysis of Results and Comparative Study of Both Springs............148 3.4.4. Separate Analysis of the Cycles 1993-1994 and 1994-1995.................154 3.4.5. Conclusions......................................................................................................155 3.5. Hydrological Description of the Vipava and Hubelj spring systems (S. Schumann, C. Leibundgut)..........................................157 3.5.1. Discharge Frequency Density......................................................................157 3.5.2. The Recession Curve Analysis....................................................................163 3.6. The Electrical Conductivity as Indicator for Hydrodynamic Processes in the Vipava System (T. Harum, H. Stadler, N. Trišič).... 168 3.6.1. Measuring Equipment...................................................................................168 3.6.2. Suppositions and Methodological Aspects................................................169 3.6.3. Separation of the discharge components..................................................171 3.6.3.1. Analysis of long-term fluctuations of the runoff year 1995.............171 3.6.3.2. Analysis of single events...........................................................................175 3.6.4. Reservoir water volumes and aquifer characteristics.............................179 4. HYDROCHEMICAL INVESTIGATIONS....................................................182 4.1. Long-term observations (M. Zupan)............................................................182 4.1.1. Monthly observations of water of the karst springs and selected rivers (J. Kogovšek)......................................................................182 4.1.1.1. Temperature..................................................................................................183 4.1.1.2. Calcium, magnesium and total hardness...............................................184 4.1.1.3. Chloride, nitrate, sulfate, sodium and potassium................................187 4.1.2. Monthly observations of the precipitation (M. Zupan)........................188 4.1.3. Weekly samphng in the springs Hubelj and Vipava (M. Zupan).....188 4.1.4. Comparative measurements of the Vipava springs (J. Kogovšek).....196 4.2. Observation of single events..........................................................................199 4.2.1. Daily samphng in the springs Hubelj, Vipava and Mrzlek (M. Zupan).....................................................................................................199 4.2.2. Water pulse of the Vipava spring - Pod Lipo 4/2 (J. Kogovšek).................................................................................................203 4.2.3. The Use of Silica to characterise the allogenic Flysch Component in Vipava Springs during the observation of Single Events (V. Armbruster, C. Leibundgut)......................................206 4.2.3.1. Introduction..................................................................................................206 4.2.3.2. Methods.........................................................................................................207 4.2.3.3. Results...........................................................................................................207 4.2.3.4. Conclusions...................................................................................................211 5. ISOTOPIC INVESTIGATIONS........................................................................213 5.1. Environmental Isotope Investigations (W. Stichler, P. Trimborn, P Maloszewski, D. Rank, W. Papesch, B. Reichert)...............................213 5.1.1. Introduction.....................................................................................................213 5.1.2. Precipitation.....................................................................................................215 5.1.2.1. Seasonal variation.......................................................................................215 5.1.2.2. Short term variation...................................................................................218 5.1.3. Altitude Effect................................................................................................220 5.1.4. Long-term observation..................................................................................221 5.1.4.1. Altitude of the catchment........................................................................221 5.1.4.2. Mean residence time..................................................................................225 5.1.5. Short term observation.................................................................................227 5.1.5.1. Vipava spring...............................................................................................228 5.1.5.2. Hubelj spring...............................................................................................231 5.1.5.3. Additional karst springs.............................................................................233 5.1.5.4. Results...........................................................................................................235 5.2. Dissolved Inorganic Carbon Isotope Composition of Waters (J. Urbane, B. Trcek, J. Pezdic, S. Lojen)................................................236 5.2.1. Carbon Isotope Composition In Individual Parts Of The Researched System........................................................................................237 5.2.1.1. Characteristics of carbon isotope composition of soil CO^..............237 5.2.1.2 Carbon isotope composition of carbonate rocks..................................242 5.2.1.3. Isotope composition of the total dissolved inorganic carbon in the outflow...............................................................................242 5.2.2. Reconstruction of Initial CO^ Isotope Composition..............................251 a) The Open System Model..................................................................................251 b) The Closed System Model................................................................................251 5.3. Short-term Investigations during a heavy Snowmelt Event (V. Armbruster, C. Leibundgut)...................................................................256 5.3.1. Introduction.....................................................................................................256 5.3.2. Methods............................................................................................................256 5.3.3. Results and Interpretation...........................................................................256 5.3.4. Conclusions......................................................................................................259 6. TRACING EXPERIMENTS.............................................................................260 6.1. Organisation, Injection and Sampling (A. Kranjc, J. Kogovšek, R. Benischke, B. Reichert, M. Zupan, M. Heinz-Arvand)...................260 6.1.1. First Combined Tracing experiment in October 1993 ..........................263 6.1.2. Second Combined Tracing experiment in April 1994...........................265 6.1.3. Third Combined Tracing Experiment, August 1995 ..............................268 6.1.4. Fourth Combined Tracing experiment, October 1995 ...........................273 6.2. Description of the Hydrological Situations during the Tracing Experiments (N. Trišič & J. Polajnar)........................................................274 6.2.1. The Hubelj Spring in the Time of the First Tracing Experiment (October 14 to December 31, 1993)...................274 6.2.2. The Hubelj Spring in the Time of the Second Tracing Experiment (April 16 to July 31, 1994)...................................276 6.2.3. The Hubelj Spring in the Time of the Third Tracing Experiment (August 1 to December 31, 1995).......................277 6.2.4. The Vipava Spring in the Time of the Fourth Tracing Experiment (October 26 to December 31, 1995)...................278 6.3. Results with Fluorescent Tracers...................................................................280 6.3.1. Analytical Procedures (R. Benischke, B. Reichert, M. Zupan)..........280 6.3.2. Results of the Hubelj - Mrzlek- Podroteja Area (M. Zupan, B. Reichert).............................................................................283 6.3.2.1. First Tracing Experiment in October 1993...........................................283 6.3.2.2. The Second Tracing Experiment in April 1994 ..................................285 6.3.2.3. Third Tracing Experiment in August 1995...........................................288 6.3.2.4. Summary.......................................................................................................292 6.3.3. Results of the Vipava Area........................................................................295 6.3.3.1. The Second Tracing Experiment in Spring 1994 (H. Behrens, R. Benischke, W. Käss, M. Zupan).............................295 6.3.3.2. The Fourth Tracing Experiment in Autumn 1995 (M. Zupan)......302 6.3.4. The decomposition of tracers in the spring waters (M. Zupan).......304 6.3.5. The Background Concentrations of the Used Fluorescent Dyes (M. Zupan).........................................................305 6.4. Results with Phages (M. Bricelj).......................,..........................................307 6.4.1. Introduction.....................................................................................................307 6.4.2. Injection data..................................................................................................307 6.4.3. Results..............................................................................................................308 6.4.4. Conclusions......................................................................................................312 6.5. Results with Salts (W. Käss)..........................................................................315 6.5.1. Lithium Tracing Test at Zavrhovc (April 16, 1994)..............................315 6.5.2. Strontium Tracing Test at Mrzli log (April 16, 1994)..........................318 6.6. Mathematical modeling with the Multi-Dispersion-Model (A. Werner & P Maloszewski).....................................................................321 6.6.1. Introduction.....................................................................................................321 6.6.2. The Multi-Dispersions-Model (MDM)......................................................322 6.6.3. The Tracer Tests of the Injection Place Belo Brezno..........................323 6.6.3.1. The First Tracer Test (1993)...................................................................323 6.6.3.2. The Second Tracer Test (1994)...............................................................325 6.6.3.3. The Third Tracer Test (1995)..................................................................327 6.6.4. Conclusion.......................................................................................................328 7. CONCLUSIONS REGARDING THE INVESTIGATION AREA..........329 7.1. Underground connections in dependency to hydrogeological conditions (J. Janež)........................................................................................329 7.2. Underground water connections dependent on hydrometeorological conditions (P. Habič).................................................332 7.2.1. The aim of water tracing by artificial tracers........................................332 7.2.2. Hydrometerological conditions during water tracing tests....................335 7.2.3. Underground water connection Belo Brezno - Hubelj.........................336 7.2.4. Underground connection Belo Brezno - Mrzlek....................................337 7.2.5. Underground connection Belo Brezno - Lijak.......................................338 7.2.6. Underground connection Zavrhovc - Hubelj...........................................339 7.2.7. Underground connection MrzU Log - the Podroteja and Divje Jezero....................................................................................................340 7.2.8. Underground connection Malo Polje - the Podroteja and Divje Jezero....................................................................................................341 7.2.9. Underground connection Lokva (Predjama) - the Vipava (P Habič, V. Armbruster)...........................................................................341 7.2.10. Underground connection Slapenski Ledenik (Nanos Mt.) - the Vipava........................................................................342 7.3. Water Protection measures (J. Janež)..........................................................343 7.3.1. Introduction.....................................................................................................343 7.3.2. Physico-chemical and biological threat to karst superficial and underground waters.......................................................................................344 7.3.2.1. General criteria...........................................................................................344 7.3.2.2. Vulnerability.................................................................................................344 7.3.3. Overview of way and degree of protection.............................................345 7.3.3.1. General criteria...........................................................................................345 7.3.4. Verifying the protection areas related to recent water tracing tests.....346 8. GENERAL CONCLUSIONS............................................................................347 8.1. Methodological aspects of water-tracing experiments (H. Behrens, R. Benischke, W. Käss).........................................................347 8.1.1. Degradation of Uranine during tracer tests............................................348 8.2. Methodological aspects of investigations of single events - The use of the natural tracer silica (V. Armbruster).............................351 8.3. Future aspects (P Habič)................................................................................351 9. BIBLIOGRAPHY................................................................................................354 10. POVZETEK (J. Kogovšek).............................................................................365 10.1 Osnovni podatki...............................................................................................365 10.2 Cilji in potek raziskav....................................................................................366 10.3 Rezultati raziskav.............................................................................................367 10.4 Sledenja v zaledju Mrzleka, Hublja in Lijaka..........................................372 10.5 Sledenja v zaledju Vipave..............................................................................374 10.6 Sklepi..................................................................................................................375 LIST OF THE AUTHORS....................................................................................377 MEMBERS OF ASSOCIATION OF TRACER HYDROLOGY (ATH)....382 1. PREFACE (A. KRANJC) During the 6th SWT at Karlsruhe (1992) the proposal of the participants from Slovenia to organise the next, the 7th SWT in Slovenia, was generally approved. In the autumn of the same year was organised a meeting in Slovenia; a group of experts visited the karst plateau Tmovsko-Banjška Planota conducted by the Slovene specialists who provided appropriate explanations. The final decision to accept the Slovenian proposal passed in Ljubljana. Immediately three committees were designed: the preparatory one (consisting of the members of ATH), the research council (for the research project at Tmovsko-Banjška Planota), and the organising committee. Research activities required for the symposium were carried out in the frame of the international project "Transport of pollutants in karst: tracers and models in different aquifers - field research on Tmovsko-Banjška Planota 1992-1995". Project was mainly financed by the Slovene Ministry of Science and Technology and Ministry of Environment and Physical Planning and, occasionally, by communes and water organisations in the surroundings of Tmovsko-Banjška Planota. The research work including both the field and the laboratory work of the research associates not living in Slovenia, was financed by their organisations or by themselves. More than 50 researchers of various professional profiles from 16 organisations from Austria, Germany and Slovenia co-operated at the research work of the mentioned project. Due to finances, to large number of participants, to their fluctuations, and to questions, opened during the investigations, the course of the research as well as some aims and targets had to be changed, but the essential of the initial plan was kept all the same. To minimise co-ordination questions regular "Preparatory Meetings" were held twice a year in different countries and places, where about 30 researchers gathered every time. As the editor of Acta carsologica and as the Organising Secretary of the 7th SWT I am very glad that both the Classis IV of the Slovene Academy of Sciences and Arts with Editorial Board and the ATH decided that the results of Tmovsko-Banjška Planota investigations will be published in Acta carsologica, with special title "Karst Hydrogeological Investigations in south-western Slovenia". Due to vast number of very different researches, of large amount of data gathered, of great number of authors and of various ways and methods of data interpretation, the preparation of the material for this volume was hard and complicated. But the results prove that it was worth the work and troubles. The editor is deeply grateful, and owes a great debt of thanks to the 7th SWT Editorial Board and to the colleagues from the Karst Research Institute. Map. 1: Visoki Kras (The High Karst) plateaux in western Slovenia (p. 12). Map 2: Tmovsko-Banjška Planota, an overview map (Inštitut za geodezijo in fotogrametrijo FGG, Ljubljana) (p. 13). Merilo 1:450.000 © Geografski inštitut ZRC SAZU o CO > o oc H < LU ^ Z Q LU ILI ^ Ü ^ LU Z CC < CL OQ O CO > O O O Q- i ^ Q_ rf < 0C>(/5 LU o Z Z LU < O m o o o Ui «M Oi- fSo §i cri— m" y LU (C lU s < LUZ ncd 0_j l-CL tr Nl-QZ N — O) m (O s. C 3 (T NJ > < O S "So ^ CE ^ N n 13 CC o. t/) o fO o: ro g ^ I s i C 0) o m o > ™ N § I _ ^ >(0 ro Q^ ^ -J ™ d § C3 >0 LL ns o C « I •S « h» O) fi ^ s oj ca P g g C >o il o s 's > 5 0) M O) ^ d) ■a 5 5 C5 C3 ~ .'A "o ^ OJ ffl tr* (U E 5) o N (D T3 O Q) O) ns N £ o ^ ^ g = o .m 5. 5 SS ^ ■a ® 2. NATURAL BACKGROUND 2.1. PHYSICAL GEOGRAPHY OF TRNOVSKO-BANJSKA PLANOTA (P. HABIČ) The test area of the 7"' Symposium on Water Tracing includes a part of High Dinaric Karst in the western Slovenia; it is bounded by the valleys of the rivers Soča, Idrijca, Vipava and Pivka. From the Soča river in the north-west up to the sinking karst rivers Pivka and Ljubljanica in the south-east, there are, within otherwise uninterrupted landscape of the High Karst, morphologically slightly different areas as for example Banjšice, Trnovski Gozd, Črnovrška Planota, Hrušica and Nanos. This area of the High Karst is usually referred to as Trnovsko-Banjška Planota (TBP). The belt of the High Karst between the northern border of the Adriatic Sea and eastern foot-hills of the Southern Limestone Alps narrows the most in the western Slovenia. A block of carbonate rocks belonging structurally to the Dinaric Mountains, is from 10 to 15 kilometres wide and about 50 km long, covering roughly 700 km^ of the surface. Deeply karstified Cretaceous and Jurassic limestones and Triassic dolomites prevail; towards the north-west they underhe younger, mostly Eocene flysch rocks. Flysch encompasses karstified limestones of Trnovski Gozd and neighbouring plateaux in the southern and eastern side thus acting as a partial, hanging hydrogeological barrier. In the north the High Karst is surrounded by mostly impermeable Middle and Lower Triassic, partly also Permian and Carboniferous rocks. The valleys of the Belca, Idrijca, Trebuša, Hotenka, Kanomlja and Zala rivers are cut into these rocks. In their river basins, specially on the Vojsko Plateau, there are some sinking streams, caves and karst springs. For several reasons this final edge of the High Dinaric Karst between the Vipava valley and the foot-hills of the Julian Alps dissected by the valleys of the Idrijca and Soča rivers was chosen as a test area of Association of Tracer Hydrology for the preparation of the 7"' International Symposium on Water Tracing. From a physiographic and hydrogeological point of view this is a relatively well-confined mountainous karst area bounded by lower, non-karstic margin regions from almost all the parts. The rainfall from this entire area sinks into deep karst aquifer feeding abundant karst springs located at its foot along the tributaries of the Idrijca, Vipava, Soča and Ljubljanica rivers. Smaller sinking streams may only be found in the western and eastern side of Trnovski Gozd. In the valleys on its border major karst springs are distributed, such as Mrzlek, Avšček, Kajža and Vogršček along the Soča; Lijak, Hubelj and Vipava along the Vipava; and Divje Jezero, Podroteja and Hotešk along the Idrijca. The rivers Idrijca, Soča and Vipava belong to the Adriatic water system, and Ljubljanica to the Black Sea basin. Thus the underground watershed between the Adriatic and Black Sea is found within the High Karst. Karst springs in the border of the High Karst are captured for water supply of villages in Vipava valley, on Goriško and along the Soča and Idrijca. As these are the only abundant sources of drinking water in western Slovenia their karst background must be protected against pollution. Due to hydro-graphical complexity within this karst aquifer, it has not yet been possible to define the extent, size and capacity as well as threat to each karst spring separately. For the same reason, protection measures were not introduced separately but for the area as a whole. Previous hydrological and geological researches indicated the main drainage directions of karst waters, but a series of unsolved hydrological questions remained. To solve these would provide better exploitation and better protection of water resources. Intensive karstification is evidenced by solution channels, runnels and karren on bare rocky surfaces. There are numerous, karst dolines and ouvalas, more than 100 m deep, and many caves and shafts, some more than 300 m deep. In the ice-cave Velika Ledena Jama v Paradani cavers have reached a depth of almost 700 m. This external image of intensive karstification is complemented by hydrological indicators. After rainfall the discharge in springs increases rapidly and also decreases relatively fast. Deep karstification is shown also by the location of karst springs in the bottom of the valleys and by their deep siphon outflow passages; at Mrzlek they are below the Soča riverbed, in Divje Jezero cave divers reached more than 100 m below the Idrijca valley without getting to the end of this typical Vauclusian spring. Karst relief dominates over the entire area. Among the elevations typical cone-shaped features prevail; isolated peaks are distributed in levels over the central ridge but they appear also on lower, more flattened borders. Between the elevations there are deep dry valleys with dolines. Such a relief neutralises the superficial watershed. Deep fluvial valleys are cut on the border of the High Karst plateau only. The bottoms of river valleys are from 50 to 300 a.s.l. and this is also the altitude where are the lowest probable free surface springs. Central karst plateaux reach altitudes from 600 to 1500 m a.s.L; the slopes of the valleys are steep and high. The south-western edge of the High Karst from Razdrto past Vipava and Ajdovščina up to Gorica is nearly vertical and at the foot of limestone walls there are recent and fossil scree slopes above the Vipava valley. Carbonate rubble and breccia on the flysch base represent smaller porous aquifers. Calcarenite, breccia and conglomerate inliers of carbonates in Eocene flysch along the Soča to the western border of Banjška Planota represent aquifers of karst and fissure porosity of local importance. In the eastern and western side of Trnovski Gozd, specially on Banjšice, along northern border of Nanos, near Črni Vrh and on Pivka they contribute a part of waters to the central karst aquifer which is seen also in the hydrochemical properties of related springs. Orographic properties of the surface are controlled by geological structure and by younger tectonic movements and by geomorphologic development from the Middle Pliocene onwards. The main ridge of the High Karst trends from north-west to south-east, but it is slightly displaced towards the north-east border. The highest elevations in the central part of Trnovski Gozd are the peaks named Veliki Golak (1495 m) and Mah Golak (1480 m). On the southern and western border of the main ridge of Trnovski Gozd there are some marginal shelves preserved as remains of former, broader planations. There were found the remains of fluvial gravel deposited by waters from neighbouring Pre-alpine valleys when the rivers flowed over the actual High Karst towards the Adriatic Sea. Transverse and also longitudinal dry valleys are downcut into an old, levelled surface. The most expressive is the valley of Čepovan, 20 km long and more than 300 m deep. It widens in its southern part and passes into a smaller karst margin polje near Grgar (280 m). The lowest exit of Grgar lies in the continuation of a dry valley on Preval, 336 m a.s.l. between Sveta Gora (681 m) and Škabrijel (546 m) which is almost 300 m above the present riverbed of the Soča near Gorica. The bottom of the dry valley reaches the highest point in the north of Čepovan, at 620 m and it lowers to 540 m in its northern border near Vrata to remain hanging in a steep edge, 270 m above the Idrijca riverbed. The valley of Čepovan is a natural border between Banjšice to the west and Trnovski Gozd to the east. The highest main ridge of Trnovski Gozd between Paradana, Mala and Velika Lazna and Krnica is cut by a transverse dry valley. Similar are transverse valleys in the south-eastern side of Trnovski Gozd between Mala Gora and Kovk and between Črni Vrh and Col. Transverse dry valleys are important for traffic and they are used for local and forest roads. However, main traffic roads lead along the High Karst by the valleys of the Idrijca and Vipava. An important cross traffic road passes along the western border of the High Karst by the Soča valley between Gorica and Tolmin. There is little soil on the karstified hmestones of Trnovski Gozd (The Wood of Trnovo) and wood prevails there as its name indicates. The rather humid mountainous climate is favourable for fir and beech trees. These two species comprise Vast fir-beech forests. On the highest ridge of Trnovski Gozd the trees are exposed to strong wind, the bora, and therefore the trees are lower with typically shaped branches bent and blasted by the wind. The highest Golaki displays the features of upper tree limit. Instead of beech, dwarf pines appear there. This species may also be found at the bottom of deep karst dolines where cooler air accumulates. In these frost-places the vegetation belts are inversely distributed. A belt of beech is followed downwards by a belt of spruce and at the bottom of doline there is a belt of dwarf pines; in the deepest karst dohnes, in particular at the entrance to ice-caves, a belt of mountainous meadows without trees may even appear. These vegetation specialities of Trnovski Gozd very early aroused the attention of experts. Forest management, that is regulation and protection of karst woods accompanied by a suitable exploitation, has a several hundred years long tradition. From a climatic point of view the High Karst is a typical transitional area between the Mediterranean climatic influences of the Adriatic and the continental and Alpine climatic region of inner Slovenia. The high karst ridge is a sort of barrier against the frequent south-western wind that brings the humidity from Mediterranean. As humid air lifts over the first mountainous barrier it releases heavy precipitation. Thus the central part of Trnovski Gozd receives annually more than 3000 mm, and the maximal daily rainfall may even surpass 300 mm. The mean annual temperature varies from 7 to 9° C. The mean air temperature in January is about -2° C, and in July about 16° C. On Golaki where the upper tree limit is at 1440 m a.s.l. the mean air temperature in July is about 12° C. In the cold half of the year cool air from the south-eastern side frequently passes from the High Karst towards the Mediterranean; this occurs as a strong wind in gusts, called the bora, which may reach more than 200 km/h in the Vipava valley and in dry transverse valleys. Relatively early in autumn snow falls on the peaks of Trnovski Gozd and in spite of some thawing during the winter it may be found in deep dolines up to May, and in caves with large entrances throughout the summer. In many ice caves the local people used to cut out the ice and transport it to the valley and to Triest and Gorica to chill food and drink in times when electric refrigerators did not yet exist. On the border of Trnovsko-Banjška Planota and on Nanos the trees were cut down. At first the land was used for pastures, and later permanent settlements grew. The most dense population is found on Banjšice as far as Grgar to the south and Čepovan and Lokovec to the north. On flysch rock there is more soil which favours agriculture. On Lokovec north from Čepovan and around Trnovo, Voglarji and Lokev south from the Čepovan valley there are less cultivated surfaces. Slightly more soil is provided by disintegrated cherts that occur as lens-shaped inhers in Cretaceous and Jurassic limestones. The same may be said for the inhabited south-eastern part of Trnovski Gozd where modest farms are scattered on the border of the plateau from Predmeja, over Othca, Kovk, Gozd and Križna Gora to Col, Podkraj and Vodice. Some scattered farms may also be found to the north of the main ridge of the High Karst near Zadlog, Črni Vrh and Lomi. In the western border of Nanos the former Vast pastures are more and more overgrown by vegetation and only two farms remain there. Sparse population and low agricultural activity are relatively favourable to protecting the karst aquifer. But, together with endeavours to protect karst waters, there exists a wish to increase the economic development of these villages. In the past they mostly survived by cattle breeding and forestry. Later local people travelled to work in the valleys, and in factories in Gorica, Ajdovščina, Vipava and Idrija; in recent years they try to get work at home in craft and smaller industries. Former rainwater reservoirs are replaced by piped water supply; water is pumped from lower lying springs and increased quantities of waste water flow mostly untreated, underground. The economic development on Trnovsko-Banjška Planota must as soon as possible be co-ordinated with protection of this important karst aquifer which is capable of supplying the larger and more inhabited valley area of the High Karst around Vipava, Gorica and Idrija with drinking water. 2.2. HYDROLOGY (N TRIŠIČ) 2.2.1. Basic description of the area The area of the Trnovski Gozd, the Banjšice, the Nanos, and a part of the Hrušice plateaux hydrologically belongs to the Soča river basin extending over approx. 2000 km^ in Slovenia, which is almost one tenth of Slovenian territory (Fig. 2.1). The river basin stretches from the central part of the JuUan Alps over the pre-Alpine mountains, the territories of Cerkljansko and Idrijsko, the high karst area of the Nanos and the Trnovsko-Banjška Planota, the flysch area of the Vipavska Dolina, to the level gravel-sand accumulation of the Soča and its tributaries on Italian side. In Slovenia, the Soča river basin borders on the Upper Sava river basin, and the Ljubljanica and the Timava river basins, and on Itahan side, on the Taghamento river basin (Fig. 2.1). The strongest tributaries of the Soča are two left tributaries, the Idrijca and the Vipava, which drain the area of Idrijsko and Cerkljansko, the high karst area of the Trnovsko-Banjška Planota, the Nanos, a part of the Hrušica, and the flysch area of the Vipavska Dolina valley. The entire area can be studied as two separate hydrological units, one of which as the catchment area of the karstic springs of the Vipava, and the other one as the catchment area of the karstic springs at the rims of the Trnovsko-Banjška Planota. POREČJE SOČE V SLOVENIJI - SOČA RIVER BASIN , LEGENDA - LEGEND Avtomatske fxtetage 1961-1990 XI XII Fig. 2.5: The average monthly precipitation in the catchment area of the Idrijca and the mean monthly discharges (1961-1990). Tab. 2.4: The 1961-90 data for the Idrijca - LP Podroteja profile. F Precipitation Evaporation Precipit. runoff Q, difference km^ Q (mVsec) (mVsec) (mVsec) (mVsec) (mVsec) 112.84 9.20 2.21 6.99 9.75 +2.3 Tab. 2.5: The characteristic discharges of the 1961-90 period at the Idrijca- Podroteja, and their ratio (m^tsec). ^min ^me;in ^max Q : Q ^min mean 0.84 9.29 306 1 : 11 : 364 The ratio between the maximum and the minimum discharges of the Idrijca at the LP Podroteja gauging profile is so high exactly due to the surface part of the catchment area (Tab. 2.5). Tab. 2.6: The average annual precipitation in the catchment area of the Idrijca (mm). Črni Vrh Idrijska Bela Mrzla Rupa Vojsko 2589 2623 2784 2450 Lijak - Šmihel In the gauging profile at the Lijak - Šmihel station discharges are registered of the periodically active springs, which are only an overflow of high waters from the catchment area of the Mrzlek spring. The hydrauHc Unk between these two springs has been confirmed. At low waters, the water level of the Lijak oscillates parallel to the oscillation of the water level in the Solkan hydropower-plant reservoir, and the gradient towards the Soča is minimal. When the spring Lijak is active, the water table in its karstic catchment area rises even more than by 40 m. There were no continuous observations of the spring in the 1961-90 period, therefore, the characteristic data for that period are missing. The highest registered discharge is 32.6 mVsec, but a greater part of a year the spring is dry. The catchment area of the Lijak can also be considered as a bifurcation area since the high waters of the spring also gravitate towards the Vipava, and when the spring is not active, all the waters from the catchment area gravitate towards the spring Mrzlek, i.e., to the Soča. The regime of the Lijak spring demands a special interpretation of water balance, since the high water waves exert impacts on the discharge regime of the lower section of the Vipava, but the size of its belonging catchment area cannot be defined. The correlation with the Hubelj spring was studied for the Lijak spring; it shows a strong dependence between the regimes of both springs (MUZIC 1986). Hubelj - Ajdovščina The gauging station is located less than 2 km downstream of the Hubelj spring. At the spring itself, water is tapped for the water supply, which reduces the volume by 50 to 150 1/sec. The orographically determined size of the catchment area (F = 85.25 km^) for the gauging station on the Hubelj is too big, therefore the calculation of water balance gives so great a difference between the calculated and the gauged runoffs (Tab. 2.7). The theoretically calculated size of the belonging catchment area measures approx. 50 km^ (STAHL 1994). Tab. 2.7: The 1961-90 data for the Hubelj - VP Ajdovščina profile. F Precipitation Evaporation Precip. runoff Q. difference km^ Q (mVsec) (mVsec) (mVsec) (mVsec) (mVsec) 85.25 6.64 1.76 4.89 3.03 -1.9 Tab. 2.8: The characteristic discharges of the 1961-90 period at the Hubelj - VP Ajdovščina, and their ratio (m^/sec). Q Q mean Q ^max Q . mm : Q mean : Q 0.185 3.03 59.5 1 : 16 : 322 The coefficient is high and speaks in favour of the fact that in the case of the Hubelj spring its maximum discharge is not suppressed (Tab. 2.8). Tab. 2.9: The average annual precipitation heights in the catchment area of the Hubelj (mm). Ajdovščina Lokve Otlica Podkraj 1553 2381 2409 2179 The largest quantity of precipitation in the catchment area of the Hubelj spring falls in November, on average, while the mean monthly discharges of the Hubelj are the highest in April when snow begins to melt (Fig. 2.6 and 2.7, and Tab. 2.9). The distribution of the maximum discharges in all three discussed gauging profiles do not offer any law; but from the distribution of the minimum discharges, the influence is clearly visible of the water reserves from the snow cover, even on the minimum discharges in the summer months. The minimum discharges of the Hubelj and the Vipava occur in February, and in September or October, and they are practically equal, while the autumn minimum discharges of the Idrijca are essentially lower than those in February (Fig. 2.8). The quoted basic hydrological conditions of the discussed area and the springs already represent the hydrological problems which are typical of the karstic hydrological systems (Fig. 2.9). Besides the inaccurately determined sizes of the catchment areas and the directions of water streams in the system, an additional uncertainty occurs in the area of the Trnovski Gozd and the DISCHARGES HUBELJ-AJDOVSCINA PRECIPITATIONS PODKRAJ 3.5 3 I" V VI VII Wll IX mounttily average 1961-1990 Fig. 2.6: Mean monthly discharges of the Hubelj and mean monthly precipitation in the 1961-90 period. Hubelj - AjdovSčin« 1961 • 1990 20 2S "min ~"max-*-™sre(J. Fig. 2.7: The lines of the 1961-90 discharge duration of the Hubelj at the VP Ajdovščina gauging station. DISTRIBUTION OF MINIMAL MOUNTHLY DISCHARGES (1961-1990) IDRIJCA-PODROTEJA III IV VI VII VIII IX XI XII Fig. 2.8: The distribution of the minimum monthly discharges in the 1961-90 period. HIDROGRAFSKA IN HIDROLOŠKA MREŽA HYDROGRAPHYC AND HYDROLOGICAL NETWORK 8610 o LEGENDA - LEGEND SlPRA VODOTOK - POSTAJA CODE RIVII! - CAUGCTG STATION BISO 83-16 B630 64S0 8456 84130 B500 854 S 6647 8849 85«0 8565 8590 SBOD 8808 8603 8SI0 8630 8640 8BD0 8S60 8670 Soča - Solkan Idrijce ■ Petnar Idrijca - Podrotejn Mrljoa - Hotescek Cerknica - Cerkno Trebuse - Dol.TrebuSa Be6a - Baea pri Madnjju Bel&£tcB ~ Sukovj« Lokva - PredjBma Pod (aronera " Vipava Vipava ~ Vipava Vipava - Planino Vipava - Dornbark Vipava ~ Miren Bela - Saaabor Bela - Vipava MaÄilniii -- Podnanos Hubelj - Ajdovseina Branlca ~ Branik UJak - Smiliel Ujak - Volčja Draga VogrfiCak - Baiovljak Fig. 2.9: Hydrographie and hydrologieal network. Banjšice, which further aggravates the comprehension of hydrological conditions. These are the unspecified discharges of the Mrzlek spring which flows into the Soča in the area of the Solkan HPP reservoir and, thus, cannot be directly gauged. 2.3. THE CLIMATE OF THE TRNOVSKO-BAN JŠKA PLANOTA (J. PRISTOV) 2.3.1. Meteorological conditions The Trnovski Gozd, the Banjšice and the Nanos are the first mountain barrier (the altitudes of peaks between 1000 and 1500 m above sea level) on the way from the Mediterranean, or the Northern Adriatic, towards the north and the north-east. Naturally, there is the Kras plateau before it, yet, it mainly does not exceed the altitude of 600 m. Therefore, the orographic precipitation are modest on the Kras, but they already become rather abundant at the barrier running from the Banjšice to the Nanos, and they are the most abundant at the southern part of the Julian Alps. There, the altitudes of the peaks already reach approximately 2000 m, and the average annual precipitation already amounts to 4000 mm, which is the highest value in the Alps. This barrier represents a divide between the Mediterranean and the Alpine climates. The Vipavska Dolina and Goriško region, both located at the southern rims of the Trnovski Gozd, are under the intense influence of the Mediterranean climate. Yet, the Trnovski Gozd, the Banjšice and the Nanos already have the real Alpine climate with the abundant snow during the rather cold winters. The precipitation are abundant all year round, with the explicit maximum in October and November. In the heart of the Trnovski Gozd, i.e. the area of Golaki, they exceed the precipitation average over the period of 30-years, which is 3000 mm, and also the entire area of the Banjšice, the Trnovski Gozd and the Nanos, annually receives over 2000 mm of precipitation, on the average. The most intense precipitation very often occur in October, up to 900 mm (Vojsko 888 mm; Mrzla Rupa 855 mm; Otlica 702 mm), but on the average, October is not the wettest month. Namely, oscillations of precipitation quantity are extremely sharp in this month: on the one hand, the monthly precipitation extremes occur with heavy precipitation, and on the other, this month often receives the minimum precipitation and sometimes - although it happens rarely -they do not fall at all (in 1965). November is the month with the largest average quantity of precipitation, yet the oscillations are not as sharp as in October, and therefore, the annual extremes do not occur in this month. Although rarely, but very heavy precipitation also occur in the month of September. It is typical of autumn precipitation that they are very intense in shorter periods, and they are often unevenly distributed over the discussed area. It happens that the intensity of precipitation in individual areas differs a lot (the ratio of 1:5), which is not the case with the convective precipitation, but with the orographic precipitation related to the front system. For determining the quantities of precipitation by individual precipitation situations, a rather dense network of precipitation gauging stations would be necessary, or, great errors could occur due to the intensely agitated precipitation area. The Trnovski Gozd receives the majority of precipitation in autumn, when the sea is still rather warm, and the very warm and humid air, driven by the SW winds, flows in from above the Mediterranean. When on its way during the precipitation situation this air reaches the first higher mountain barrier, it must ascend to pass it, which results in the orographic precipitation. Such situations often occur during the generation of secondary cyclones in the Genoa bay or above the Northern Adriatic. It is in autumn and spring when the secondary cyclones are most frequent, only that the warm air in autumn contains quite a lot of humidity. The humidity of air is considerably lower in spring due to the cooler northern Mediterranean, and therefore, the orographic precipitation are not so abundant. The monthly quantity of precipitation considerably exceeds the evaporation. July is the least wet month, and even then, more than 160 mm of precipitation fall; concurrently, it is also the month with the most intense evaporation, when the potential evapotranspiration (ETP) on the Nanos amounts to 130 mm, and Ce at Cepovan, to 122 mm (Fig. 2.10 and 2.11). Since the monthly precipitation, on the average, always exceed the ETP, it is assumed that the actual evapo- Fig. 2.10: Mean monthly values of potential evapotranspiration (ETP), precipitation (RR) and corrected precipitation (CRR) on the station Cepovan. 250 ■ ETP(iTm) BRR(mm) Fig. 2.11: Mean monthly values of potential evapotranspiration (ETP), precipitation(RR) and corrected precipitation (CRR) on the station Nanos-Ravnik. transpiration (ET) equals to the potential evapotranspiration (ETP); therefore, in the continuation of this paper, only the term evaporation is used and is equalised with the ETP. On the average, more than 300 mm of precipitation fall in November at Vojsko and Mrzla Rupa, but only 15 mm evaporate. In October, the same area receives more than 250 mm of precipitation, but only about 35 mm evaporate. On the average, the greatest discharges occur in October, although the greatest quantity of precipitation fall in November. The air in the inland of Slovenia is already so cold in this month that the higher altitudes of the Trnovski Gozd are already covered with snow, which is immediately manifested in the reduced discharges. The secondary maximum of discharges occurs in the spring months when the snow cover is melting. As it has already been mentioned, the Trnovski Gozd and Nanos represent the divide between the Mediterranean and the Alpine climates. When the inland of Slovenia is filled with the cold air from the north or the Northeast, great temperature differences originate at the foregoing barrier, as well as great pressure gradients. When the air descends from above the Trnovski Gozd and the Nanos towards the Vipavska Dolina and the Kras, it is adiabatically warmed, yet, it is still cooler than the air above the northern Adriatic. The result of this temperature difference is that the cold air cascades down the slopes, and reaches great velocities, while due to the agitated landforms, violent turbulences are generated. This strong wind is known under the name of bora, and reaches the velocities of up to 200 km/h with individual gusts. Relatively frequent occurrence of the bora, of smaller velocity of course, is also the cause that the air above the Kras and the Vipavska Dolina is dryer than the air above the other regions of Slovenia. Such relatively dry atmosphere provides for the natural drying of ham which is famous as a speciality under the name kraški pršut (i.e. the karstic crude ham). 2.3.2. The water balance The equation of water balance P = Q + E + N* + R (1) expresses that in a specified area the precipitation, P, equal the sura of water discharges, Q, evaporation, E, the changes in water reserve, N*, and the water captured for the biological and industrial consumption, which is pumped from the studied area, R. In our case, the amount of the pumped water is small in comparison to the possible errors at precipitation gauging and making the precipitation maps, and therefore, it is not directly taken into consideration. For the longer periods it can be assumed that the changes in water reserves in an average year are negligible, and the equation is reduced to the following items only: P = Q + E (2) which means that the precipitation in a specified area equal the sum of discharges and evaporation. For the needs of evaluating tracing experiments we wished to obtain water balance for the short periods, i.e., for the individual precipitation situations, or, at least for the periods of several months during which the individual tracing experiments were performed. The results of water balance for the shorter periods were not encouraging although we tried to do our best when making the basic maps. For the precipitation map of wider area of the Nanos and the Trnovsko-Banjška Planota, the data were made use of from 40 precipitation stations where daily precipitation were gauged at 7 hrs (Archives of the Hydrometeo-rological Institute, Slovenia). In individual precipitation situations, very explicit minor precipitation cells occurred, which were impossible to be correctly presented through such low density of precipitation gauging station network. During the relatively stationary precipitation situations, the differences of precipitation between individual areas (from the north towards the south, or, from the west towards the east), even reached the ratio of 10:1. At such sharp precipitation changes, errors occur in the making of precipitation maps, especially at the determining of precipitation for the relatively small contributing areas, particularly if the watersheds are not strictly defined. The equation of water balance in which the precipitation are equal to the sum of water runoff and evaporation, apply only in case when the changes in the water reserve N* are negligible, which is almost impossible to expect at precipitation situations. With heavy precipitation the water reserve in the ground considerably increases. In the late autumn months, the higher altitudes of the Trnovski Gozd are already under the snow covcr which can contain quite large water quantities. To avoid all these troubles, the 30-year water balance was taken as a basis. Let it be assumed in this case, that the water reserve at the end of the period equals to that at the beginning, sincc the difference in an average year is minimal in so long a period, thus, it means N* = 0. Also at the gauging of precipitation, the casual errors arc eliminated by averaging; however, the systematic errors remain, which can be considerably reduced by applying supplementary procedures (precipitation correction due to wind, etc.). Due to the considerable oscillation of annual precipitation in the 30-year period, the water balances were determined also for the 5-year and the 2-year periods, and it was also assumed that N* was negligible. Although this is a rough premise, yet, it is acceptablc were the accuracy taken into consideration, of the precipitation gauging, which is particularly problematic at the higher altitudes due to wind, while the terrain configuration does not allow that the vertical precipitation gradients be directly applied. Precipitation determining Precipitation are gauged with a gauge of Hellmann type which collects too little precipitation in windy weather. The experiments proved that, at wind speed of more than 5 m/scc, only 22 % of the actual snow precipitation are gauged, and 87 % of the actual rain precipitation (YANG et al. f994). Experiments on precipitation gauging in wind conditions were not carried out in Slovenia; therefore, we assumed the WMO intercomparison results. For the stations registering wind observations, force of wind was reduced for each precipitation day, to the altitude of Hellmann's gauge, and then, the adequate coefficient or the anticipated precipitation quantity was calculated. On the basis of gauge locations and direct obstacles, the precipitation stations were ranked into classes. For each class, the monthly and annual coefficients for the correction of precipitation were specified, on the basis of data from the stations with wind observations. By means of these coefficients, the quantities of precipitation were also corrected for the stations without wind observations. Because the precipitation in Slovenia are heavier than in the places where the experiments were performed, it is assumed that also the rain drops and the snow flakes, on average, are shghtly greater and heavier, respectively. Therefore, we reduced the corrective coefficients by 20 % for the places at the altitudes between 1000 m and 1500 m, and by 35 % for the places lying higher than 1500 m. Thus, the corrective coefficients amount to between 1.01 and 1.05; for the very exposed locations only, between 1.05 and 1.08; for the exposed locations above 1000 m in the area of the Nanos and the Trnovsko-Banjška Planota, up to 1.14. Besides the increase of precipitation due to wind, we also toolc into account the increase of precipitation due to the gauge moistening. Whenever the gauge is emptied, a slight amount of water remains on the bottom and the sides of container. Following the results of laboratory testing, we took for the precipitation days with more than 1 mm of precipitation, the correction of 0.3 mm for a rainy day, and the correction of 0.15 mm for a day with snow precipitation. For all the precipitation maps, the corrected precipitation data were made use of. In the making of precipitation maps (Fig. 2.12), the vertical precipitation gradients were not taken into account (a rather even increase of precipitation with the altitude), but the distribution was assessed subjectively, depending on the terrain configuration and precipitation data. Namely, it turned out that certain lower-lying places had received more precipitation than the higher-lying ones (Mrzla Rupa, 930 m above sea level - 2940 mm; Vojsko, 1070 m above sea level - 2800 ram; similar situation occurs in some other stations). Fig. 2.12: The 1961-90 period precipitation map (mm). The quantity of precipitation depends on the location of the valleys and mountain ridges. Certain laws were taken into consideration which, however, are based on the physics related explanation (the narrow valleys lying perpendicular to the direction of SW winds receive abundant precipitation, much more than the valleys lying in the direction of SW winds, especially if these valleys are located in the lee of mountain ridges, etc.). Evaporation 300-400 400-500 300-600 600-650 6SO-700 700-750 > 750 Fig. 2.13: The 1961-90 period evaporation map (mm). For the calculation of runoffs on the basis of precipitation and evaporation, an evaporation map is indispensable. Since the precipitation in our case are much more abundant th an the evaporation, considerable simplifications are applied to the evaporation data; yet, approximately equal accuracy is obtained with both maps. Calculated for the chmatological stations was the potential evapotranspiration (ETP), following the corrccted Penman method, by making use of the daily values of four weather parameters: air temperature, relative humidity of air, wind, and insulation (DOORENBOS et al. 1986). Since the monthly precipitation above the discussed area are always greater than the calculated ETP, we assumed that the evaporation is equal to the ETP, only for the lower-lying Kras plateau where the stone surface dries fast, we reduced the ETP by 10-15 % to obtain the evaporation. The annual quantity of precipitation on the Trnovski Gozd is often greater than the evaporation. If the accuracy of precipitation gauging and simplification are taken into consideration, the accuracy of evaporation data is soon satisfactory. For the areas where not enough data were available, we applied the vertical gradients of evaporation which had been calculated on the basis of data from this area. The difference between the actual surface area and its horizontal projection which is presented on the maps is taken into account in such a way that the calculated evaporation is being evenly increased with the altitude, and at the altitude of 1500 m, the addition amounts to approx. 10 %; on the plateaux, this increase is not taken into account (Fig. 2.13). Runoff The precipitation map (Fig. 2.12) and the evaporation map (Fig. 2.13) were digitised and then, the evaporation field was deduced from the precipitation field. Thus, we obtained a runoff map, specified in mm. Since all the maps were made for an average year in the thirty-, five-, and two-year periods, the values presented in mm also represent the annual runoff in htres per square meter (Fig. 2,14). This map has similar deficiencies as the precipitation map, because the values of precipitation are much greater than the values of evaporation. The calculated discharges for various gauging profiles are obtained from the runoff map by means of planimeter on the basis of hypothetical watersheds. The comparison of the gauged discharges with the calculated discharges and their deviations are a warning signal for the problems of watersheds and the deficiencies in the analysis of individual parameters. Usually, the greatest relative deviations occur at very small river basins, while at larger river basins, the relative correspondence is much better. Fig. 2.14: The 1961-90 period discharge map (mm). 2.4. GEOMORPHOLOGIC REVIEW OF TRNOVSKO-BANJŠKA PLANOTA (P. HABIČ) 2.4.1. General orographic-hypsographic properties Among the valleys of the Soča, Idrijca, Pivka and Vipava rivers in western Slovenia lies a mountain ridge of the High Karst, called Trnovsko-Banjška Planota and sometimes Trnovski Gozd for short. Tlie north-western part of the High Karst comprises a scries of morphologically rounded units called, from the Soča valley towards Pivka or Postojna basin in the south-east, as Banjšice, Trnovski Gozd, Križna Gora, Javornik, Crnovška Planota, Hrušiea and Nanos. Most of this entirely karst surface reaches altitudes between 800 to 1200 m; there are some dry valley incised in it and also some wider depressions, and at its border the surface is slightly lower. Only single peaks in a central ridge of Trnovski Gozd reach more than 1200 m a.s.l.; the highest of these is Veliki Golak (1495 m), in Javornik the highest is Srednja Gora (1275 m) and on Nanos it is Suhi Vrh (1313 m); the Črnovrška Planota hes mostly at altitudes between 600 and 800 m, and the same may be said for the western border of Banjšice; the lowest is its southern border where the bottom of a margin karst polje near Grgar lies between 285 to 300 m a.s.l (Fig. 2.4.1). On the border of the High Karst the relatively narrow Soča valley is cut the deepest; near Gorica where it broadens to the Gorica Plain it lies at about 50 m a.s.l., but only 30 km upstream at the confluence with the Idrijca near Fig. 2.4.1: The orographic units of the High Karst in western Slovenia. Most na Soči it is 150 m a.s.l. The Idrijca valley rises for about 400 m up to the confluence with the Belca which is deeply cut in the northern border of Trnovski Gozd. The watershed between the valleys of the Belca and Trebuša, in the NE side of Trnovski Gozd lies about 1050 m high; the Trebuša flows into the Idrijca at 190 m a.s.l. Both valleys are relatively narrow, the slopes in the southern side of the highest part of Trnovski Gozd being higher and steeper, sometimes even vertical. Even more deeply downcut is the Vipava valley on the southern side which rises from its confluence with the Soča at 30 m a.s.l. up to the Vipava spring below the western slopes of Nanos at only 100 m a.s.l.; along its tributary Močivnik the watershed with the Pivka near Razdrto hes at 595 m a.s.l. The valley of Vipava is in fact a low undulating surface on Eocene flysch between the Trieste-Komen Karst in the south and the High Karst in the north. Its valley bottom is relatively narrow, except between Vipava and Ajdovščina. The contrast between the low flysch hiUs in the north and the steep and sometimes even subvertical slopes of the High Karst is a remarkable sight. Limestone overthrusted on flysch is exposed to intensive mechanical weathering and breakdown; therefore tectonic breccias, debris and breakdown blocks are accumulated at the foot. The south-eastern karst border of the western High Karst comprises the valleys of the Nanoščica in a flysch part of the Postojna basin, from 510 to 600 m high, and a gap (Postojnska Vrata) between Hrušica and the Javorniki -Snežnik Mountains, between 600 and 750 m a.s.l.; further on there is the karst polje of Planina and a part of Notranjsko, or Hotenjsko Podolje between Logaško Polje and the valley of the Zala stream which flows near Podroteja into the Idrijca. Notranjsko Podolje at Planinsko Polje lies at about 450 m, but elsewhere the elevations between 500 and 650 m prevail. In the region between Kalce, Hotedršica and Godovič there is a karst plain up to two km wide in the Idrija fault zone. On its southern side it is bounded by the 300 m high steep edge of Hrušica and Javornik and on its northern side by Rovtarsko Zibrška Planota. To the east of Trnovski Gozd and Križna Gora the High Karst abruptly lowers to Črnovško Zadlaška Planota, up to 5 km wide, which forms the higher and broader part of Hotenjsko Podolje. The studied part of the High Karst is composed of Cretaceous and Jurassic limestones and Upper Triassic dolomites that belong to the Trnovsko Hrušiški nappe within a thrust structure of western Slovenia. The carbonate rocks are thrust over the layers of Eocene flysch and over-thrusted blocks are fractured and tectonically displaced along longitudinal Dinaric and transverse faults (see chapter 2.6). The western part of the High Karst in the region between the Idrijca and Vipava rivers is from 10 to 15 km wide as an uniform block of karstified limestones and dolomites; between the Soča and Pivka rivers it is about 50 km long and covers roughly 700 km^ of karst surface which is prac- tically from all the sides bounded by lower fluvial areas. Flysch rocks encompass karstified limestones as a partial or complete hydrogeological barrier on the west, south and east. On Banjšice to the west of the High Karst flysch is preserved as a thin cover over karstified limestones and in some places the karstified base outcrops; however it mostly acts as a hanging hydrogeological barrier underlain by a typical karst circulation. In the north the High Karst is surrounded by impermeable Middle and Lower Triassic but also Permian and Carboniferous rocks. The river Idrijca and its tributaries the Belca, Zala, Ka-nomlja, Hotenja and Trebuša incised their superficial beds in them. Taking into account the trend of the Idrijca headwater valleys and also corresponding hypsographic conditions we may assume that the Idrijca, Belca, Nikova and Kanomlja once flowed towards the south-east over Črnovrška Planota and by Hotenjsko Podolje into the formerly superficial Ljubljanica (MELIK 1963). It is supposed that river piracy in impermeable rocks around Idrija and karstification in the Ljubljanica riverbed contributed to diversion of the Idrijca headwaters into the Soča. GORENJE S. A e.'^ 7.» 8.0 Fig. 2.4.2: The sinking streams and caves near Predjama. Legend: 1 - overthmst, 2 - cave passage, 3 - sinking stream, 4 - Adriatic-Blacl Fig. 2.4.5: Morphographic section through High Karst between Vipava valley and vale of Hotedrščica. 1 the base of Trnovo nappe. Smaller karst depressions developed in three hort belts in Gornje and Dolnje Lome and near Podjesen where the superfi-ial waters from nearby flysch disappear. In older phases the flyseh waters ontributed to the formation of the karst plain in limestones at the border of olomite. But karstified limestones in a flysch basement shortened their uperfieial flow. The north-eastern part of Črnovrška Planota is formed in cetaceous limestones as a doline-like plain. The superficial waters from the resent Idrijea and Belca headwaters probably contributed to its former lanation when they had flowed superficially south-eastwards and helped to evelop Hotenjsko Podolje in the Idrija fault zone along the northern border f Hrušica (Fig. 2.4.5). .4.2.4. Nanos with Hrušica and Zagora and the northern border of tie Pivka basin In the series of the High Karst morphological units of western Slovenia; lanos Mt. takes a special place due to its wide ridge and background deep in Irušiea and Zagora. This speciality derives from its geological structure with lick beds of carbonate rocks, in particular Cretaceous and Jurassic limestones f the Hrušica nappe. On the southern side they are over-thrusted to the koto 3: Mt. Nanos above the village of Razdrto (Photo by P. Habič). Javornik-Snežnik thrust sheet; from the northern side they are underlain by Trnovo nappe and interjacent sliccs (PLACER 1981). In its structure and at the surface also a recumbent fold thrust over flysch is well seen; it is jagged by the Idrija and Predjama fault zones and also by interjacent faults and it is differently tcctonically displaced along them. From northern, western and southern side Nanos Mt. (Photo 3) is bounded by flysch with deeply downcut superficial flows. These streams have contributed to an important exposure of the more resistant carbonatc rocks and consequently to more abundant karstification. The High karst border of Nanos between Vipava and Pivka does not essentially differ from a similar one on Trnovski Gozd, but more important morphological differences appear in southern and eastern border. Nanos itself is about 12 km long and about 7 km wide, and forms together with Hrušica, the uninterrupted karst plateau between Vipavska Dohna and Hotenjsko Podolje of more than 15 km. Nanos is highest on the north-eastern side, where its peak Suhi Vrh reaches 1313 m. It is relatively high on the eastern side also; Debeli Hrib is 1209 m high and in-between is a sort of plain with cones and valleys between 1000 and 1100 m a.s.l. The distribution of cones, dry valleys and ouvalas in this part of Nanos is controlled by the structure of the rock basement and also by long-lasting karstification which is typical of the highest parts of Trnovski Gozd, Nanos and Hrušica. In this part there are most caves and shafts, among them Slapenski Ledenik and Strmadna (HABIČ 1963). Westwards Nanos lowers in relief steps to a margin ledge similar to the one met at Voglarska Planota and Otlica; this one on Nanos is also between 800 to 900 m. This ledge is cut by a precipitous edge above Vipavska Dolina; parallel to it two dry valleys developed, called Ravnik and Lipe. The last one is deepened in its NANOS NW SE Debeli hrib Slapenski ledenik Suhi vrh VIPAVA PraslovecORLOVŠE : V. Tržki ledenik Debeli vrti ; PIVKA Bpla LIPE RAVNIK I Strmadna UBELJSKO ŠEMBIJSKA BAJTA 1288 ''Ü® Fig. 2.4.6: Longitudinal section of the Nanos plateau. upper part by the elongated ouvala of Sembije; towards the north-west it remains hanging, as at Ravnik, above the semi-circular border between the Vipava and Bela valley near Vrhpolje. The ledges on this slope of Nanos are structurally controlled and partly associated with gradual downcutting of the Bela stream into flysch between Vipava and Col. The intensive entrenchment of the Bela valley was enabled by tectonic subsidence of Vipavska Dolina between Vipava and Ajdovščina. Near Vipava the flysch barrier at the foot of Nanos had been eroded below the present valley's bottom. The subsided part of the valley was partly filled up by Quaternary sediments which dammed the runoff of karst waters from Nanos and thus caused the delta-like distribution of the Vipava springs (Fig. 2.4.6). The flysch cover of Nanos extends in the western, southern and southeastern part from Vipava, where it is below 100 m, to the border below Pleša (1262 m) where it reaches near Razdrto the height of about 800 m and near Sv. Brie below Suhi Vrh 1000 m. Below the precipitous wall called Rjava Stena above Strane it lowers to about 800 m and still more in a direction towards Stranske Ponikve and further on towards Predjama. In this part a flysch base is relatively lower, concordantly to Hrušica in the east from the Predjama fault. Also the steep eastern slope of Nanos corresponds to tectonically relatively uplifted block. Thus Hrušica starts on the western side by Črnjavsko Podolje which is deepened at the foot of uplifted Nanos in the Predjama fault zone and remains hanging from a pass above the recent valley of the Bela near Podkraj towards Pivka basin. There the plain opens widely into a margin karst ledge called Podgora between Šmihel, Predjama and Studeno at the altitudes from 600 to 650 m. In fact it is a pediment shelf in the southern thrust edge of Hrušica. Above Predjama and Bukovje the steep slope of Hrušica reaches the altitudes slightly above 800 m, above Studeno and Strmica up to 1000 m. The higher eastern part belongs to tectonically uphfted Planinska Gora and Zagora which are separated from the lower Hrušica by a dry valley between Gorenje near Bukovje and Laniše near Kalce. To the south and east Zagora is bounded by a steep slope above Planinsko Polje and plain between Grčarevec and Kalce. Hrušica in a narrow sense of meaning is a sort of triangular inlier of karst surface between southern border of Trnovski Gozd and the northern part of the Pivka basin. To the east of Streliški Vrh (1265 m) and Javornik (1240 m) there is a karst ledge overlying the limestones of Hrušica nappe at about 1100 m; the next, lower, step surrounds Javornik from Nadrti above Hotenjsko Podolje to Podkraj above the Bela valley, about 900 m high. South from the road Kalce - Podkraj the lower, central, part of Hrušica continues along 150 m high slope in a south-west - north-east direction at altitudes from 800 to 900 m (Fig. 2.4.7). On the extreme southern border of Hrušica at the contact with flysch the Pivka basin is located. This part of the basin is an morphologically and H R U Š I C A Otavnik V. Rogač Medvejšek HRUŠICA Jama pod Gradom 663 Fig. 2.4.7: The morphographic section through the Hrušica plateau. hydrographically interesting area with small sinking flows, from the Stranske to Šmihelske Ponikve, Lokve, Ribnik, Mrzlek and Belščica, and also the Osojščica near Belska Žaga and five swallow-holes south of Studeno. Here lies the bifurcation watershed between the Vipava and the Pivka, between the Adriatic and the Black Sea. Blind valleys of sinking streams end with hmestone walls where active influent caves developed at several levels. The largest is Jama pod Predjamskim Gradom (HABE 1970) which consists of underground passages that even reach Vipavska Jama and karst springs of the Vipava on the other side of Nanos. 2.4.3. Geomorphological Processes and Development While reviewing the relief properties of single orographic units we noticed the differences in shape and development of surface that are supposedly due to differences in exogenic, climatic and hthologically controlled geomorphological processes in impermeable rocks with prevaihng fluvio-denudation transformation on one hand and on the other hand by karstification of limestones and dolomites. An essential difference between erosional dissection and lowering of the surface on impermeable rocks and in preservation of older rehef forms at the karstified surface was shown. During long-lasting geomorphological devel- opment from the Upper Tertiary onwards, the geological setting became more and more important but so also did the differentiated tectonic dynamics. An older, levelled surface had been partly covered by fluvial sediments and later exposed by gradual tectonic uplifting to more differentiated erosional and corrosional factors. Important changes occurred in the fluvial net and also in the direction of superficial waters. On one hand the previous river net disintegrated due to karstification, and on the other hand the superficial flows changed their directions due to tectonic uphfting or relative stagnation of single parts. All these processes occurred in the active geotectonic area between the Adriatic and Southern Alps. From the hydrographic point of view the biggest changes occurred at the Adriatic-Black Sea divide. From the climatic point of view the conditions at the passage between Submediterranean and Alpine continental climate were decisive. Climatic influences were particularly strong during the Pleistocene when warmer and cooler, more dry or more humid periods alternated. The traces of glaciation in the highest parts of Trnovski Gozd are preserved, and the Soča valley glacier reached down to confluence of the Soča and Idrijca. In cool periods a major part of the High Karst was exposed to typical periglacial processes. In that time also karstified limestones and dolomites suffered intensive mechanical weathering. This is evidenced by huge scree cones remaining, now covered by vegetation, at the foot of the karst border above Vipavska Dolina and also in headwater gulhes and gorges in the northern side of Trnovski Gozd. Periglacial and glacial debris had also been deposited in dohnes and ouvalas on the whole plateau, especially over the less resistant flat limestones. In thick-bedded limestones corrosional deepening of dolines and ouvalas prevailed, giving them a shape of larger gently sloping dolines. These features are more frequent at altitudes above 1200 m; in lower-lying areas karstification is better expressed in fractured and broken fault zones. These features are connected by several deep shafts but also caves where snow and ice now remain during the whole year. The considerable vertical permeability of the karst underground is due to karstification in cold periods when solution reached deeper than in warmer periods when corrosion was more intensive on the surface itself. The mostly bare rocky surface on the higher parts of Trnovski Gozd (Photo 4) shows the properties of high mountainous karst. Solution flutes and karren are in some places slightly changed and weathered, but some features remained that had already developed above the upper tree limit. In the cold period this hmit was at about 600 m a.s.l. and the limit of permanent glaciation reached somewhere to altitudes between 1250 to 1300 m. When the chmate warmed, chmatic and vegetation belts rose and the present-day tree limit is at about 1450 m which is relatively low yet it is controlled by the isolation and exposure of the highest parts of Trnovski Gozd. A large amount of precipitation contributes to the intensity of recent erosion and dissolution processes in particular, as it occurs mostly in the winter half of the year and Photo 4: Karren surface round Otlica (Trnovski Gozd) (Photo by P. Habič). during the frequent summer storms with heavy rain. Intensive karstification and modest soil cover on the hmestones enable the precipitation to drain underground quickly and feed abundant karst springs at the border of the High Karst. Geomorphological processes and karst and other geomorphologic features are studied in detail in geomorphologic and speleological treatises by MELIK (1959, 1963), RADINJA (1972), GAMS (1974), HABIČ (1968, 1974, 1992) and others. 2.5. SPELEOLOGICAL PROPERTIES OF THE AREA (A. MIHEVC) There are 489 caves known and registered on the area of Trnovski Gozd and Banjšice plateau. The longest cave is the Predjama cave, the 7571 m long ponor cave of Lokva stream. The deepest caves are Velika Ledena Jama v Paradani, Jazben, Habečkov Brezen and Strmadna on Nanos plateau. There are 17 caves longer than 200 m and 18 deeper than 100 m. The majority of the pothole entrances lies at 800 m a.s.l. where the average annual temperature is about 4° - 6° C. Frequently, the entrance parts of the potholes compared to the interior parts are widened. Numerous potholes are blocked by ice, snow or break-down blocks. The basic shapes of the potholes not yet spoiled by the superficial influence may be observed in inner avens only. The accessible caves are of different types: simple potholes or shafts of different depths systems of shafts and inclined or horizontal passages, ponor caves on the contact limestone with flysch or dolomite on the plateau and spring caves of different types on its foot. Most of the caves, about 70% are simple potholes and other smaller corrosive caverns formed by rain and snow waters. Most of caves are not very deep, 262 less than 20 m and only 7 are deeper than 200 m. Depth and number of caves more than 300 m 3 200 - 299 m 4 100 - 199 m 10 50 - 99 m 49 20 - 94 m 119 1 - 19 m 262 The following caves, briefly described, partly with a cave plan, are assumed as the important caves of the area under investigations: Vipavska jama Situated at the foot of Nanos at the springs of Vipava, the cave consists until recently of an artificial tunnel, which reached two natural cavities, so it acts as a spring during high discharge of the Vipava. Recently, through one of the cavities cavers entered in a about 1 km long maize of epiphreatic galleries developed along fractures. The survey is in progress but a plan doesn't exists yet. There are great discharges through some of the galleries, and water oscillates, according to sediments for about 25 m only 400 m inside the Nanos karst massif. Veliki Hubelj The cave entrance is in an altitude of 249 m, and forms the high water spring of the Hubelj river. The cave is 440 m long and is about 50 m above the permanent spring which is 219 m a.s.l. The cave is a maze of passages developed along joints and fractures in non bedded limestone. A cave plan is given in Fig. 2.15. VELIKI HUBELJ ETRANCE 249 m Fig. 2.15: Cave plan of the Veliki Hubelj. Ledenica na Dolu With an entrance in 995 m a.s.l., a length of 50 m and a depth of 80 m, this cave is developed in Jurassic limestones (Fig. 2.16). In the bottom part percolating water can be observed with a discharge up to 30 1/s after heavy rain. Its big entrance allows cooling of the cave during winter, but winter ice melts later in the year. 995 m LEDENICA NA DOLU 'm □ d/ /<3 n n D/ Ö ETRANCE Fig. 2.16: Cave plan of the Ledenica Na Dolu. Belo Brezno The entrance to this simple 40 m deep shaft is in an altitude of 1240 m. The cave consists of vertical shaft which is filled with rocks and snow in the depth of about 35 m (Fig. 2.17). Short narrow rift continues to depth of about 40 m, where further passage is blocked by gravel. The cave Belo Brezno was one of the main injection points for the tracing experiments carried out in the framework of the project (compare Chapter 6). BELO BREZNO o 1230 m A Fig. 2.17: Cave plan of the Belo Brezno, injection place for the repeated tracer injections in 1993, 1994, 1995 (see Chapter 6). Ledenica V Kozji steni LEDENICA V KOZJI STENI 1185 m Fig. 2.18: Cave plan of the Ledenica V Kozji Steni. Photo 5: Ice cave Ledenica V Kozji Steni (Photo by A. Mihevc). This ice cave in Kozja Stena is a 89 m deep pothole with a large permanent cave glacier and resembles regarding its shape and dimensions to a large collapse doline (Fig. 2.18, Photo 5). The entrance lies in an altitude of 1200 m. The 60 m deep entrance vertical drop having the dimensions at the top of 50 X 60 m, about 50 m deep the pothole narrows to 30 x 25 m. The bottom of the entrance pitch has a double depression leading downwards into common chamber where a large ice lake closes the cave continuation. The entrance pitch is developed in Jurassic limestone and dolomitic limestone in a strong fissure zone in N-S direction. By linkage of parallel potholes developed within this zone an ice volume of about 86.000 m-' can be assumed. Velika Ledena Jama V Paradani Velika Ledena Jama V Paradani (Great ice cave in Paradana) is the deepest and also one of the biggest ice caves of the whole karst plateau (Fig. 2.19). It consists of series of shafts, connected by short fossil or active meanders or collapsed rooms. The depth of its surveyed part is 385 m, but in August 1996 new parts were discovered. The cave is estimated to be about 700 m deep now, but no plan of newly discovered parts exist yet, as explorations are still in progress. The cave is developed in stratified Triassic limestone and dolomitic limestone. Entrance of the cave is situated in altitude 1100 m a. s. L, in the bottom of larger, 60 m deep closed depression. This enables cold air to descent and flow into the cave during the cold period of year, forming ice to depth of about 200 m. At the bottom, even in summer, temperature does not exceed + 3° C. The entrance part consists of three halls with permanent ice, it quantity estimated to 3000 m3 and was used as a natural source of ice. The volume of ice oscillates due to climatic changes and self controlling mechanism of filling in and reopening the narrowness at the entrance. This permits the cooling of the inner parts of the cave and so freezing the percolating water. Permanent ice is situated in the entrance part of the cave (Photo 6), in parallel shafts and in some chambers. This are three separated ice bodies, which are formed by freezing of percolated water in cooled cave. Ice level or better quantity is changing, records exist for last 25 years. In dry winters of the past years only little new ice was formed. The inner part of the cave consists of short galleries and shafts, all situated on a very small area of 150 x 150 m. There are 38 inner avens within the cave. The deepest is 240 m deep followed by 98, 55, 40 and 35 m deep avens, the others are smaller, all together about 2000 m, and thus they represent the main building element of the cave, which was formed by percolating water. Three morphological different types of shafts are evident in the cave: - shafts developed in steep meanders following the dip - shafts developed in fissured zones. They originate along vertical joints one 1135 m VELIKA LEDENA JAMA V PARADAMI 50m Fig. 2.19: Cave plan of the Velika Ledena Jama V Paradani. above another, or are parallel, formed along one or along parallel joints third type doesn't follow the structure. In parts, which are accessible they just drill their way down, having a stable point recharge and well drained bottom. Photo 6: The cave Velika Ledena Jama V Paradani (Photo by A. Mihevc). Ali three morphological types may also mean three different types of water percolation trough the vadose zone of karst. Jazben Entrance to cave Jazben is situated near Kanalski Vrh village in 574 m a.s.l. The cave is 334 m deep, formed near the contact of permeable upper Cretaceous limestone and flysch marls. The cave consists mostly of a series of shafts. Entrance part of a cave is dry, but in depth of about 120 m water appears. The cave than follows a NW - SE fault, along which it cascades to depth about 300 m. This part is developed in massive limestone. Below that point cave changes into a narrow meander which follows the dip of marly, thin bedded limestone with chert. Habečkov brezen The 336 m deep cave is developed near the contact of Triassic dolomite and Cretaceous limestone. It consist of series of potholes, which can be followed to a narrow rift at the bottom part and which terminates in a sump at elevation of 332 m. This sump is only 3,6 km apart from the springs of Divje Jezero at the Idrijca river. Divje Jezero spring Divje Jezero is a karst spring of Vauclusian type. The level of the lake in which the water flows is in altitude 320 m. The submerged gallery that supply it with water is explored to the depth of 122 m (Fig. 2.20). The first part of cave to depth about 95 m is steep and reaches with a lower angle the terminal depth. Beyond the gallery it still continues. DIVJE JEZERO -112m Fig. 2.20: Cave plan of the Divje Jezero. Slapenski ledenik Slapenski ledenik ice cave is located in the bottom of a small dohne in an altitude of 1010 m on the plateau of Nanos. Under the entrance, a 30 m deep shaft, a large room is developed, partly filled with ice and snow (Fig. 2.21). Both were used for water supply too. On the side of this chamber a second shaft reaches the lowest part of the cave at -112 m. During the tracing experiment in 1995 (compare chapter 6.) the tracer was injected in the first room at the depth of about 30 m in between boulders and the wall of the cave. SLAPENSKI LEDENIK 1010 m 0 10 20 30m 1-1-1-1 Fig. 2.21: Cave plan of the Slapenski Ledenik, injection place for the experiment in 1995 (see Chapter 6). Strmadna Strmadna cave is the deepest cave of the Nanos plateau. It entrance is in ahitude of 1060 m a.s.L, and it is 218 m deep. The cave is a system of shafts mostly controlled by fractures in direction NW - SE. 2.6. GEOLOGY AND HYDROGEOLOGY 2.6.1. Geological Description (j. čar) The geological description covers the territory hmited by the valleys of the Vipava, Soča, Idrijca, Trebuša, Belca and Zala rivers from the southwest, west and northeast, respectively. To the southeast the border of this territory runs along Hotenjsko podolje (Hotenja lowland) across Planinsko polje (Planina polje) through Postojnska Vrata (Postojna gate) and embraces the Pivka basin and Nanos (Mt. Nanos). The basic data on the geological conditions on Banjška Planota (Banjščica plateau), the Trnovski Gozd (Trnovo forest). Črni Vrh plateau, Hrušica, Pivka basin and Nanos can be found on the geological maps of Gorica (BUSER 1968), Postojna (BUSER et al. 1967) and Tolmin (BUSER 1987) and in the corresponding descriptive notes and legends. More details and particularities about the geological structure of the regions may also be found in the works of BUSER (1965), MLAKAR (1969), PLACER & ČAR (1974), PLACER (1981), ČAR & GOSPODARIČ (1988) AND JANEŽ & ČAR (1990). Reviews of geological discussions of older authors are also included in the listed works. Based on the above mentioned literature, the official maps and own mapping a general geological sketchmap of the investigation area is given in Fig. 2.22. Fig. 2.22: Geological sketchmap of Banjšice, Trnovski Gozd, Nanos and Hrušica: I - periglacial breccia and rubble, 2 - flysch rocks of the Upper Cretaceous, Palaeocene and Eocene age, 3 - Upper Cretaceous organogenic limestone, 4 - Lower Cretaceous bituminous limestone with inliers of dolomite, 5 - limestones and dolomites of the Jurassic age, 6 - Norian-Rhaetian limestone (Dachstein), 7 - Norian-Rhaetian dolomite, 8 - Carnian granular dolomite, alternation of silt and sandstone, 9 - normal geological boundary, 10 - erosion discordance, II - thrust line, 12 - fault, 13 - dip and strike of strata, 14 - dip and strike of inverse strata, 15 - karst spring. «i tß »a . Is /I ^ /s* 1 : 2.6.1.1. Lithostratigraphic Description Variously coloured Carboniferous (C) and Permian (P^^) clastic rocks, Upper Permian (P3) bituminous dolomites and limestones, Scythian (Tj) sandy dolomites, marlstones and silts with lenses of oolitic limestone, grey dolomite and marly limestones, crushable Anisian (T^') dolomites and variegated Ladin-ian (T^^) rocks represented by a dolomite-limestone conglomerate, lime sandstone varieties and pyroclastic rocks with intercalations of silicificated limestones can only be found in the upper part of the Zala torrential stream, which partly sinks directly into the basin of the springs of Podroteja. The comphcated mutual relationship of the above-mentioned rocks reflect the complexity of the entire overthrust structure in the Idrija region (MLAKAR 1969). The Upper Triassic Carnian (T,') layers are relatively modest in size in the region discussed. White, grainy non-bedded Cordevohan dolomite ('T,') is found in the Trebuša and Zala river valleys. The Julian-Tuvalian sandstones and siltstones and the dolomites with shale intercalations between layers build the steep slopes of the north side of the Trnovski Gozd above the Trebuša valley and smaller parts of the slopes on the right side of the Zala stream. The Upper Triassic Norian-Rhaetian "principal" dolomite is the first extensive lithostratigraphic bed in the region discussed. A broad band of this rock begins in the Idrijca valley south of Most na Soči, builds extensive terrains all the way to Čepovanski Dol (Čepovan valley) and extends to the northern periphery of the Trnovski Gozd. It builds slopes above Trebuša and Belca river valley, partially covers the Zadlog and Črni Vrh plateaux and the ridge extending to Javornik (1240 m). Norian-Rhaetian dolomite also builds the eastern slopes of Čaven (1185 m) and the southern side of Hrušica. In stratigraphically higher parts the grey layered dolomite passes into light grey layered oroganogenic Dachstein limestone. In the continuous belt it has developed between the Čepovanski Dol (Čepovan valley) and the central part of the Trnovski Gozd. It can also be found around Križna Gora (957 m) along the southeast periphery of Javornik. Norian-Rhaetian limestones and dolomites gradually pass into Jurassic rocks. On the Banjška Planota (Banjšica plateau), in the Trnovski Gozd, on Hrušica and on the eastern part of the Nanos range, all the Liassic (J,), Doggerian (J^) and Malmian (J^) lithostratigraphic units have developed, descending toward the southwest. The lithogical and according to fossils of the Lower and Middle Jurassic layers of the Trnovo Gozd is similar those of the old rocks of Nanos and Hrušica. Lithological changes of the Malmian layers are noticeable to the east of Col. The layers of Jurassic rocks with a thickness of 1000 to 1500 meters have primarily developed in the form of limestones and dolomites with all the characteristic mutual transitions. The variously coloured thick and oohtic limestones alternate and transform along the edges into white, grey or even brown-coloured dolomite. The Doggerian grey limestone with chert found at Banjšice and in the west part of the Trnovski Gozd is a particularity. In the entire region discussed, the Lower Cretaceous (K,) rocks were deposited in the form of characteristic carbonitic fades. However, significant lithological differences already appear in the development of Upper Cretaceous (Kj) rocks. The Cretaceous rocks are about 2500 to 3000 m thick. On the periphery of the Pivka basin, on Nanos, Hrušica and in the Trnovski Gozd the Lower Cretaceous rocks have developed in the form of brownish to light-grey limestone with intercalations of grained bituminous dolomites. These are followed by grey to orogenogenic Upper Cretaceous limestones rich in shell biostromes. The carbonate Cretaceous development ends with an erosion-al discordance. Palaeocene (Pc) and then Eocene (E,) flysch rocks are lying on the eroded Upper or Lower Cretaceous limestone on the western periphery of the region discussed, on Banjšice plateau south of the Avšček valley. Upper Cretaceous limestone breccia forms the base rock of the Palaeocene flysch on the plateau west of the Kajže spring. Even greater variations can be found in the region northeast of the Avšček valley. Here the Upper Cretaceous rocks appear in the characteristic flysch development forms and turbidite type of limestone of Voice (K^-^). These rocks lie above eroded Norian-Rhaetian, Jurassic or Cretaceous carbonates. Different types of limestone breccia with intercalations of greenish and reddish marlstone can be observed above the thin-layered limestone of Voice with chert, followed by brown marlstones and sandstones with intercalations of breccia (scagha, Palaeocene rocks are found in the west part of the Trnovski Gozd, at Banjšice and in the tectonic windows in the surroundings of Idrija. Typical lithological components are reddish, purple marlstones alternating with greyish red varieties and intercalations of marly hmestone. On eroded Upper Cretaceous hmestones near Idrija basal block hmestone conglomerates are covered with greenish-grey marlstones. In the surroundings of Grgar, at Banjšice and Kanalski Vrh, flysch rocks are deposited discordantly above the Upper and Lower Cretaceous rocks of various ages. At Lijak the Upper Cretaceous hmestones gradually pass into Palaeocene flysch rocks. Eocene flysch sediments are deposited discordantly on Upper Cretaceous limestones in the Pivka basin, in the belt between Črni Vrh, Col and the Vipava Valley and on the Vipava side of Nanos. In the vicinity of Lijak the transition from Palaeocene and Eocene rocks is gradual. The Eocene flysch consists of alternating brownish to greenish grey marlstones and quartz sandstones with intercalations of calcarenites and calci-rudites of varying particle range. Periglacial coarse-grained block breccia with reddish flowstone cement of the Quaternary age (Q) covers the flysch rocks on the south-western slopes of the Trnovski Gozd from Vipava on the west to the Soča Valley near Mrzlek. The breccias can also be found on the periphery of Nanos. The Holocene (al) is characterised by loams with chert found in some levelled parts of the Trnovski Gozd and extended unconsolidated slope debris from Col on the east to the Soča Valley on the west. 2.6.1.2. Tectonics The region discussed has a very complex tectonic structure (MLAKAR 1969; PLACER 1981). The predominant tectonic elements are the extensive and complex overthrusts which, in the past alpine tectonic phase, were cut with a dense system of subvertical faults. Thrust structure The overthrust structure is characterised by the repetition of Palaeocene-Eocene flysch in the overthrusted and underthrusted structural units near Gorica, in the Vipava Valley, Hruševje and in the Pivka basin. Vodice above Col and Idrija (PLACER, 1981). The above-mentioned alternation of poorly pervious flysch rocks and karstified limestones and the discordant and normally placed Palaeocene-Eocene and Cretaceous flysch on the west part of the Trnovski Gozd, Banjšice and Lom near Tolmin represent the basic structural hydrological element of the south-western part of Slovenia. The flysch of the Pivka basin as well as of the narrow flysch belt extending past the northern periphery of Nanos into the Vipava valley belongs to the Snežnik thrust sheet. Upper Triassic, Jurassic, Cretaceous, Palaeocene and Eocene rocks of the Hrušica nappe were thrust onto it. The Hrušica nappe encompasses Hrušica, Nanos and the central and northern part of the Vipava Valley to Gorica. Between the nappes at the west periphery of the Pivka basin, the Bukovnik, Debeli Vrh and Suhi Vrh interjacent shces are developed. These interjacent slices are comprised of the same rocks as Hrusica's nappe. In the Idrija region, the Hrušica overthrust unit is covered first with Lower and Upper Cretaceous limestone of the Koševnik interjacent slice, followed by a plate of Upper Triassic dolomite and Carnian rocks of the inversely positioned Čekovnik interjacent shce. These units have built the Belca river stream, the Zadlog-Črni Vrh plateau, the Hotenje lowland and part of Javornik, Križna Gora and the territory between Križna Gora and Col. The above-mentioned overthrusts and flysch rocks of the Hrušica nappe are covered by the Trnovo nappe, built of rocks from the Carboniferous to Eocene periods. It encompasses the entire Trnovski Gozd, Banjšice, Lokovec, Čepovanski Dol and the Trebuša valley. Strike-slip faults The region discussed is limited on tlie nortlieast side by a 300 to 1500 m wide fault zone of the Idrija fault. Within the broader fault area numerous accompanying faults are in progress, branching from the main fault plane and repeatedly joining it. The most important accompanying fault zone is the Zala fault. In the enclosed map of the Idrija fault zone it appears between Most na Soči and. Hotedrščica. A significant regional fault, which cuts across the entire region discussed, is the Avče fault, whose east past is also referred to as the Predjama fault. It extends from the Soča valley near Avče to the periphery of the Pivka basin. Between Idrija and the Avče fault an even greater number of significant tectonic zones can be observed in Banjščica and in the surroundings of Grgar. These faults undoubtedly cut across the central and southeast part of the Trnovski Gozd, but were not defined in detail by previous geological mappings. Running along the southwest side of the region discussed is the regional Rasa fault, which disappears below Lijak into the flysch rocks of the Vipava Valley. The Grgar valley on the northeast side of the Rasa fault is cut by several quite extensive fault zones. At present their continuation in the direction south-east is still not known. Tectonic lithological mapping on a scale of 1:5000 proves that the areas between the above-mentioned faults are interwoven with numerous crushed zones of varying width extending in the direction north-south, east-west or north-northwest, south-southeast. A similar structure can also be expected in Hrušica, Nanos, Pivka basin and its periphery. 2.6.2. Hydrogeology (J. JANEŽ) 2.6.2.1. The review of the previous investigation Underground water of Nanos, Trnovski Gozd and Banjšice is the subject of hydrologic and hydrogeologic investigations for about 40 years. P. HABIČ published the largest number of works and papers (HABIČ 1968, 1981, 1983, 1985, 1987.). The same researcher was the author of many waters tracing tests in the catchment area of Mrzlek, Podroteja in Hubelj. Underground water tracing investigations in Slovenia 1972-1975 (GOSPODARIČ & HABIČ 1976) confirm important water connections in the catchment area of Podroteja and Divje Jezero. PLACER & ČAR (1974) explained the regional hydrogeological position of the karst springs. ČAR & GOSPODARIČ (1988), JANEŽ (1990) and PETRIČ (1994) wrote about the Lijak boiling spring. JANEČ & ČAR (1990) defined the geology and the catchment area of the spring Kajža. 2.6.2.2. Hydrogeological Classification The surface of the Trnovski Gozd, Banjšice, Nanos and Hrušica covers about 700 kml That is 3.4 % of the total Slovenian territory respectively 7.8 % of the Slovenian karst surface. The total discharge of the karst springs in dry periods reaches more than 2 mVs (7 % of Slovenian karst underground water). During high water the main karst springs (Mrzlek, Lijak, Hubelj, Vipava, Podroteja, Divje Jezero, Kajža and Hotešk) drain about 280 mVs of water. The whole area can be divided according to the permeability of their lithological characteristics in several hydrogeological units (compare Fig. 2.23): - well permeable rocks - aquifer(s) with karst and fissure porosity - well permeable rocks with intergranular porosity - medium permeable rocks - aquifers with fissure porosity - impermeable rocks. The karst porosity aquifers are formed in Upper Triassic Dachstein hme-stone, Liassic, Dogger and Malm limestone, Lower and Upper Cretaceous limestone and Upper Cretaceous hme breccia. The main hydrogeologic units are the karst aquifer of Hrušica, the karst aquifer of Nanos, the karst aquifer of Črni Vrh plateau, the karst aquifer in the catchment area of Hubelj and the karst aquifer of the western part of Trnovski Gozd and Banjšice. In all these cases the existence of deep karst systems is in question. Well permeable rock with intergranular porosity are built by coarse grained to block shaped Quaternary periglacial breccias and unconsolidated Holocene slope debris. They cover big surface in form of an almost uninterrupted belt on the southern border of Trnovski Gozd and Nanos. The discharges of the slope debris springs yield up to 15 1/s. As relative hydrogeological barriers the fissure aquifers have to be assumed. Aquifers with fissure porosity are built by dolomite of different age. The biggest extent has the Upper Triassic dolomite. It borders the karst aquifer from the northern side and partly direct the underground water runoff. The discharges of the springs in the dolomites reach up to 10 1/s. Uncrushed Carboniferous clastic rocks, Medium Permian (Groden) siltstone and sandstone, pure tuff beds of Ladinian age (in Idrija region), Carnian clastic rocks (impermeable footwall of the Upper Triassic dolomite in the valley of the Trebušica river) and Palaeocene and Eocene flysch marl (in the Fig. 2.23: Hydrogeological sketchmap of Banjšice, Trnovski Gozd, Nanos and Hrušica: 1 - well permeable rocks and sediment, intergranular porosity; 2 - well permeable rocks, karst aquifer; 3 - medium permeable rocks, fissure porous aquifers; 4 - impermeable rocks, relative hanging hydrogeological barrier; 5 - impermeable rock, lateral and footwall hydrogeological barrier, 6 - karst spring. surrounding of Trnovski Gozd and Nanos) form the impermeable lithostrati-graphic horizons. But due to the fact that those series are characterised by an alternating hthological setting with smaller inliers of more permeable sediments, fissured or karst aquifers between the impermeable rocks are important (Lower Schythian marly shists with lenses of oolitic limestone; Ladinian piroclastites with beds of silicified limestone; the clastites of Carnian age with various limestone inliers; flysch rocks of Palaeocene and Eocene age with calcirudite and calcarenite lenses). The hydrogeological role of lithostratigraphic units is controlled not only by permeability but also by primary stratigraphic superposition, tectonic setting and neotectonic geomorphologic terrain development. The hydrogeological barriers (footwall and sideways), hanging hydrogeological wall and relative hydro-geological barrier are distinguished. To hanging hydrogeological barrier belongs the area between Banjsice and Idrijca river where flysch rocks are found on the karstified base. The hanging hydrogeological barrier is depending on lithological structure and thickness of flysch either locally vertically or horizontally permeable. Limestone, sandstone and breccias intercalated as lenses or beds in water tight flysch marlstone and quartz sandstone accumulate some water that reappears in feeble springs. 2.6.2.3. Karst Aquifer of Nanos and Hrušica Nanos karst plateau is a karst fissured aquifer bordered on three sides by impermeable Eocene flysch. On the north-eastern side it continues along the Predjama fault to the karst aquifer of Hrušica. The interpretation of the geological setting (PLACER 1981) infers that flysch below the carbonate nappe of Hrušica lies higher (level about 0 m a.s.l.) than the flysch below the limestone of Nanos (in the north-western part of Nanos even up to -1300 m). The underground water flows out across the lowest gap in the flysch border in the Vipava spring. The minimal discharge of Vipava springs yields 700 1/s, medium annual discharges are from 6 to 9 mVs, and the maximal about 7 mVs (HABIČ 1973). The catchment area is bigger than 150 km^ and comprises the entire massif of Nanos and substantial parts of flysch and limestone surface near Postojna. 2.6.2.4. Hydrogeologie Structure of Trnovski Gozd and Banjšice Plateau The result of the overthrust tectonic in older Tertiary and neotectonic fault displacement is the superposition of thrust sheets, nappes and smaller interjacent slices. Hydrogeological conditions of Trnovski Gozd and Banjšice depend on that geologic structure and hthology. The flysch of Vipava valley belongs, according to PLACER (1981), to several tectonic units. The southern side is a part of the Komen thrust sheet. The flysch on the northern side belongs comparable to Nanos and Hrušica, to the Hrušica nappe superposed to the Snežnik nappe near Postojna. The flysch of the Hrušica nappe represents the impermeable footwall for the karst aquifer of Trnovski Gozd and Banjšice as well as the impermeable southern and southwestern sideways barrier in the Vipava valley. On the East it is thinned out and exhibits a carbonatic development. Therefore it represents an only partially (locally) hydrogeological barrier. Flysch beds that are near Javornik on the 1000 m a.s.l. strike towards west. In tectonic windows near Idrija the flysch reappears on the surface at the altitude of about 300 m. Near Lijak the flysch was drilled at the altitude -16 m (ČAR & GOSPODARIČ 1988) while the boreholes at Prilesje did not reach the flysch at the depth of -220 m. The shape and the inchnation of the impermeable base essentially influence on the direction of runoff of the karst underground water. Upper Triassic, Jurassic and Cretaceous limestone rocks of the Trnovski Gozd and Banjšice belong to tectonic unit of Trnovo nappe and build the central part of the karst aquifer. The underground water lies extremely deep. Between Soča river and Lijak low waters are found at the Hill 77 m being fed by the water level of the accumulation lake on Soča (JANEŽ 1992). The underground water level is higher in the northern part of Banjšice (the Kajža spring 191 m a.s.l.; JANEŽ & ČAR 1990) and especially in the background of Hubelj (270 to 290 m a.s.l.; HABIČ 1985). The underground water of the karst aquifers of Nanos and Trnovski Gozd (the springs of the Vipava river, Hubelj, Lijak) appear on the surface at the lowest points of the impermeable flysch border (PLACER & ČAR 1974) or on the erosion basis (Mrzlek spring near the Soča river). The northern border of the karst aquifer is built by dolomite rocks of the Upper Triassic age outcropping along the valleys of Trebušica and Belca at the base of the impermeable Carnian clastic rocks. Upper Triassic dolomites are locally important aquifers with fissured porosity with spring yields of up to 10 1/s. Between Hrušica and Trnovo nappe there are near Idrija two tectonic and hydrogeologic units. The Koševnik interjacent slice lying on the Hrušica nappe, flysch is built by karstified limestones of the Cretaceous age forming the central catchment area of Podroteja and Divje Jezero. The Čekovnik interjacent slice is built by the Upper Triassic dolomite in the inverse position where the underground water in the fissured aquifer is under pressure. 2.6.2.5. Important Springs The Podroteja karst spring (329 m a.s.l.) (Photo 7) is situated on the confluence of the river Idrijca and its right tributary Zala. The famous lake Divje Jezero hes 500 m Southwest from Podroteja (330 m a.s.l.). In both Photo 7: Podroteja springs (Photo by A. Mihevc). springs the water flows on the surface out of dark bituminous thick bedded Lower Cretaceous hmestone. The Vauclusian spring Divje Jezero has a karst channel of exceptional shape where divers have reached the deepest point in Slovenia till now, 122 m of depth. In Podroteja the underground channels are more narrow and inaccessible. The Podroteja discharge oscillates among 0,2 to some mVs. During low water Divje Jezero does not flow over the rim although the siphon's depression is always filled. During the high water the runoff of Divje Jezero is more than 60 m^ per second. Hubelj spring emerges on the highest altitude of all springs on the southern border of Trnovski Gozd. With a spring outlet at 240 m in dry periods. At high water the water table rises up 40 m higher (Photo 8). During the drought 300 to 400 1/s of water flow out of karstified limestone, but the highest discharges reach more than 40 mVs. The Vipava springs emerges at the western foot of Nanos (Photos 9 - 11). The most abundant permanent springs are in the Vipava town, 98 m a.s.l. To the Northwest there are several periodical springs. The minimal discharge of Vipava springs yields 700 1/s, medium annual discharge is from 6 to 9 m7s, and the maximal about 70 mVs (HABIČ 1983). The catchment area is bigger than 150 km^ and comprises the entire massif of Nanos and substantial part of flysch surface near Postojna. Photo 8: High discharge of the spring Hubelj in November 1996 (Photo by P. Habič). Photo 9: Karst springs of Vipava - Za Gradom (Photo by P. Habič). Lijak, a periodical karst spring near Nova Gorica, represents a hydrological curiosity due to extremely high but short lasting discharges. The spring acts as flood overflow spring for karst underground water of Trnovski Gozd that otherwise flow north-westward to 6 km distant springs along Soča river. The limestone walls above Lijak are separated from the flysch of Vipava valley by a vertical fault. The boreholes near Lijak hitted the karst channels 90 m deep. Lijak resurgence is active seven to ten times per year. Its activity lasts from one to several days, the most up to 20 days. The biggest discharge measured since was 32,6 mVs. The low water level approaches to the Soča accumulation lake level (77 m a.s.L). The artificial changes of the water level in the accumulation lake have a clear response in the hmnigraphic records of the Lijak. The influences are noticeable during low and medium water tables while during higher waters the influence of precipitation is stronger (JANEŽ f990). The water supply of Nova Gorica is based on the karst water of the Mrzlek spring (Photo 12), emerging directly in the Soča valley. The water quantities flowing directly into the Soča river can not be directly measured. It was Photo 10: Karst springs of Vipava - Pod Skalco (Photo by P. Habič). Photo 11: Karst springs of Vipava - Pod Farovžem (Photo by P. Habič). % yW -t» Photo 12: Karst spring Mrzlek, mixing with the Soča river water is well visible (Photo by P Habič). estimated that their amount at low water is about 600 1/s and 40 mVs at high water (IIABIČ 1982), Since the construction of the hydropower station Solkan the pumps are flooded and superficial Soča water breaks into the water supply system. Kajža spring lies in the valley of Avšček brook at 191 m a.s.L. Water appears on the surface at the contact of Cretaceous limestone and 20 m wide belt of strongly crushed rocks of the Avče fault. The lowest discharge of the spring is 7 1/s, t raises up to 1,5 to 2 mVs after heavy rain falls (JANEŽ & ČAR 1990). Hotešk is a karst spring in the north-western part of Trnovo plateau along the Idrijca river. Water catchment area of the spring is built by Upper Cretaceous and Upper Triassic limestone. The discharge oscillates from 30 1/s at low water to 6 mVs at high water. Čepovan valley is limited from the Trebušica by a ridge built of dolomites of Upper Triassic age. Most of the underground water drains towards Trebušica, smaller part only reaches the resurgence in the Cepovan valley about 610 m a.s.l.. It seems that the underground water has through flown to the Trebuša side due to dried up "Cepovan river" and deepening of the Idrijca and Trebušica valleys. 2.6.3. Geological structure and hydrogeological position of the Hubelj spring (j. janež) First hydrological data about the Hubelj spring were published by PUTICK (1928). Much later the studies about this spring were presented by HABIC (1970, 1985, 1987). PLACER & ČAR (1974) explained the regional hydrogeological position of the Hubelj spring. 2.6.3.1. Extent and method of mapping LITHOLOGIC-TECTONIC MAP OF HUBELJ BACKGROUND Fig. 2.24 Lithologic-tectonic map of Hubelj background: 1 - slope rubble, collapse block, screes; 2 -coarse-grained to block-like limestone slope breccia, younger. Quaternary; 3 - slope breccia, older, Quaternary; 4 - marlstonc, siltstone and sandstone; flysch, Eocene; 5 -light brown limestone, usually grained, rarely thick, oolitic limestone, non-bedded, bedded to thick-bedded, Jurassic - Upper Lias and Dogger; 6 - pure grained dolomite, dolomitized oolitic limestone, bedded to thick-bedded or non-bedded - Jurassic - Upper Lias and Dogger; 7 - strong fault, visible and covered; 8 - weak fault, visible and covered; 9 - supposed fault; 10 -nappe border; 11 - lithological limit; 12 - dip and strike of inverse beds; 13 - dip and strike of normal beds; 14 - dip and strike of fault plane; 15 - fissure zone; 16 -broken zone; 17 - crushed zone; 18 - karst caves: A - Veliki Hubelj, B - Hubljeva Kuhinja, C - Otliška Jama; 19 - spring; 20 - surface water; 21 - cross-section. Slightly more than 2 km^ of the immediately background of the Hubelj spring was examined by a detailed geological mapping in 1994. The steep slope of the Trnovo plateau, including the edge of the plateau at the north-eastern side and the first outcrops of the Eocene flysch (impermeable edge of the karst aquifer) in the South and south-west were mapped (Fig. 2.24 and 2.25). The average incline of the terrain with numerous overhangs is over 45°. The altitude difference between the lowest (190 m) and the highest point (855 m) is 655 m. The method of mapping of all outcrops is used. The scale of the map is 1:5000. The terrain is uncovered and the weathering zone is thin, so the identification of the bedrock is not difficult. Conditions on the flysch beds are rather different. Diluvium and weathering sediment cover the solid rocks and the outcrops are very rare. Besides, a thick layer of slope sediments - the Quaternary slope breccia, collapse blocks, slope rubbles and recent still active screes - covers a large part of Mesozoic and Tertiary bedrock and complicates the geological interpretation. The objects of geological mapping were mainly the lithology of rocks, the character of the contact between different rock types and the tectonic conditions. The method of mapping and interpretation of the crushed zones character, introduced by PLACER (1982), was used. Further ČAR (1982) developed this method for geological mapping of karst. Crushed, broken and fissured zones can be distinguished on the base of the tectonic damage of the rock. CAR & GOSPODARIČ (1988), JANEŽ & ČAR (1990) and ČAR & JANEŽ (1992) tested the method successfully for the explanation of geological, structural and hydrogeological position of karst springs on the edge of the Trnovo plateau and in Julian Alps. ŠEBELA & ČAR (1991) use this method to explain the evolution of some typical karst objects. It can also be applied Fig. 2.25 Geological cross-sections near Hubelj. for definition of hydrogeological background and protecting areas of karst springs (JANEŽ 19^). Stratigraphic definition of the mapped lithologic units in respect to their age and position is based on the relevant Hterature (BUSER 1968, 1973). 2.6.3.2. Geological structure near the Hubelj spring The mapped area consists of Jurassic, Eocene and Quaternary rocks. The slope of the Trnovo plateau between Otliški Maj, Navrše, Sinji Vrh and Hubelj spring is mainly built by light brown limestone. The limestone is usually grained, rarely thick. On several places it changes continuously into oolitic limestone. The limestone on Otliški Maj, Navrše and Rob is mostly non-bedded with rarely notable beds. Lower, in the spring area of Hubelj, the limestone beds are 40 cm to 2 m thick, some of them even 10 m. The limestone is in several places dolomitized or reerystallized into a pure grained dolomite. Often, oolitic limestone changes into the oolitic dolomite. The transition from limestone to dolomite is progressive. Same as the limestone, the dolomite is bedded to thick-bedded or non-bedded. Following the basic geological map, sheet Gorica (BUSER 1968; 1973), the carbonate rocks above the Hubelj spring are defined as Upper Jurassic (Oxfordian and Lower Kimmeridgian, J,''^), but the beds are more likely of the Upper Lias and Dogger age (Jj^ - brown and grey oolitic hmestone, thick limestone, grained dolomite), due to their obvious lithological features. The Eocene (Ypresian and Lower Lutetian (E^^)) flysch in the Vipava valley consists of changeable beds of marlstone, siltstone and sandstone. The beds are 5 cm to 30 cm thick. Flysch on the mapped area has no inliers of limestone breccia and calcarenites. Slope breccia, collapse blocks, slope rubbles and recent still active screes present the Quaternary sediments. There are two types of breccia. The older breccia builds the overhang ridge and the flattened area south-eastern from the Hubelj spring. It is partly bedded, agglutinated and has greater share of rounded clasts. The younger breccia is more chaotic, coarse-grained and block like. The unconsolidated slope sediments, collapse blocks and slope rubbles are also of different age. The youngest are recent active screes, that can be found at the foot of the rocky overhangs of today still active tectonic zones. The most expressive tectonic deformations are the result of the young fault tectonic activity. The main tectonic line is according to the interpretation found of BUSER (1968) the obvious continuation or one of the legs of the regional Avče-Dol fault. South-west under the Otliški Maj on the altitude of 500 m the visible fault plane (45/90) confines the limestone massive. The screes and slope rubbles accumulate on the south-western side of this plane. First outcrops of flysch can be found at the distance of 120 m. On location Ključ, southern from the Otlica cave, the fault zone is 50 to 70 m wide. At this point it divides into two legs that encircle the lens like peak of Navrše (857 m). The south-western fault plane builds the wall of Rob and the northeastern leg represents 10 to 30 m wide broken zone. The valley southern from farm Zavrhovc was formed along this zone. The course of the second fault line in the Dinaric direction is above the Hubelj spring at the altitude about 405 m. It is narrower, less marked and mostly covered with slope rubbles. It is displayed with a characteristic morphological step and with disposition of the connecting faults and crushed zones, those are interrupted at this line. On the geological map (Fig. 2.24, and Fig. 2.25: geological cross sections) a supposed fault is drawn south-eastern from the springs of Hubelj. It is indicated by an outcrop of the tectonic breccia behind the abandoned army barracks near the Hubelj spring and by the geological and morphological conditions of the wider area. Between these described tectonic lines there are the connecting crushed zones in the direction northwest-southeast. Their intensity varies from open wide fissured zones to crushed and broken zones. The broken zones are narrow and we present then on the geological map only with a line of a fault plane. The beds of Jurassic limestone dip in general towards south-west. The dip angle changes between 30° and 60". An evidently different dip direction can be established only at the western edge of the limestone, western and northwestern above the Hubelj spring. In a narrow, up to 100 m wide belt at the contact between flysch and limestone, the dip direction turns towards south (strike 170" - 190") and the dip angle reaches 75". At the Hubelj spring the dip angle is a little lower (22° - 40") and the beds dip towards south. The character of the contact between the Mesozoic carbonate rocks of the Trnovo plateau and the flysch beds of the Vipava valley north-western from the mapped terrain is not problematic even though the contact is covered. This is undoubtedly a subvertical fault. But more unclear is the character of the contact between the carbonate rocks in the background of the Hubelj spring and the flysch beds south-western from the Avče-Dol fault on the section from Gosta Meja to the Hubelj spring, and also eastern from the Hubelj spring. On Gosta Meja location flysch undoubtedly lies under the thin layer of slope breccia at the altitude of 475 m, whereas near the Hubelj spring thus 235 m lower at the altitude of 240 m. The morphology of the terrain indicates, that towards east the upwarding of flysch is more gently. PLACER & ČAR (1974) described the structure as a depression, a synclinal bow of the Trnovo nappe thrust plane with the axis in the northeast-southwest direction. The change of a dip direction of the Jurassic beds from south-west to south and simultaneous rise of the dip angle at the contact with the flysch is also a proof for such explanation. The thrust character of the contact at the section between Gosta Meja and Hubelj spring is transformed with younger northwest-southeast and north-south oriented fault deformations. 2.6.3.3. Hydrogeological position of the Hubelj spring It can be seen from the structural characteristics, that the Hubelj spring lies in the bottom of the expressive, narrow and deep structural depression in the thrust plane of the Trnovo nappe. Springs are situated in about 70 m wide belt at the altitudes from 240 to 265 m. Water generally comes from the bedplanes, widened by corrosion. The highest springs are in the eastern part and the altitudes of springs constantly decrease towards west. Above the permanent springs there are two caves. The "Veliki Hubelj" cave has the entrance at the altitude 280 m. Eastern from the spring there is the "Hubljeva Kuhinja" cave, which is not explored enough yet. The "Veliki Hubelj" cave is a horizontal cave - a temporary spring at high water - with permanent water inside also during draughts. The hydrauhc gradient of the underground water behind the spring is very high (HABIC 1985). The reason for such position of the water level is according to HABIC (1970) the low permeability of the Jurassic limestone. PLACER & ČAR (1974) gave an additional interpretation on the basis of the flysch basement shape near the Hubelj spring. For the correct explanation also the influence of the neotectonic movements must be considered. The arrangement of the karst rooms and the position of the underground water indicate the neotectonic lifting of the block. The karst corrosion is slower than lifting and it is not able to fuse the underground flow. The opposite process was examined at the Lijak spring, which lies in the structural lowered block with the karst channel in the depth of 90 m (ČAR & GOSPODARIČ 1988). Naturally, there are no karst features formed above the spring Lijak because of the neotectonic lowering. In this case the term "immersed karst" has also the neotectonic meaning. Finally, the determination of the depth to the impermeable flysch basement of the karst aquifer would be very important for the final explanation of the hydrogeological structure of the Hubelj spring. 2.6.4. Geologic conditions and some hydrogeologic characteristics of the Vipava karst springs (J. JANEŽ, J. ČAR) 2.6.4.1. The aim and method of investigation The aim of the investigation was to explain the detailed geologic position of the Vipava karst springs. The same as in the case of the Hubelj spring we used the method of mapping of lithology and structural elements. The scale of mapping was 1:5000. The lithologic-tectonic map of the Vipava area is given in Fig. 2.26. ' m i.' a i' ž- d- a izi: 6 280(3$ ' 7 ^tmo 8 " ^g i sanfra 12 sl^« 13 15 / 16 ® J. Janež, J. čar, 1995 Orswß by A. A»r»ht Fig. 2.26: Geologic position of the Vipava springs. 1 - Slope rubble, scree; 2 -Alluvial deposit; 3 - Periglacial limestone breccia; 4 - Eocene flysch; 5 - Upper Cretaceous limestone; 6 - dip and strike of beds; 7 - inverse beds; 8 - erosion discordance; 9 - geologic boundary; 10 - fault; 11 - axis of an overturned fold; 12-fissure zone; 13 - broken zone; 14 - chrushed zone in flysch; 15 - the Vipava karst .springs; 16 - sinking of the surface water Vipava karst springs: 1 Pri Kapelici, 2 Pod Lipco, 3 Perhavčev Mlin, 4 Vipavska Jama, 5 Za Gradom, 6,7 Pod Farovžem, 9 Čmcova Jama, 10-13 periodical springs (number of springs according to P. Habič 1983). We adopt the stratigraphic data about the age and position of the mapped hthologic units from the older geologic maps (PLENIČAR 1970; BUSER 1973). 2.6.4.2. The review of previous investigation Nanos and the springs of the Vipava river have been the objects of geologic, geographic, geomorphologic, speleologic and hydrologic investigation for over than hundred years. We count more than 90 scientific papers and treatises, that touch directly or indirectly the hydrogeologic themes. Nanos belongs to the most investigated karst areas in Slovenia. Hydrogeologic investigations of Nanos started more than forty years ago. MICHLER (1952), SAVNIK (1955) and HABE (1963, 1970, 1976) carried out the tracing tests of the sinking streams in Pivka basin. Later, HABIČ (1987, 1989) estabhshed the connection of the Stržen sinking stream near Postojna with the Vipava springs and possible connection of these springs with the brook at Vodice village near Col. HABIČ investigated also the Vipava springs. He describes precisely the situation of the springs, hydrologic regime, physical, chemical and bacteriological properties of the water, the water catchment area, the threat to the karst groundwater and necessary protection measures (HABIC 1983). The water level of the springs in Vipava oscillates for 2 m, but the position of the periodical springs near Vrhpolje is 20 meters higher. The groundwater level in the background should be much higher. There are no other data about the permanent underground accumulation of Nanos. SAVNIK (1959) and HABIČ (1983) described the Vipava cave. 2.6.4.3. Geology and morphology at the Vipava springs and their hydrogeologic consequences Nanos is an overturned anticline. The anticline axe falls gently towards north-west. Nanos is structurally a part of the Hrušica nappe. On the northeast it borders the Predjama fault. (PLACER 1981, 1996). The western slope and the beh around Nanos from Sanabor and Vrhpolje to Vipava are built of limestone of Upper Cretaceous (Senonian) age (PLENICAR 1970; BUSER 1973). This limestone forms the nearest background for all the Vipava springs. The limestone beds are few decimetres to one meter or more thick, with partly massive occurrence. The colour of the rock is mostly light brownish or grey-brown, rarely grey, light grey or white. Grained limestone prevails over the thin grained or thick limestone. Mostly it is more or less bituminous. North-east from Vrhpolje in the direction to Sanabor the beds of Upper Cretaceous limestone dip towards north-west (290 - 320°). The strike ranges between 25 and 40°. Near Vrhpolje the beds dip 270 - 290° towards west and the strike of the beds is the same - mostly 30°. Southern from Vrhpolje the Upper Cretaceous limestone still dips towards west, but in town Vipava the beds start to turn towards south-west. In the northern part of the town the dip is 250 - 260°, near spring Pod Skalco 235 - 250°, and further towards Petriška Vas 235 - 240°. The strike angle ranges between 30 and 50° in the northern part of the town, 45 - 55° near spring Pod Skalco and increases to 60 - 70° in the direction of Petriška Vas. Further to south-east the dip of Senonian limestone does not change. All the way to Hvalen Breg it varies between 230 to 240°. The strike angle is about 80°, at some places also 85 - 90°. Of course, that is a sign for the nearness of the arch-bend of the Nanos anticline. In the upper part of the slope, on the location Plaz and Pri Topolih the beds strike 40 to 80° in the direction 230 - 250°. The limestone beds are thick. Also the inliers of thin bedded marl limestone can be found. On the contact with flysch we notice few decimetres of limestone conglomerate. According to Buser (1973) the flysch beds that lie on the Upper Cretaceous limestone belong to Eocene (Upper Cuisian and Lower Lutetian). If the stratigraphic definition is correct, then there must be an erosion discordance between both hthologic units. We do not notice any angle discordance. The strike and the dip of the flysch beds and the beds of Upper Cretaceous hmestone are the same. Flysch beds are typical for the distal type of turbidites. Few centimetres or decimetres thick beds of marl and fine-grained quartz sandstone alternate in the rock. The number and the thickness of the calcrudite and calcarenite beds rise towards south-west. On location Gradišče the Baum sequences 1 to 2.5 meters thick, can be found. It is a medial type of turbidites with clear A, B, D and E horizons, while the horizon of current lamination C appears rarely. North-eastern from Gradišče the flysch beds dip steeply towards south-west. The position of the beds is therefore normal. At Gradišče the beds are vertical, and south-east their position is inverse, dipping 50 to 80° towards north-east. The axis of the overturned anticline is therefore well defined. It crosses the Gradišče village and joins the faults that come from Vipava. In the short section among Vrhpolje and Zavetniki the Eocene flysch is covered with Quaternary hmestone slope breccia, that is typical for the southern slope of Trnovski Gozd. At Vrhpolje the flysch is covered with limestone rubble. Along the riverbed of Bela among Vrhpolje and Vipava flysch is covered with alluvial deposits, composed of clayey thick-grained limestone and flysch pebbles. In the western part of Nanos the slope rubble and scree cover very small areas. This shows the relative tectonic inactivity of the area. The morphology of the relief confirms this supposition. Among Vipava and Vrhpolje the western slope of Nanos is monotonous. It dips slowly toward west - with the strike angle that correspond with the strike angle of the Cretaceous limestone. Northeast from Vrhpolje the Bela brook forms a narrow and up to 50 meters deep gorge in the Upper Cretaceous limestone. fOO to 150 meters above the gorge, at the location Njivce, there are remains of an erosion terrace, probably an older stream of Bela. That stream had the same direction towards south-west as the recent one. In the gorge, the limestone is weekly damaged with some fault and fissured zones. The direction of the Bela brook is mainly defined with the dip and strike of the Upper Cretaceous limestone. The hmestone of the western part of Nanos has no signs of the superficial karstification, except of some shallow dolines in the initial phase of evolution. It seems, that the surface was covered with flysch in the nearest past. Several smaller depressions in relief of the western part of Nanos, which are probably the remains of old surface water streams, have the same or similar direction as the one at Njivce location. The most outstanding remains of an old surface stream at Stari Grad above the Vipava town have the transverse Dinaric direction from the north-east to south-west. The origin of the valley is not connected with transverse Dinaric tectonic zones, but with the dip of the limestone. The third "hanging dry valley" is at Pri Topolih location above the Poljšakova Vas. A little more crushed hmestone has been mapped south from Vrhpolje. In that part the Bela brook sinks. In Vipava town the limestone is again more compact. It has only some rare fissures that are later extended by corrosion. So, the springs Pod Farovžem and Za Gradom come out from the tectonic fissures, extended by corrosion. The springs Pri Kapelici, Pod Lipco and Perhavcev Mlin drain the karst water from the vertical joints. The limestone is tectonically modified into the crushed zone in the amphi-theatrical rocky indentation named Skalnica, above the spring Vipavska Jama. The direction of the indentation is from west to east or 10 to 20° towards south-east. Its south (south-west) margin, that is morphologically exposed as an 10 to 15 meters high wall, is a fault zone with elements 30/90. The northern border of the amphiteatre has also the direction west-east, just like less visible fissures in the limestone. Inside the amphitheatre of Skalnica the rock is deformed into the crushed zone and the dip and strike can be measured only at few places. The origin of the Skalnica amphitheatre can be induced by the tcctonic deformation of the hraestonc, but also by a strong underground water stream towards the springs. There is a small chatico. that the depression is only the result of the erosion of crushcd limestone, in tiiis case the same surface forms should come into existence also on places where there are no karst springs or karst groimdwater streams; but they mostly do not. Such morphologic forms are characteristic for the surroundings of karst springs. The groundwater probably could not form bigger karst objects, becausc in the crushed limestone the well permeable cave break down originate simultaneously. If the amphitheatre of Skalnica is induced by cave break down, this process is in the initial phase. This agrees with our earlier ascertainment, that the relief in the western part of Nanos is still young and that the limestone was in younger geologic past covered with flysch beds. In the geologic future the result of this corrosion-erosion process will be a greater and ripe morphologic depression with overhanging walls, similar to those one at Divje Jezero near Idrija or Lijak spring near Nova Gorica. A stronger and 150 meters wide zone of Dinaric oriented faults crosses Poljšakova Vas. It seems that the strongest is the most north-eastern fault (50/ 80) with 50 meters wide broken zone. Parallel to the other fault planes a dense system of fissures can be found. Flysch beds in this fault zone are strongly folded. Considering secondary tectonic deformation we suppose another Dinaric oriented fault, crossing Hvalen Breg, Zgavska Vas and Gradišče. It should be mapped easier in the limestone slope of Nanos, south-east from the investigated area. 2.6.4.4. Some hydrologic data At the entrance in the gorge under Sanabor the discharge of Bela brook was in December 1994 and in January 1995 among 70 and 100 1/s. We estimate, that in the gorge all the way to Vrhpolje the Bela brook does not sink. Obviously it sinks in the Vrhpolje village. At the end of the village the discharge was only 2 1/s and 500 metres lower the brook was dry. The viUage Vrhpolje strongly pollutes the karst water, but probably only the most northern permanent spring Crnceva Jama. Among Petriška Vas and Hvalen Breg there are some wegk but captured springs. Those springs drain groundwater from calcarenite layer; in flysch. 2.7. WATER QUALITY 2.7.1. Long-term Quality Monitoring (m. zupan) 2.7.1.1. Introduction Long-term water quality monitoring of the springs in Slovenia has been run since 1990. Already the first results of some main springs at the foot of the Trnovo plateau reminded that some pollution sources in the catchment area exist. In the frame of the present project the monitoring program in the springs was more extensive in years 1993-96. 2.7.1.2. Sampling And Chemical Analyses Program The samples for the water quality observations in the following sampling points were taken in 1993-1996: The Vipava spring 15 times for basic physical, chemical and bacteriological analysis and 6 times for the analysis of heavy metals and organic micropollutants in water and sediments and saprobiological analysis The Hubelj spring 15 times for basic physical, chemical and bacteriological analysis and 6 times for the analysis of heavy metals and organic micropollutants water and sediments and saprobiological analysis The Lijak spring 1 time for basic physical, chemical (including heavy metals and organic micropollutants in water) and bacteriological analysis in 1993; later the sampling was impossible because the borehole was stopped The Mrzlek spring 3 times for basic physical, chemical (including heavy metals and organic micropollutants in water) and bacteriological analysis The Podroteja spring 14 times for basic physical, chemical and bacteriological analysis and 6 times for the analysis of heavy metals and organic micropollutants in water and sediment and saprobiological analysis. In the catchment area two water supply captures in Čepovan (Čepovan and Čepovan Puštale) were sampled and analysed once in 1993; physical, chemical (including heavy metals and organic micropollutants in water and sediment) and bacteriological analysis The investigation program was run conforming to the methodology recommended by international organisations. 2.7.1.3. Analytical Methods And Water Quality Standards Sampling was done in various seasons of the year, preferably at low to mean low discharges. Samples for all types of analyses at one location were taken simultaneously. Samples were taken at a depth of 0.5 m and as close to the spring outlet as possible. In waters less than 1 m deep, samples were taken at mid depth. When sampling, air and water temperature, as well pH value, conductivity, free carbon dioxide and dissolved oxygen were measured. Samples for determining nitrite, chemical oxygen demand (COD), colour, and phosphates were conserved, samples for determining detergents, phenols, mineral oils, and formaldehyde were cooled. Basic physical and chemical analyses: In unfiltered, mixed samples, suspended solids, chemical oxygen demand (COD), biochemical oxygen demand (BOD), phenols, and detergents were determined. The unfiltered, sedimented sample was used to determine ammonium and nitrite ion, real colour, mineral oils, formaldehyde and ligninsulpho-nates. Other analyses were performed on samples filtered in Filtrak 388. Samples are analysed in the shortest possible time according to the following standard analysing methods for determining the basic water-pollution parameters (3, 4, 5): determination of free carbonic acid: titration with NaOH determination of dissolved oxygen: titration acc. to Winkler and measuring by an WTW probe determination of COD: K^Crp^ and KMnO^ determination of Ca and Mg ions: titration with NaEDTA nitrate ions: Na - salicylate procedure nitrite ions: procedure with sulfanilic acid solution iron ions: procedure with 1,10 - phenanthroline SiO^: procedure with ammonium molybdate solution aluminium: procedure with alizarin actual colour: comparison with K^PtCl^ standards anionic surfactants in detergents: methylene-blue method phenols: procedure with 4-aminoantipyrine ammonium ions: procedure with Nessler reagent phosphate ions: procedure with ammonium molybdate solution sodium and potassium: sulphate ions: formaldehyde: mineral oils: ligninsulphonates: flame AAS titration by thorin (6) procedure with phenilhydrazine hydrochloride (7) fluorescence measurement in hexan-extract (8) fluorescence method (9) Analyses of heavy metals and organic compounds Samphng of water, suspended solids, and sediments for analyses of metals and organic compounds (organic micropollutants) was performed according to the sampling methods as stated by DIN 38402-T15 and ISO 5667-T6. Concentrations of individual elements were measured by analytical procedures according to the standards stated in Tabic 2.10. The following organic compounds were analysed in unfiltered water by the method of gas chromatography: phenols, pesticides, polycychc aromatic hydro- lab. 2.10: Analytical methods to determine the content of metals in water, suspended solids, and river sediment. METAL WATER SEDIMENTS AND SUSPENDED SOLIDS Regulation Method Regulation Method Copper DIN38406-T7 F AAS DIN 38406-T7 F AAS Chromium DIN38406-T10 ET AAS DIN38406-T10 F AAS Nickel DIN38406-T21 F AAS DIN 38406-T21 F AAS Zinc DIN38406-T21 F AAS DIN 38406-T21 F AAS Lead DIN38406-T21 ET AAS DIN 38406X21 F AAS Cadmium DIN 38406-T19 ET AAS DIN 38406 T19 F AAS Mercury DIN 38406-T12 CVAAS DIN 38406 T12 CVAAS Notes: F AAS Atomic absoiption spectrophotometric analysis, flame AAS, instrument PE 1 lOOB ET AAS Atomic absorption spectrophotometric analysis, electrothermical AAS, instrument Zeeman 3030 CV AAS Atomic absoiptional spectrophotonietrical analysis, cold vapour AAS, instrument PE 2380 MHS 20 Tab. 2.11: Analytical methods to determine the content of organic compounds in water. Regulation Method Pesticides EPA 60S, 1982 and DIN 38407-T6 and T14 GC/MS/SIM Phenols EPA 604 and ref. 21 GC/MS/SIM PAG EPA 610 GC/MS/SIM PCB EPA 608, modified GC/ECD AOX DIN 38409-Tl 4 Stroehlein Coulomet 702 GL EOX DIN 38414-T17 Stroehlein Coulomet 702 GL carbons, (PAH) and polychlorinated biphenyles (PCB). Also the adsorbed organohalogen compounds (AOX) were analysed and GC/MS screening was performed (identification of untargeted organic compounds). Analytical methods for determining concentrations of organic compounds in water are given in Table 2.11. PCB was determined in the untreated sample of the sediment too. A GC/ MS screening was made from the extract of the sediment to identify untargeted organic compounds. As well halogenated extracted organic compounds (EOX) were analysed. Saprobiological and bacteriological analyses For the evaluation of the quality of surface waters from the biological point of view we used the saprobic system (10 - 15) and the calculation of the value of the saprobic index of a biocoenosis (16, 17). The value of the saprobic index (SI) increases with the deterioration of the living conditions from 1 to 4. Samples were taken biannually, in the cold and in the warm season of the year at lower discharges. The biological material was sampled in the littoral of the effluent down to a depth of ca. 0.5 m, where the sampling was not hampered by either water depth or speed. Semiquantitative and qualitative samples of periphyton and macrozoobenthos were taken. Macrozoobenthos was collected in the gravel to a depth of down to 15 cm in the ground semiquantitatively by means of a standard manual net (ISO 7828(E), 1985) with 0.5 x 0.5 mm mesh. With regard to the value of the saprobic index, the river is at a particular sampling point ranged into the corresponding quality class according to the values stated in Table 2.12. The bacteriological conditions of surface waters are subject to change due to the nature of the rivers, therefore the results of bacteriological analyses reflect the current state, i.e. pollution. Samples for bacteriological analyses were taken simultaneously with the samples for physicochemical analyses to be analysed according to the standard methods (4). The most probable number of Tab. 2.12: Quality classes according to the value of saprobic index. Trophic degree SI value Quality class Description of the quality of the water body oligosaprobic 1.0-1.5 1 uncharged to very little charged oligo to beta 1.51-1.8 1-2 little charged betamezosaprobic 1.81-2.3 2 moderately charged beta to aifa 2.31-2.7 2-3 critically charged alfemezosaprobic 2.71-3.2 3 heavily polluted alfa to poly 3.21-3.5 3-4 very heavily polluted polysaprobic 3.51-4.0 4 excessively polluted bacteria (MPN/1) was determined and the following more important groups of bacteria were qualitatively determined as well: faecal coliforms, faecal streptococci, Proteus sp., Pseudomonas aeruginosa, sulphite-reducing Clostridia and total number of aerobic mesophilic bacteria. Standards and guidelines for water quality assessment In general the Slovenian regulation classifies running waters with regard to their potential utilisation into four quality classes: • 1®' class: waters which in their natural state or following disinfection may be used as drinking-water, in food-processing industry, as well as in breeding high-class fish species (Salmonidae); • 2"'' class: waters which in their natural state may be used for bathing, water sports, breeding other species of fish (Ciprinidae), or following normal treatment (coagulation, filtration and disinfection), may be used as drinking-water or in food-processing industry; • class: waters which may be used in irrigation, or, following normal treatment, in industry, except in food-processing industry; • class: waters which may be used for any purpose only following an adequate treatment. The criteria used in ranging spring water courses into quality classes according to the contents of metals in water and suspended solids are shown in Table 2.13. Concentrations in bold type in the table make up the division between and quality class. Table 2.13. lists criteria for categorising watercourses into quality classes according to the content of metals in sediments. The criteria are based on natural contents of metals in carbonate sediment rocks (18, 19), amended with the results of investigation of certain surface waters in Slovenia at their springs or in polluted sections. Values in bold indicate the division between natural Tab. 2.13: Standards and guide-lines for classification of watercourses into quality classes according to the contents of metals in water and suspended solids. Meta! Hg/l Classification into quality classes 1. 2. 3. 4. Cooper <30 100 140 >140 Chromium <45 150 800 >800 Nickel <15 50 140 >140 Zinc <50 200 1400 >1400 Lead <15 50 140 >140 Cadmium <1.5 5 15 >15 Mercury <0.5 1 1.4 >1.4 Tab. 2.14: Standards and guide-lines for classification of watercourses into quality classes according to the contents of metals in river sediment Metal Hg/1 Classilicatiou into quality classes 1. 2. 3. 4. Copper <50 50-100 100-340 >340 Chromium <75 75 -150 150-540 >540 Nickel <50 50 - 100 100 - 360 >360 Zinc <650 650 -1300 1300-4600 >4600 Lead <80 80 - 120 120- 1000 > 1000 Cadmium <6 6-12 12-40 >40 Mercury <0.1 0.1 - 0.2 0.2-1 > 1 values and pollution. Table 2.14 lists criteria for categorising into 1.-2. quality class according to the content of organic micropollutants considering EC (20,21) and WHO (22) recommendations. The AOX and EOX are used as group criteria for monitoring the pollution with chlorinated organic compounds. The value of 0.5 - 2.5 jxg EOX/kg air dried sample represents the natural background, a concentration from 30 - 700 /j.g EOX/kg might cause the extermination of some benthos organisms (23). The identification of organic compounds in the GC/MS screening of samples of waters and sediments shows which organic compounds are present in watercourses and makes it possible to determine the pollution caused by man. In performing and evaluating the analyses less stress is lain on the quantity. Based on GC/MS screening, watercourses were evaluated according to the following criteria (Tab. 2.15): Tab. 2.15: Considered standards for classification of watercourses into the first(l.) and the second (2.) quality class according to the contents of organic micropollutants. ORGANIC COMPOUND 1.-2. QUALITY CLASS AOX - ng Cl/1 <5 Mineral oils - mg/1 0.01 Polychlorinated biphenyles - ng/I 0.1 Phenols - ng/1 0.001 Polycyclic aromatic hydrocarbons - ng/1 0.2 Pesticides - individual - ng/1. <0.1 Pesticides - total - ng/1 <0.5 quality class: the water shows presence of compounds of natural origin only 2"'' quality class: the water shows presence of compounds which are biodegradable and may be removed from the water with simple methods used in preparation of drinking water 3"' quality class: the water shows presence of not easily destructible com-povinds, which when infiltrating into the groundwater remain almost unchanged or are transformed into stable metabolites 4"' quality class: the water shows presence of chlorinated compounds which are typical man-caused pollutants, compounds which tend to accumulate in living beings and compounds with carcinogenic and/or mutagenic potential. 2.7.1.4. Results and water quality assessment The pollution of the water springs, in particular of the water, was relatively slight. The chemical parameters in most water samples did not exceed the normative for drinking water. On the other hand relatively high concentrations of mercury, cadmium, lead and copper in sediment samples were measured, which means that the pollution was nevertheless present in the investigated springs (Fig. 2.27.). The phenolic compounds and polycyclic aromatic hydrocarbons (PAH) were very often present in water samples of the Vipava, Hubelj and Podroteja springs (Fig. 2.28). The number of present PAHs determined in GC/MS screening was very high in water and sediments extracts. In the all investigated springs numerous compounds which originate from different human activities, were determined in GC/MS screening of water and sediment as well. 0,012- 0,01^ / , 0,008- 1 0,006- 0,004- rM 0,002- 0 mz 1993 1994 1994 1995 1995 Fig. 2.28: Polycyclic aromatic hydrocarbons and phenolic compounds in the water samples of the investigated springs (maximal values). 1993 1994 1993 »96 1933 1994 1996 1993 1994 199S Podrotoja 1993 ISM 1993 «9« tsss Fig. 2.27: Heavy metal levels (maximal values) in the sediment samples of the investigated springs. Tab. 2.16: Content of heavy metals in the sediments of the two water springs in Cepovan. Water spring Copper Zinc Cadmium Chromium Nickel Lead Mercury mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg Čepovan 58 583 4.4 81 61 <10 <0.05 Čepovan — Pultale 56 1600 6.5 37 43 228 <0.05 Tab. 2.17: Content of phtalic acid esters (sum) in the investigated springs. S« 1993 im of phtalic acid esters - 1994 g/1 1995 Čepovan 0.065 - - Vipava 0.120 0.115 0.520 Hubelj 0.126 0.200 0.360 Mrzlek 0.175 0.234 0.420 Lijak 0.145 - - Podroteja 0.260 0.615 1.110 In the catchment area we analysed two springs in Čepovan, which were polluted by polycyclic aromatic hydrocarbons in water (0.009 pig/l) and sediment. The concentrations of single PAH-s were not high but they were present in great number, thirteen in each Cepovan spring. We determined high contents of heavy metals in the sediment as well (Tab. 2.16). Phtalic acid esters were determined once a year and were found in all analysed water samples. Besides we estabhsh a trend of increasing concentration (Table 2.17). The presence of heavy metals and many different organic compounds in water and sediment samples is pointing to a constant pollution from the hinterlands. For the estimation of the water quality in the investigated springs all in the chapter 2.7.1.2 mentioned criteria have been taken into account and the results are shown in the Table 2.18. ■c »i Uk S'sf ž B. s a O p ? o 18 ^ ooooo+oooo § ^-isssgssss ^ a; Tab. 2.18: Evaluation of the quality of the investigated karstic springs in 1993-1995. 2.7.1.5. Contour diagrams of fluorescence intensity We used the excitation-emission matrix (EEM) method as pattern recognition technique and as semi-quantitative technique to follow the transport of natural and anthropogenic pollution in hydrologic system (WOLFBEISS 1993). We scanned the 3D spectra in all background samples. Emission spectra (300 nm to 550 nm, 5 nm intervals) were scanned over the range of excitation wavelengths (300 nm to 500 nm, 5 nm intervals) on the Hitachi-4500 fluorescence spectrophotometer. Slit widths for both excitation and emission mono-chromators were set at 10 nm. The comparison with the unchlorinated tap water shows that in all measured samples different organic compounds of unknown origin are present. Namely, we did not have the standards for this compounds and the determination of present compounds will be task for some investigation in the future. 2.7.1.6. Conclusions The chemical analyses of sediment in the Hubelj, Vipava and Podroteja springs have shown that pollution from the hinterlands is present and that water quality may suffer an abrupt deterioration. The results of microbiological analyses have been shown periodical pollution in the Podroteja, Hubelj and Vipava springs as well. Investigations of water quality should be followed by appropriate actions. Actions to protect water quality wherever it is still satisfactory and rehabilitation actions where appropriate. 2.7.2. Agricultural threats to pollution of water of TYnovsko-Banjska Planota (B. MATIČIČ) 2.7.2.1. Introduction The objective has been to determine the relationship between the soil water balance and mineral balance in the Karst region of Trnovsko-Banjška Planota in western part of Slovenia above Vipava valley and to find out if the possible excessive use of fertiliser and/or high intensity of animal husbandry in upland catchment area on Trnovsko-Banjška Planota could affect the quality of drinking water down in Vipava valley. The altitude of Trnovsko-Banjška Planota is about 800 m. In this region mainly shallow soil types (with depth of 10-50 cm) on limestone are found with low water holding capacity (22-142 mm) and high rate of infiltration. The amount of precipitation in Trnovsko-Banjška Planota is very high. The average annual value (1951-1980) in meteorological station Othca was 2457 Trnovsko Banj$ka planota, 1994 decade Fig. 2.29: The comparison between evapotranspimtion (calculated ETP) and precipitation in the Trnovsko-Banjška Planota for the precipitation station Otlica in the observation year 1994. mm. The extreme wet year was 1965 with 3233 mm of rain while the extreme dry year was 1973 with 1833 mm of rain (Source: Klimatografija Slovenije, Padavine, HMZ 1989). The amount of precipitation in 1994 (the year of our evaluation of water and mineral balance) was 1822 mm (from Jan.-Nov.); the evapotranspiration in this period was 628 mm (used modified Penman's equation - by DOOREN-BOS). The evapotranspiration according to this evaluation represents only 40 % of the amount of precipitation (Fig. 2.29). During the period of intensive precipitation, therefore, the processes of leaching of fertilisers can occur. It has been decided to evaluate regional and farm mineral balance for hilly karstic region of Trnovsko-Banjška Planota in order to identify vulnerability related to the nitrate problems in this less intensive agricultural region. 2.7.2.2. Groundwater and surface waters The pollution of groundwater and surface waters by nitrates, nitrites, phosphorus and amonium was monitored for the last four years (1991-1994, data base: 'State monitoring of waters'). Nitrate tn ground water - west Stovenia Aastria R7 iSOUENJSKO R8 SIRŽS UU6UAN8KO R» ZaORNJESORSNJSKO RIO NOTRANJSKO R11 SORIŠKO R12 OBAiNO-KRASKO • Hiinpltng point Fig. 2.31: Nitrate in groundwater of west Slovenia: average annual values and extremes. Nitrate ra rivers - west Slovenia ■15 - 12 f « 3 0 ■mm tas2 isea ism RII-aORlöKO IS C« im i«ü 1» 1SW aCMENJSKO is-i- tiu4 «•1 um KM fiS -Mite UUBUM8K0 Austria R7 DOLENJSKO RS ŠIRSE UUSUANSKO Re 200RNJE GORSNJSKO RIO NOTRANJSKO R11 GORIŠKO R12 OBALNO-KRASKO 0 fampHng point Italy Croatia w i' f • 18» 1t82 1*» MM Ria-OMUiO-iawfeto 1 1«- 512- II 1 f « f • A ^ ^ X » ^ ill ^ ^ a- ■ ■ ■ 0 1«*! 1«« 1MI ISN nio-mTMumo « lit! lae iw MM R7.00U»t.»K0 Fig. 2.30: Nitrate in the rivers grouped according to the region in west Slovenia: average annual values and extremes. Nitrate in groundwater (1991-1994) for western part of Slovenia, where karst prevails, is presented on Figure 2.31. Average annual values for nitrate concentration (in mg/1) in the region of Gorica was 39,08 in 1991 (maximal value: 51,36 mg/I), 51,70 in 1992 (maximal value: 76,61 mg/1), 43,84 in 1993 (maximal value: 69,08 mg/1) and 44,06 in 1994 when the maximal value of NO, was 67,97 mg/1. (The average ammonium concentration in mg/1 in this region was 0,01-1991, 0,02-1992, 0,04-1993, 0,02-1994. The average NO, concentration was 0,02-1991, 0,01-1992, 0,01-1993 and 0,01-1994. The average' P,05 concentration was 0,07-1991, 0,06-1992 no data for 1993 and 1994). Nitrate in rivers for this region is presented on Figure 2.30. The average concentration of NO, in mg/1 varied between 3,28 and 3,81 (maximal value was observed in 1992 being 7,53 mg/I). 2.7.2.3. Nitrogen balance at regional and farm level For mineral balance the main agricultural crops that occupy 92 % of arable land have been taken into evaluation. Nitrogen, phosphate and potash supply was calculated by the number of livestocks in the region and at each farm and the nitrogen, phosphate and potash content of liquid manure as well as the statistical data on trade of mineral fertilisers were taken into evaluation. Two nitrogen balances have been evaluated: GROSS-BALANCE taking into consideration nitrogen input from mineral fertiliser and animal wastes, minus nitrogen uptake by harvested crops (as being output). NET-BALANCE taking into consideration mineral fertiliser, animal wastes and deposition from the atmosphere as input and nitrogen uptake by harvested crops and ammonia losses to the atmosphere as output. The evaluation has been done using normative approach and methodology that has been used in EU countries. Agriculture on Trnovsko-Banjška plateau is extensive, animal husbandry is prevailing. Landuse, yields, use of mineral fertilisers and livestock population on selected farms is presented in Tables 2.19 and 2.20. Surface mineral balance was evaluated for 534 ha of arable land in region Dol-Otlica on Trnovsko-Banjška Planota, for 16.145 ha of arable land in Ajdovščina community (Dol-Othca is part of Ajdovščina community). Nitrogen balance on farm level (for 16 farms on Trnovsko-Banjška Planota) was evaluated for detecting possible point polluters in this region. 2.1.lA. Nitrogen surpluses as possible source of water pollution Average net-balance nitrogen surplus for Slovenia is about 56 kg N/ha. Higher values that can be considered vulnerable for the pollution of groundwater and surface waters can be found in regions with high intensity of animal husbandry in eastern part of Slovenia. Average low nitrogen surpluses on regional level are found in Western part of Slovenia where less intensive agriculture prevails. Average net-balance nitrogen surplus for Ajdovščina and Dol-Otlica on regional level was 36 kg N/ha; this value can not be considered as possible non-point source of pollution of groundwater and surface waters. Livestock density in Dol-Otlica is 0,81 LU/ha (Livestock unit per ha). The high nitrogen surpluses can be caused by higher animal production. In Dol-Otlica the average yields and uptake by crops are low; stocking rate over 2,1 LU/ha can cause net-balance surplus over 100 kg/ha what can be considered vulnerable for groundwater and surface waters (Tab. 2.19 and 2.20). The average nitrogen net-balance surplus on selected farms has been 36 kg N/ha and is varying between 13 and 87 kg N/ha (Fig. 2.32 and 2.33). On average nitrogen input from mineral fertiliser was observed very low - 11 kg/ha, while nitrogen input from organic manure was 72 kg/ha (Tab. 2.21). Livestock density in selected farms was between 0,4 to 2 LU/ha. The average phosphate surplus was found 27 kg/ha and the average potash surplus was 57 kg/ha (Tab. 2.22 and Fig. 2.34 and 2.35). Tab. 2.19: Structure of livestock on farms in the karst region, Slovenia, 1994. livestock % of total livestocjt LU/ha Region units Cattle Pigs Ponltry Sheep Other UAA kg N/ha kgP/ha l^K/ha SLOVENIA 1991 748836 58.4 16.6 22.7 0.4 1.9 1.26 89.82 50.80 92.0S SLOVENIA 1994 649916 62.6 16.0 19.6 03 1.6 1.10 77.51 42.34 76.47 farm 7 12.3 84.8 4.9 0.5 9.8 0.94 66.18 28.96 82.88 farm 13 11.1 93.7 5.4 0.9 1.05 74.91 33.36 96.60 farm 16 10.3 81.4 5.8 1.2 11.6 1.98 139.25 61.54 169.23 farm 14 16.3 88.2 3.7 0.7 7.4 1.42 99.49 43.48 128.70 farm 3 12,4 93.7 4.8 1.5 0.77 55.58 24.66 61.22 farm 2 7.3 87.7 12.3 1.04 76.71 35.14 91.14 farm 4 10.3 94.2 5.8 0.76 54.67 24.22 72.44 farm 9 6.3 90.5 9.5 1.05 76.33 34.50 96.33 farm 6 11.0 94.5 5.5 0.91 65.12 28.76 84.30 farm 10 3.6 83.3 16.7 1.03 76.57 36.00 96.00 farms 4.6 87.0 13.0 1.02 75.11 34.67 96.89 farm 15 6.0 i 00.0 2.01 140.94 60.40 201.34 farm 1 3.0 90.0 10.0 0.40 29.20 13.20 34.67 farm 5 6.3 90.5 9.5 0.75 54.20 24.50 68.40 farm 11 8.6 93.0 7.0 1.23 88.29 39.43 119.43 farm 12 11.0 94.5 5.5 1.10 78.80 34.80 102.00 AVERAGE* 8.8 90.4 8.0 0.9 9.6 1.01 72 J3 32.16 91.63 ' average for all 16 farms Tab. 2.20: Land use and yields on farms in the karst region, Slovenia, 1994. ■s s n o t>. M Is 1 i •n © o o «n II 1 »» o qoqooooooopcsoqoo 2 i ä 5 a cn S 1 « 'S u 1 »ft r- O «SP S ž B S CO »o f«S K CO cn S ^ lo s>| s z r; i ae S o s tj «! 5i S m 2 1 It 2 « cÄrsiqoq-^r-vcots^oqcor^-^, >oq 1 in 1 CMCOO^^^CO^OOOvMt-fO^C^O s 1 1 i |1 1 ^ i 9\ 1 s ä S t» 1 120 100 • . 1 t« •C 80 - i S 60. ^ a. o: m average (42 kg N/ha) — z lU § o: 1- 20 ^■nniiiii z 0 ■ ■niiiiiiiil -20 ■ ■ FARMS Fig. 2.32: Gross nitrogen balance, farm level, Trnovsko-Banjška Planota. a 80 in 3 (0 Z III i» t average ( 34 kg N / ha) iiiiiii ill FARMS Fig. 2.33: Net nitrogen balance, farm level, Trnovsko-Banjška Planota. Tab. 2.21: Nitrogen balance, farm level, Trnovsko Banjška planota. INPUT OUTPUT BALANCES 1 2,1 1 2,2 1 2,3 3 4,1 1 1 .4,2 Nitrogen Nitrogen from agric. production Nitrogen Nitrogen balances from the Mineral Liquid Total uptake Gross Net atmosphere fertilizer manure N supplay balance balance Region kg/ha kg/ha kg/ha kg/ha kg/ha kg/ha kgyha SLOVENIA 1991 15.5 47.2 «9.8 137.0 70.8 66.3 56.3 SLOVENIA 1992 15.5 43.5 «1.1 124.6 53.3 71,3 62.5 SLOVENIA 1993 15.5 57.3 «1.9 139.2 52.1 87.1 78.1 SLOVENIA 1994 15.5 60.7 77.5 138.3 91.0 47.2 39.5 farm 7 15.5 0.0 66.2 66.2 37.5 28.6 24.3 farm 13 15.5 18.4 74.9 93.3 38.2 55,1 48.1 farm 16 15.5 15.4 139.3 154.6 41.1 113.5 87.2 farm 14 15.5 53.0 99.5 152.5 59.0 93.6 79.2 farm 3 15.5 . 13.1 55.6 68.7 69.0 -0.3 -1.4 larml 15.5 0.0 ■76.7 76.-} 82.5 -5.8 -13.3 farm 4 15.5 1.1 54.7 55.8 42.2 13.6 12.7 farm 9 15.5 7.5 76.3 83.8 42.5 41.3 33.9 farm 6 15.5 3.7 65.1 68.8 40.6 28.2 24.2 farm 10 15.5 4.3 76.6 80.9 39.4 41.5 34.0 farms 15.5 0.0 75.1 75.1 40.8 34.3 27.3 farm 15 15.5 0.0 140.9 140.9 37.9 103.0 76.3 farm 1 15.5 0.0 29.2 29.2 37.7 -8.5 -1.8 farm 5 15.5 10.2 54.2 64.4 37.6 26.8 26.0 farm 11 15.5 0.0 »8.3 88.3 41.8 46.5 35.5 farm 12 15.5 16.0 78.8 94.8 41.3 53.5 45.4 AVERAGE* 15.5 10.5 72.3 82.9 47.0 35.9 29.7 * average for alii 6 ferms column 2.3-2.1+2.2 col- 4.1-21 + 2.2-3 col 4.2-1+21+2.2«0.7-3 au 70 j i ■■ 50 CO ^ S 40 a < VI average (28 kg P / ha) £ 1 20 iinlll 10 - —111111111 -.11II1 LLLL farms Fig. 2.34: Phosphate balance, farm level. Trnovsko-Banj ska Planota. Tab. 2.22: Phosphate and potash balance, farm level, Trnovsko Banj ska planota. PHOSPHATE POTASH 1,1 u 2 3 1>1 M 2 3 Mineral Liquid Uptake Balance Mineral Liquid (Tptake Balance fertilizer manure fertilizer manure Region kg/lia kg/ha kg/ha kg/ha kg/ha kg/ha kgflia kg/ha SLOVENIA 1991 35.5 89.8 29.8 95.5 55.8 89.8 74.0 71,7 SLOVENIA 1992 36.4 81.1 22.5 95.0 56.6 81.1 54.8 83,0 SLOVENIA 1993 48.7 81.9 22.4 108.1 75.6 81.9 52.8 104,8 SLOVENIA 1994 42.0 77.5 37.7 81.8 66,8 77.5 97.8 46,5 farm 7 6.2 29.0 12.5 22.6 0.0 82.9 45.1 37,8 farm 13 18.4 33.4 12.9 38.9 18,4 96.6 46.8 68,2 farm 16 15.4 61.5 13.9 63.1 50.0 169.2 50,5 16S;7 farm 14 53.0 43.5 21.8 74.7 60,0 128.7 72.3 116,4 farm 3 13.1 24.7 26.6 11.2 24.4 61.2 82.4 3,2 farm 2 0.0 35.1 32.6 2.6 0.0 91.1 101.1 -10.0 farm 4 1.1 24.2 14.1 11.2 1.1 72.4 51.0 22.5 farm 9 7.5 . 34.5 14.8 27.3 7.5 96.3 55.5 48.3 farm 6 3.7 28.8 13.6 18.9 3.7 84.3 48.9 39.1 farm 10 4.3 36.0 13.2 27.1 4.3 96.0 48.0 52.3 farms 0.0 34.7 13.7 21.0 0.0 96.9 49.5 47.4 farm 15 0.0 60.4 12.7 47.7 0.0 201.3 46.2 155.1 farm 1 0.0 13.2 12.6 0.6 0.0 34.7 45.6 -10.9 farms 10.2 24.5 12.6 22.1 3.6 68.4 45.3 26.7 farm 11 0.0 39.4 14.8 24.6 0.0 119.4 52.7 66.8 farm 12 16.0 34.8 13.9 36.9 52.0 102.0 51.0 103.0 AVERAGE* 11.1 32.2 16.6 26.6 15.9 91.6 57,2 50.3 ' average for all 16 farms column 3 = 1.1 + 1.2-2 5l Of z> OT 1 avei^ge (58 kg K / ha) FARMS Fig. 2.35: Potash balance, farm level, Tmovsko-Banjska Planota. Taking into consideration all the evaluated average data it could be concluded that the region Trnovsko-Banjška Planota can not be identified as vulnerable for nitrogen leaching into the groundwater. But in these regions with limited growing conditions for agricultural crops (climate, soil depth) just small increase in livestock density can cause nitrogen surpluses over 100 kg N/ha. For this reason the restrictions regarding application of chemical fertihser and manure on hilly and karst regions have to be more rigorous than in plains. On the other hand it was found out that in many cases dung yards and cesspools on farms are not built and/or are poorly built. In this case hquid manure can cause serious problem as being point polluter of groundwater. 2.7.2.5. National nitrate policies There are several regulations in force in Slovenia that are supposed to control water and food quality in connection to nitrates. Slovenian legislation is quite strict as far as standards on drinking water, food quality or quality of agricultural products is concerned regarding nitrate (as well as other chemical elements or toxic substances). According to EU Nitrate Directive the maximum standard for nitrate in drinking water (according to adopted value by WHO) is 50 mg NO3/I of water. (SOREN & BOIE 1994). Slovenian legislation on the other hand has set up standard of maximum nitrate content in drinking water being 44 mg NO,/l of water. Bottled water is not supposed to contain any NO^, while regular water is allowed to contain up to 0,005 mg/1 of NO^" N under regular conditions and not more than 0,05 mg/1 of NO^ N in irregular conditions. And if our Slovenian legislation, which almost entirely corresponds to Nitrate Directive and Code of Good Agricultural Practice, is followed and obeyed, there should be no fear in future to expect the agriculture to be polluter of ground water and surface waters. The most important regulation regarding expected processes of change in agriculture is supposed to be The Regulation on animal excrement's management. This regulation gives different norms. The most important are the following: a) The highest quantity of manure allowed to be used on agricultural land as well as limitations for the use of the manure in specific soil conditions: - The maximal allowed intensity of raising animals is 3 LU/ha for cattle or 2 LU/h for pigs and poultry. - Application of organic manure is not allowed during winter time on frozen soil. - Application of organic fertiliser is not allowed on soil saturated with water. - Application of organic fertiliser is not allowed in temporarily flooded areas. - Application of organic fertiliser is not allowed near water streams (10 m away from the stream) and in the depressions where there is no run-off of water. - It is not allowed to apply liquid manure on bare soil in the period from Nov. .15 till Feb. 15. - Application of organic fertilisers on water aquifer protected areas has to be done in agreement with the local regulations valid for those areas. - In the vicinity of spring water and in underground water pumping areas waste water can not be drained to spring water or underground water in any case. b) The highest quantity of N, P^O,, and K^O allowed to be used per hectare is 210 kg N, 120 kg Pp. and 300 kg Kp. c) Animal wastes should be stored in a suitable arranged dung yards and cesspools. Dung yards and cesspools are supposed to be arranged in the way that there is no danger of leaking through and pouring over the underground water. d) It is set up 5 years grace period needed for the adjustment of farms to these regulations as follows; - the adjustment of the number of animals (LU) according to the area of land available on the farm, - possible rent of additional land according to the contract, the construction of necessary dung yards and cesspools for hard and liquid manure according to the restrictions. The extension service is obliged to take care of the transfer of necessary knowledge to the farmers. The control over implementation of mentioned regulations is supposed to be done by agricultural inspection, belonging to Ministry of agriculture. 2.7.2.6. Conclusions Nitrate leaching into ground water and surface waters influenced by agricultural production is supposed to be a problem in the karstic region of eastern Slovenia - Trnovsko-Banjška Planota under certain conditions; point source pollution due to the lack of dung yards and/or cesspools or higher concentration of animals per ha can cause the problem with nitrate pollution in the groundwater. Therefore a nitrate policy is being in the phase of preparation in order to reduce mineral surpluses in agriculture and to meet the standards of nitrate in drinking water. Mineral balances at national, regional and farm level were calculated based on the 'corrected normative approach'. In Ajdovščina community and Trnovsko-Banjška Planota region the nitrogen net-balance surplus is less than 36 kg N/ ha while average net-balance surplus for Slovenia is about 56 kg N/ha. In Trnovsko-Banjška Planota the average yields and uptake by crops are low and therefore non-point source pollution caused by mineral fertilisation in this region is not considered a serious problem. The high nitrogen surpluses can be caused by high animal density per ha. The stocking rate over 2,1 LU/ha can cause net-balance surplus over 100 kg N/ha; in this case organic fertilisation can be considered a serious pollution source The average net nitrogen surplus in private farms in other parts of Slovenia is 46 kg/ha. It is a little bit higher than Slovenian average in 1994 (40 kg/ha). While in state farms is nearly three times higher than Slovenian average - 117 kg/ha. In the Karst region of Trnovsko-Banjška Planota with limited growing conditions for crops (climate, soil depth, shallow soil) just small increase of livestock density can cause considerable nitrogen surplus. For that reason the restrictions for the application of chemical fertiliser and manure on hilly karstic regions had to be more rigorous than in plains. Slovenian legislation intends to level this situation with quite strict regulations which are in agreement with EC Nitrate Directive and Code of Good Agricultural Practice. 2.8. FAUNA IN SELECTED KARST SPRINGS FROM THE TRNOVSKO-BANJŠKA PLANOTA (A BRANCELJ) 2.8.1. Introduction Copepoda is one of the most diverse and widespread group of so called "lower crabs - Entomostraca". Their body size usually ranges between 0.5 and 3 mm (HUYS & BOXSHALL 1991; EINSLE 1993). In inland waters they occupy very diverse of habitats, particularly taxa from groups Cyclopoida and Harpacticoida. They inhabit all types of permanent waters as well as some perennial ones (as for example puddles). They are very common members of subterranean communitus in sinking rivers, springs and percolating water. In sinking river abundance and number of epigeic species decline along the river, but number of subterranean taxa increase (BRANCELJ 1986). In percolating waters prevail stygobitic taxa, also in rare occasions some epigeic taxa are found there. This happens when thickness of ceiling is small and epigeic water bodies are in a vicinity. There is a lot of endemits among subterranean taxa, especially in that inhabiting percolating waters (SKET & BRANCEU 1992). In some springs beside specimens of Copepoda, Ostracoda, Amphipoda, Ephemeroptera, Plecoptera and Coleoptera are present, too. In the area of the "Karsthydrogeological Investigations in SW-Slovenia" within the framework of the ATH-project we made in 1993 a preliminary analysis of copepod fauna in four springs. No similar work has been carried out in those springs before. The aim of analysis was to locate the sites with hypogeic taxa, i.e. cave-dwelling species, especially that of Copepoda. Selected sampling localities were: the spring of the Vipava river, the caption in town Vipava, spring Kajža and spring Ajba. Sampling took place on March 23 1993. Material was collected by hand net with mesh size of 60 /u,m. Samples were stored in 4 % formaldehyde solution and transferred to a laboratory, where we use stereo microscope to pick out specimens of Copepoda, Amphipo-da, Plecoptera and Ephemeroptera. Only specimens of Copepoda were determined to the species level, using determination keys of DUSSART (1967, 1969) and PETKOVSKI (1983). 2.8.2. Results Nine species of Copepoda were determined; eight of them belong to group Cyclopoida and one to Harpacticoida. Undetermined specimens of Ostracoda, Amphipoda and Plecoptera were present in spring Kajža, too (Tab. 2.23). Specimens of Amphipoda are probably Niphargus cf. stygius, known from some localities nearby. Five copepod species from Table 2.23, out of nine, are known as stygobitic, i.e. they live exclusively in subterranean habitats. Two of them, Diacyclops slovmicus and Elaphoidella cvetkae,_ are known from relatively small area. Tab. 2.23: Faunistic list and localities; stygobitic taxa are indicated with asterisk. spring of Vipava caption in Vipava Kajža Ajba CYCLOPOIDA ♦Diacylops clandestinusKiefer, 1932 XXX *Diacyclops languidoides (Lilljeborg 1901) XXX Diacyclops languidus (Sars, 1863) XXX •Diacyclops slovenicus Petkovski, 1957 XXX *Diacyclops zschokkei Kiefer, 1931 XXX Eucyclops serrulatus (Fischer, 1851) XXX Megacyclops viridis (Jurine, 1820) XXX XXX Paracyclops fimbriatus (Fischer, 1853) XXX HARPACTICOIDA ♦Elaphoidella cvetkae Petkovski, 1983 XXX OSTRACODA XXX »AMPHIPODA XXX XXX PLECOPTERA XXX XXX Ostracodans are represented by shells only and detail determination was impossible. Shells were of different shapes and they probably belong to at least two species, one of them with restricted distribution. Amphipodas are represented by few young specimens of genus Niphargus. Representatives of this genus are common in different types of underground waters. Plecoptera is one group of insects. In two locations Plecoptera were represented by larvae. Whilst adults fly around, mate and lay eggs in water, larvae develop in water. They are very sensitive to organic or inorganic water pollution and are indicators of ohgosaprobic water status. Adult females in some species prefer to put their eggs into springs, usually quite far from the entrance. 2.8.3. Discussion One location, caption in town Vipava, has no animals at all, due to the fact that the water flow was too fast and therefore no animals can persist. In spring of the Vipava we sampled just at the mouth of the spring. Fauna there was poor. We got only three taxa of Copepoda, beside some specimens of Mollusca {Bythinia sp.). All three taxa of Copepoda are known from epigeic habitats, including surrounding of springs. They are among the most common, and tolerant, species of Copepoda. According to previous experiences, they out competed (or preyed) subterranean species in springs. The most interesting fauna we found in spring Kajža, actually in small puddle, c. 10 m from the entrance. Beside larvae of Plecoptera, which originated from outside, we found three interesting taxa of Copepoda: Diacy-clops languidoides, D. slovenicus and Elaphoidella cvetkae. Whilst Diacyclops languidoides is common also in subterranean waters, are D. slovenicus and Elaphoidella cvetkae exclusively inhabitants of subterranean waters. We found them in SW part of Slovenia and in vicinity of Triest (Italy). Finding of both taxa indicate that water coming to the spring has no direct connection with epigeic water bodies. Origin of water in spring is solely percolating water. Similar situation we found in spring Ajba. Specimens ofD. zschokkei andD. clandestinus, beside Niphargus sp., indicate that water in the spring has no direct connection with epigeic water bodies. Few specimens of Megacyclops viridis found together with previous mentioned taxa shed slightly different light on the problem. M. viridis is a very common species in many oligotrophic and slow-running epigeic water bodies. At the same time it is common in sinking rivers quite far from the sink hole. Presence of specimens of M. viridis in spring Ajba is probably a result of human transport with water from somewhere else and not via water channel through the massif. Springs Kajža and Ajba can be considered, according to fauna composition. as springs with juvenile water, i.e. water filtered through soil and bed-rocks. Fauna doesn't confirm any direct connections between constant epigeic water bodies and mentioned springs. At the same time it doesn't exclude any connections through dry channels, or temporary overflowed channels, in the recharge area. Presence of relatively rich subterranean fauna, with relatively small number of specimens indicate that concentration of organic material, like communal sewage or water from waste dumps, is low. 2.9. VEGETATION CHARACTERISTICS OF THE TRNOVSKI GOZD (T PIPAN) Trnovski Gozd can be placed in the Dinaric phytogeographic region but forms its extreme north-western part. There is represented, therefore, a kind of transitional zone between the Dinaric and Alpine phytogeographic regions. This is most clearly reflected in the smaller number of Dinaric (Ilyric) samples of flora and the larger number of Alpine species. The southern margin of the Trnovski Gozd towards Vipava valley forms the direct border with the Submed-iterranean phytogeographic region. Because of the configuration of the terrain, the border is very sharp in places, the zone of transitional vegetation being mostly narrow. Due to its characteristic geographical position. Trnovski Gozd is a kind of cross-roads of different species of flora in miniature. At the margin towards Vipava valley and on up the Čepovan valley, there are examples of quite a number of Submediterranean species. On the plateau, however, the Dinaric-Ilyrian meets with the Alpine. The most well known tract with all three types of flora mixed is Čaven where an extraordinary variety of flora flourishes. The Paleoendemit parsnips discovered by HIadnik, Hladnika pastinacifolia also thrive in the Trnovski Gozd, growing only on the Čaven and Poldanovec. The reason for the mixture of species, is not known; studies show that neither darkness nor temperature are causes. The entire plateau of the Trnovski Gozd, except frost place tracts, is covered with the Dinaric plant association of beech and fir {Omphalodo -Fagetum s. lat.). A height zone at between 900 to 1,000 meters and 1,300 to 1,400 meters is formed in the Dinaric phytogeographic region. The combined beech and fir forest grows on other tracts of our mountainous karst (Snežnik, Javorniki, Hrušica and Kočevski Rog) besides in the Trnovski Gozd. It is distinguishable from the similar plant association of our Alpine tracts by the presence of Dinaric-Ilyrian species in the undergrowth and by the presence of a number of Central European species. However, the number of Dinaric-Ilyrian species are considerably less when compared to other tracts of the mountain karst as the Trnovski Gozd represents a kind of transitional zone between the Dinaric and Alpine regions. Another type of vegetation in the Trnovski Gozd, is spruce. Spruce in the Dinaric region does not form a particular high zone alone but only when combined with beech. Real forest communities are only formed on the level plates with ground from chert (Mala Lazna and Velika Lazna) and in the sinkholes of Smrekova Draga. The reason for this, is the real characteristic of a frost place for these tracts. The Phytosociological forms two associations. The first is the Dinaric Subalpine spruce forest (Lonicero caeruleae - Piceetum), the second, spruce (Stellario montani - Piceetum) which is spread over Mala Lazna and Vehka Lazna. In the Dinaric phytogeographic region, the last forest zone of beech grows, that is that belonging to the association, Subalpine beech, Polysticho lonchistir - Fagetum s. lat. Beech in this association is no longer a tree but rather more a bush which, towards the border of the forest, grows as low as two to three meters. On the margins of the Trnovski Gozd, towards the Vipava valley, beech belonging to the Submediterranean association, Seslerio -Ostryetum grows. In the narrow or wide zones which are still influenced by Submediterranean flora, grows a special association, Seslerio - Fagetum which represents the encroachment of the beech forest into the mountain forest of the karst (ZUPANČIČ et al. 1987). Frost places Frost places are extreme types of biotops. In the orographic, ecological and botanical respect, they are sharply distinguishable from their surroundings. Due to different causes, their temperature regime is considerably sharper than in their surroundings, determining the thriving of plant life. The majority of frost places are on the mountain karst but they also exist in the Alps and even in the Submediterranean tracts (MARTINČIČ 1977). Mala Lazna Mala Lazna is a frost place formed on acid chert. During the day, there is no difference between the limestone parts and the chert but at night there is great radiation of heat and on the chert, the ground cools to below 0° C. The frost place is consequently formed due to nightly temperature inversion. The thickness of inverse layers of air is two to four meters. A specific temperature regime is formed, the result of the chemical reaction of the ground. Here thrives fir which likes the cold more than beech. Most probably, the beech has disappeared due to thinning out and this has caused a biological imbalance. Trees in the association have normal growth. The sporadic examples of changed appearance (e.g. more than one top) is due to temperature inversion. The spruce in the association have considerably smaller top growths; there is no difference in thickness, which is not unusual, because of different placing of photosynthates which does not limit this direction of growth (FILIPIČ 1959). Velika Ledena Jama V Paradani A funnel shaped sink hole, more than 50 meters deep, can be found on the plateau of Trnovski Gozd under Golaki. The bottom opens out as a pocket into a cave where there is ice and snow all year round. The lower part of the slopes are very gravely. There is an entrance to the ice cave on the shady side 1,090 meters above sea level where there is an opening in the mighty overhanging wall. Ground temperatures from the edge of the sinkhole downwards fall rather evenly. The lowest are close to the snow and ice where they come to 1 to 2° C all year. Because this part is always in the shade, the nightly oscillation is only some tenths of a degree. The difference between the surface and lower layers of ground is equally as great. The air temperature regime is inverted in sunny weather only at a height of 0,5 meters above the ground as the ground layer of air may heat up to 30° C on the foundation of the ground. Only in cloudy weather, this effect doesn't exist so the inversion is expressed over the whole ground profile of air. The temperature inversion which causes vegetation inversion means the air temperature from the edge of the sinkhole downwards falls and, in parallel, the temperature of the ground also falls. Temperature inversion is best seen if the temperature is measured on the vertical profile. Usually a real temperature inversion develops only on the parts which are always in the shade. On the slopes, which are exposed throughout the day to sun insulation, the surface can be strongly warmed along with the air at ground level. At this time, temperature inversion is formed only at the height of one meter where the air is not warmed by the ground. BECK (1906) is verified by the ice cave in Paradana where there is a classic example of vegetation inversion as zones of vegetation are the other way around than in the Alps. The inversion is almost perfect, there being missing only the zone of dwarf mountain pine. Analysis of the flora demonstrates that the zone is developed and we call it zone of Subalpine bushes only that its structure is fragmented and dwarf mountain pine {Pinus mugo) is missing. As this species is quite common in the Trnovski Gozd, it is questionable whether its presence is primary or secondary (MARTINČIČ 1989). From a floral-vegetation and ecological view point, we distinguish between the following zones in the Paradana: the zone of Dinaric beech-fir forest, the spruce zone, the zone of willow, the zone of Subalpine bushes, the zone of alpine herbs and the zone of mosses. Total inversion is exclusively present only on the exposed slopes, the east and west inclines chiefly offer a different picture (ZUPANČIČ 1980). The zone of beech and fir forest (Omphalodo - Fagetum s. lat.) starts approximately 30 meters above the cave entrance and grows all around the area. The spruce (Lonicero caemleae - Piceetum) zone covers only a small area. There are present progressively worsening conditions for growth in the down- ward direction and this is reflected in the size of the spruce. On the zone's lower edge, spruce thrives only in the form of bushes less than two meters high. The zone of willows (Salicetum appendiculate) represents conditions as they are at the height of the forest border as they are very common there. This is also confirmed by other species thriving in this zone. The height of the willow is dependent on temperatures which change quickly on the downward slopes. On the upper border they reach some 3,5 meters high, on the lower only 25 centimetres. The zone of Subalpine bushes (as a fragment of the association Pinetum mugi), in the phytocenological and ecological sense, is a zone of dwarf mountain pine. However, for unknown reasons, the most important species is missing. The floral inventory of the zone is very rich. Among the species preserved by the ice case are also glacial relics such as the remains of ice age flora which at this time was common in the Trnovski Gozd. The most important species are: Rhododendron hirsutum, Rhodothamnus chamaecistus, Salix retusa (willow), Carex feruginea (sedge) and Valeriana saxatilis (valerian). In the zone of Alpine herbs there is a distinct mountain micro-climate. Lower temperatures, and with this worsening living conditions on the downward slope, prevents the thriving of the more demanding lignificated plants. Floral inventory is very poor. Here there thrives exclusively, cold loving species. The willow, Salix retusa is the only tree but Alpine meadow grass (Poa alpina), the two petal violet {Viola biflora) and the speedwell {Veronica lutea) can also be found. Around the cave entrance, in the vicinity of snow and ice, is a zone of mosses. The whole area is always in the shade; temperatures are always between 1 and 3° C. Extreme micro-chmatic conditions prevent the thriving of flowers. The only exception to this is the species alternate-leafed golden-saxifrages {Chrysosplenium alternifolium) which is, however, often sterile or even stunted. Low temperature is not the only cause of the absence of flowers, too little hght also plays a part; it is insufficient for netophotosynthesis. Frost places on conglomerated ground Cold loving vegetation in the sink holes grows especially on part of the slope, less or not at all on the bottom. In any case the ground is skeletal, gravely or conglomerate. It is composed of relatively rough material with air spaces in between which are interconnected in an uninterrupted system. The skeletal ground is mostly due to crumbhng of rock walls so frost places of this type are mainly in collapse dolines; they can also be found on open slopes. The ground at the lower part of the conglomerated slopes is the coldest. Between the skeletal material, can be found greater or smaller holes and fissures from which blows very cold air. The strongly cooling air circulating in the ground is the most important factor for its coldness. Sometimes its effect is so great that the whole surface layer of the ground, in spite of intensive insulation, can not warm up. Air enters the upper part of the slope in a system of fissures and spaces where cooling is witnessed. Because it is heavier, it slides into the internal downwards with additional cooling; in the lower part of the slope, it comes from the fissures. However, this method of cooling only, is not sufficient. Ice is sure to form at unknown depths which has a stronger cooling effect. In the sinkholes, the ground temperature is lower in the downward direction and, as a rule, is lowest just before the bottom. The temperature can be more or less equal on the whole profile of the sinkhole. Only in the depths of the sinkhole, with steep inclines, temperature inversion in the air layer can be found at the same time which can be some metres wide. Always the night temperature is inverted (MARTINČIČ 1989). Smrefcova Draga (Photo 13) The Smrekova Draga frost place is an extensive karst hollow on the northern side of Mali Golak. It is approximately 140 meters deep; its bottom is 1,100 meters above sea level. The sink hole lies in the climatic zone of the fir association, Omphalodo - Fagetum s. lat. which covers the higher parts of Photo 13: Smrekova Draga karst depression with vegetation inversion (Photo by P Habič). the slopes and the whole surroundings. The foot and lower part of the inclines are covered with spruce and dwarf mountain pine. The only reason for the changing vegetation conditions is the very cold ground and not temperature inversion. In the dwarf mountain pine zone, the temperature does not exceed 5° C all year. In the spruce zone it is 5 to 10° C and in the beech-fir zone the temperature is at least 10° C. In sunny weather, the ground's surface is heated strongly so there is a difference between deep and surface layers of 20° C and more. The air temperature does not show any inversion except at night. Often the highest air temperature is at the base in the zone of dwarf mountain pine. The temperature oscillates during the day and night, increasing towards the base as the nightly air temperature falls below 0° C even in summer. Extreme micro-climatic conditions affect the thriving of two cold loving communities. Lonicero caeruleae - Piceetum grows over most of the sinkhole and in the western part, Pinetum mugi. The border between spruce and dwarf pine is very sharp. The transitional zone of low spruce doesn't exist as the height of spruce at the edge is almost the same as in the association. The zone of dwarf mountain pine is limited to the coldest ground. It flourishes all over where the ground temperature at 20 to 30 cm deep does not exceed 1 to 6° C in the summer. In many places the ground temperature is only 1 to 2° C. It is not surprising that, on such ground, dwarf mountain pine grows to barely 0,5 meters although at the edge it is 3,5 meters high. From a vegetation point of view, the dwarf mountain pine is a fragment of the alpine association Pinetum mugi. Vegetation is sparse with most Alpine species. Sphagnum nemoreum, Vaccinium uliginosum and Oxycoccus palustris represent specialities forming on smaller surface areas of the high marshland. * New names of associations: MARINČEK, L., MUCINA, L., ZUPANČIČ, M., POLDINI, L., DAKSKOBLER, I., ACCETO, M., 1992: Nomenklatorische Revision der illyrischen Buchenwälder (Verband Anemonio - Fagion).- Studia Geobotanica, 12, 121 - 135, Trieste. ZUPANČIČ, M., 1994: Popravki imen nekaterih rastlinskih združb v luči novega kodeksa. Hladnikia, 2, 33 - 40, Ljubljana. 3. INVESTIGATIONS OF THE WATER BALANCE (1993-1995) 3.1. HYDROLOGICAL INVESTIGATIONS IN THE AREA OF THE TRNOVSKO-BANJŠKA PLANOTA PLATEAU BETWEEN 1993 AND 1995 (N TRIŠIČ) The equipment at the gauging profiles that existed before 1993 in the area under investigation was not satisfactory for the forthcoming investigations. The gauging profiles were only equipped, except for the profiles on the Lijak and the Idrijca, with gauging staffs where water levels were usually read only once a day. For a more detailed registration of water waves and the establishing of water regime, we installed in summer 1993, even before the first tracing experiments were performed, water level recorders (LP) at the most important gauging profiles (Tab. 3.1). The positions of individual hydrological stations are presented in chapter 2.2, Figure 2.9. Tab. 3.1: Gauging profiles, installed in the framework of the ATH investigations. Gauging profile water level recorder operating since 8630 The Hubelj-Ajdovščina April 01, 1993 8560 The Vipava-Vipava June 17, 1993 8350 The Idrijca-Podroteja June 24, 1992 8345 The Idrijca-Fežnar May 4, 1994 Since a part of investigations was focused on the catchment area of the Vipava springs, an additional observation and gauging network was established in this area, which operated from July 1993 until the end of 1995; only the operation at the Bela-Sanabor profile began later due to the troubled water level recorder (Tab. 3.2). Tab. 3.2: Additional gauging profile with LP - water level recorder; VP - staff gauge. Gauging profile Station operating since 8546 The Belščica-LP Bukovje July 27, 1993 8547 The Lokva-VP Predjama August 25, 1993 8549 The Vipava-VP Pod Farovžem September 14, 1993 8602 The Bela-LP Sanabor January 1, 1994 8603 The Bela-VP Vipava July 27, 1993 With the existing network of hydrological stations it was not possible to register discharges of the Divje Jezero and the Podroteja springs, which both join the Idrijca above the Idrijca-LP Podroteja gauging profile. Therefore, we also installed an additional station with water level recorder in 1994, on the profile 8345 the Idrijca-Fežnar. Since the distance between the profiles the Idrijca-Podroteja and the Idrijca-Fežnar is rather short (4.3 km), the difference in discharges between the both profiles can be taken as the discharge quantity from the both karstic springs. Yet, due to the torrential hydrological regime of the upper Idrijca and the Bela, and the short string of observations, we did not succeed to register so high discharges to be high enough to establish the upper part of discharge curve. For the four representative hydrological stations (Compare Chapter 2.2.) which register the most important outflows from the karstic massif, the data were processed for the investigation period from August 1, 1993 to December 31, 1995, and comparatively, also for the period of two hydrological years, from November 1, 1993 to October 31, 1995. The Hubelj - LP Ajdovščina Presented are the data on daily heights of precipitation at the precipitation station Otlica (835 m above sea level), and the mean hourly discharges of the Hubelj at the gauging profile (Fig. 3.1). The maximum daily precipitation (143 mm) fell on December 27, 1995, and the second maximum of daily precipitation (134 mm) occurred on November 17, 1995. The majority of precipitation at the station Otlica fall, on the average, as to the 1961-90 period, in the autumn months (704 mm), while the shares of precipitation in the other seasons of a year are practically equal (562 mm; 587 mm; 559 mm). The discharges of the Hubelj in both the discussed periods do not stand out from the frame of statistical values for the 1961-90 period. Both value of the mean discharges is only by approx. 10 % above the mean discharge of the Precipitations: OtIIca JUUJ jJIIILL JL 10.00 0.00 - DisehaiBesMubdj 1.8.1993-31.121995 1.11.1993-31,10.1995 , 20999 Number of numeric cdls 17350 Number of numericpells Inlllina . 7004S.73Sum 52S31.51Sum lXApril94 3-33567 Average 3.033516 Average • Inj.üme I 4.«)2586 Standard Deviation 0.061 Minimum <0.741 Utoomum 3.826532 Standard DevlationI 1.Aug.95 0.061 Minimum ■ 34.59 Maximum ' VjJiJ i jL ^yi^ JLJ Fig. 3.1: Mean hourly discharges of the Hubelj spring at the gauging profile Hubelj-LP Ajdovščina and daily heights of the precipitations at the precipitation station Otlica. period. The maximum discharge in the shorter period of two hydrological years also coincides with the mean maximum discharge of the 1961-90 period (34.59 mVsec; 33.4 mVsec). When deahng with minimum discharges it should be emphasised that these data refer to discharges at the gauging station, and not to discharges at the Hubelj spring. There, a certain quantity of its water is tapped for the water supply of Ajdovščina and its surroundings, and also for the operation of the Hubelj hydropower plant. Evident in the hydrograph at lower discharges are the abnormal extremes in time distribution of discharges which are due to the hydropower plant operation. This influence on the discharges of the Hubelj had not been registered in the profile of the gauging station before the installation of a water level recorder. The lowest discharge of 0.061 mVsec was registered on August 5, 1994, when the regular maintenance works were performed on the sluice gate at the dam below the Hubelj spring. The exact data on the water quantity taken for water supply do not exist; but by approximate assessment, between 50 and 100 1/sec are taken on average, during the summer droughts, even up to 150 1/sec. 0.9 0.8 0.7 0.6 0.5 o 0.4-1 0.3 0.2 0.1 HUBELJ-LP AJ[X>VŠCINA:HOURS DISCHARGES 1993 0> O) 0> O) 0> 0> 0> 0> 0> 0> 0> 0> O) 0> O) o> o g> §> Ol g. g) g. ' S Fig. 3.2: Hydrograph of the Hubelj discharges during low water conditions in August 1993 exhibiting an explicit daily variation caused by water abstractions for both the hydropower plant and for water supply. On the hydrograph of the Hubelj discharges, an exphcit daily oscillation of discharges is evident at low water situation in August 1993, which is due to the tapping for water supply, while the oscillation on August 5 and 6 is due to the Hubelj hydropower plant operation (Fig. 3.2). Such oscillations are frequent because they occur at each disengagement or omission of turbine operation. On the basis of the registered minimum discharges and the known influences, the minimum discharge of the Hubelj spring can be assessed to amount to 0.250 mVsec. The Vipava - LP Vipava For the presentation of discharges at the Vipava springs and precipitation in the catchment area, the data were processed, from the station with a water level recorder at Vipava, and the precipitation station Nanos-Ravnik at the altitude of 915 m (Fig. 3.3). The height of precipitation here is lower (the average of 1834 mm) than at the station Otlica. The largest daily quantity of precipitation fell on October 29, 1994 (99.8 mm), and the second maximum of the discussed period occurred on August 29, 1995, with 91.6 mm of daily precipitation. In this area, too, the majority of precipitation fall in the autumn months, 524 mm on average, and in the remaining seasons, the heights are essentially lower (399 mm; 447 mm; 468 mm). Dischaws^V*»» ,,(^»„.1 16A|lril ItM I I 1.8.199:}^1.12.199S 21169 Numburofniimedccels 15954S.3Slll 7-M«r-«4 S £ o Dlacharg«: UJak lii|.tlme , 14.Oct.93' LIJAK 1.8.1993-31.12.1995 21169 Number of numeric celb I 23930 Sum lni.Bme , 1.125703 Average 1S.A|iril 94 ■ 2.874107 Standard Deuialion ) 0 Mnimum I 17.2M Maximum I 11.AP4S L|ak: 1.11.1993-31.10.1995 17520 Number of numeric c«la 13695.88 Sum 0.7817283 Average 2.238614 SUndard Devlatlcn 0 Mnimum 13.3S1 Muomum Ul N.tlme I.OctSS Fig. 3.4: Discharges of the periodical Lijak spring at the gauging profile Lijak-LP Smihel and daily heights of the precipitations at the precipitation station Lokve. discharge of 0.6 mVsec is lower than the mean discharge in the time of investigations, 1993-95 (1.12 mVsec and 1.00 mVsec). The Idrijca - LP Podroteja Due to the longer interruption of observations at the precipitation station Črni Vrh Nad Idrijo (683 m above sea level), the data on precipitation at the precipitation station Vojsko (1070 m above sea level) are comparatively presented for the station with a water level recorder the Idrijca-LP Podroteja (Fig. 3.5). On the average, the precipitation in the 1961-90 period were slightly higher at the station Črni Vrh (Črni Vrh - 2589 mm; Vojsko - 2450 mm), while in the individual precipitation situations, great differences can occur in the daily heights of precipitation. The maximum daily height of precipitation in the 1993-95 period amounted to 223 mm at the station Črni Vrh (on November 17, 1995), but only 102 mm at Vojsko. After the most abundant precipitation on November 17, 1995, only the height of 70 mm was registered Precipitations: Vojsko kl Ii Ii Discharges: Idrica - Podroteja 1.8.1993-3M2.I995 21169 Number of numeric cells 203436.7 Sum 9.610122 Average 17.35436 Stondcffd Devioti \.46l A/linimum 252.156 Maximum Mi tijection time: Apr. 16.1994 17520 NÜM&^ßraMdritfS&ils 151619.3 Sum 8.654068 Average >!>, (lilt. ■ lij, 14.S«33Ö 1.5« 227.05 Standard Deviation Minimum Maximum I I Irqection time: I Aug.1.1995 I I Fig. 3.5: Mean hourly discharges at the gauging profile Idrijca-LP Podroteja, which comprises the surface waters of the Belca and Idrijca as well as the discharges of the karst springs Podroteja and Divje Jezero and the daily heights of the precipitations at the precipitation station Vojsko. at the station Vojsko, and the next day, further 30 mm, which is less than a half of the daily precipitation at the stations Lokve and Črni Vrh. In the Idrijca-LP Podroteja gauging profile, the discharges are comprised, so from the surface part (the Belca, the Idrijca), as from the karstic part (the Divje Jezero-Jezernica, the Podroteja springs) of the catchment area. From the difference between the obtained discharges at the profiles the Idrijca-LP Fežnar and the Idrijca-LP Podroteja, the influx from the karstic part of the catchment area can be calculated; yet, these data are only representative of the situations when the gauging of discharges was performed (Tab. 3.6). Due to the time lag in reaction on precipitation of the karstic part of the catchment area, only the stable situations can be comparable, above all, at low water situations. Tab. 3.6: The gauged Podroteja (m^ I sec ). mately influx of the discharges at The difference karst springs the stations Idrijca-LP Fežnar and Idrijca-LP between both profiles represents the approxi- Date LP Fežnar LP Podroteja Difference Jun/07/94 1.250 4.762 3.512 Jul/26/94 0.357 1.870 1.513 Aug/30/94 0.991 5.658 4.667 Sep/27/94 2.802 4.679 1.877 Nov/23/94 0.814 2.635 1.821 Jan/31/95 1.82 11.12 9.3 Feb/23/95 2.22 11.41 9.19 Apr/26/95 2.60 6.96 4.36 Jun/14/95 2.51 11.78 9.27 Aug/17/95 0.51 1.991 1.481 Oct/05/95 0.806 3.327 2.521 Nov/23/95 1.583 6.13 4.547 Mar/19/96 1.225 5.289 4.064 May/09/96 6.315 15.235 8.99 Jul/03/96 8.373 63.183 54.81 The contribution of the surface part of the catchment area between the profiles Fežnar and Podroteja is negligible at low water situations (approx. 50 1/sec), but within the low mean discharges it already amounts to 0.3 - 0.5 mVsec. Nonparametric Spermann's correlation (Fig. 3.6) of the gauged discharges between both gauging profiles indicates the possibility of the occurrence of two populations and therefore, lower correlational dependence. The nonparametric Spermann's coefficient of correlation results in R = 0.83. From the presented data, it is not possible to determine the lowest discharge from the karstic catchment area. The lowest discharges in the 1993-95 period were still within the range of the characteristic mean low discharges (1.461 - 1.66 mVsec). Also the calculated lowest discharge from the karstic catchment area of 1.481 mVsec ranks, together with the discharge of 1.991 mV sec of the Idrijca on the LP Podroteja profile, into the range of mean low Fig. 3.6: Results of the nonparametric Spermann's correlation between the gauging profiles Idrijca-LP Fežnar and Idrijca-LP Podroteja showing the frequency distribution and the correlational dependence between both groups of data (N = 15). discharges of the period. However, it was not possible to determine the share of discharges from the karstic catchment area, neither at the lowest (0.840 mVsec) nor at the highest (306 mVsec) discharges of the Idrijca on the LP Podroteja profile, in so short a period of observations (from May 1994). For the assessment of contributing share of the remaining water springs in the investigated area, two series of gauging were completed, on the springs Hotešk, Avšček (below Bolterjev Zdenc) and Kajža, and on the ponor streams Slatna at Grgar and Čepovanski Potok (Tab. 3.7). Tab. 3.7: The gauged discharges of the karst springs Hotešk, Avšček and Kajža, of two ponor streams and of the Idrijca-LP Podroteja (m^/sec). Springs Apr/13/95 May/23/95 Hotešk 0.093 0.264 Avšček 0.018 0.043 Kajža 0.023 0.112 Altogether 0.134 0.419 Ponor Streams Apr/13/95 May/05/95 Slatna 0.013 0.048 Čepovanski Potok 0.012 0.020 Altogether 0.025 0.068 The Idrijca-LP Podroteja 2.91 5.01 It is assessed that the mean discharge of the gauged springs amounts to 0.8-1.0 mVsec. The most abundant is the Hotešk spring which is also the least investigated. Calculations Of The Quantities Of Recovered TYacers For the calculation of the quantities of recovered tracers the data were used, on the discharges at the hydrological gauging stations the Vipava-Pod Farovžem, the Hubelj-Ajdovščina, and the Lijak-Šmihel. The quantities of recovered tracers on the other springs of the Vipava, Pod Skalco and Pod Lipo, were calculated with the difference in discharges between the profiles the Vipava-LP Vipava and the Vipava-Pod Farovžem. In the analysis of tracers, the discharges at the sampling time were taken into account. The quantities were calculated by means of the following equations (1) and (2): xa,xQ (1) K,i - the quantity of tracer in the time between t|+l<^t.-l Q,; - the discharge in the time t. C,. - the concentration in the time t^ or: n I i=l tj+l + tj-l xQtiXQ (2) K - the total recovered quantity For the calculation of recovered tracers at the Mrzlek spring, the mean discharge was assessed on the basis of the mean ratio between the discharges at the profiles under observation (the Idrijca-Podroteja and the Hubelj-Ajdovščina) in the time of tracer occurrence in the Mrzlek, and the statistical value of discharge at both profiles in the 1961-90 period. With the obtained coefficient the datum was calculated, from the balance of the mean discharge of the Mrzlek in the period (10.12 mVsec), of the mean discharge of the Mrzlek in the time of an individual tracing experiment (Tab. 3.8). More details are given in Chapter 6. Tab. 3.8: The data base of the Mrzlek spring used for the estimation of the quantity of recovered tracer Due to technical reason only in 1995 sampling from both the Mrzlek-spring in the Soča (i) and from the pumping station (v) was possible. In 1993 and 1994 only samples from the pumping station are available. 1993 1994 1995 tracer presence: from - to 10/23 - 12/23 04/24 - 06/01 09/03 - 12/31 average concentration [mg/m^] 0.022 0.125 0.041(i) 0.038 (v) coefficients (k) used for the discharge estimation 1.7 0.9 1.2 average discharge Q = 10.12 • k 17.20 9.11 12.14 average discharge Q = 7.29 • k 12.39 6.56 8.75 3.2. THE WATER BALANCE OF THE TRNOVSKO-BANJŠKA PLANOTA (J. POLAJNAR, J. PRISTOV, M. BAT, M. KOLBEZEN) 3.2.1. Introduction By making water balance, the ratio was established between the average quantity of precipitation, evapotranspiration and water runoff into the border rivers in the area of the Trnovsko-Banjška Planota (TBP); the aim was to determine the shares of the underground drainage from the entire TBP, and of the still unknown drainage from the karstic massif into the area of the underwater spring Mrzlek. The water balance of the TBP plateau was determined for three periods. The thirty-year water balance (1961-1990) Following the WMO recommendations, the 30-year period, from 1961 to 1990, was to be taken into account for the study of hydrological and meteorological data over several years. The two-year water balance (1993 - 1995) For the period of two years the time when the tracing experiments were performed in the area of the TBP (Chapter 6) was used (November 1, 1993 to October 31, 1995). The five-year water balance (1991 - 1995) For the period of five years 1991 to 1995 was chosen as a comparison to the thirty-year and two-year hydrological balances. Two methods were applied for the calculation of water balance. With the first one, the runoff was determined, from the area of the TBP to the border rivers, the Idrijca, Soča and Vipava. No separation between the surface and the underground runoffs is included. With the second method, the runoff from the karstic area of the TBP was determined. For the discussed periods both the runoff conditions in the areas with the surface runoff, and the runoff conditions in the areas with underground runoff to the surface streams were separately calculated. 3.2.2. The method of establishing water balance for the area of the TBP without separation Following the described methods, the water balance was estabhshed for the 30-year period, from 1961 to 1990. The starting point for establishing the water balance was the calculation of the common, surface and underground runoffs from the area of the TBP, on the basis of the data on precipitation, evapotranspiration, and the data on discharges at the gauging stations on the border rivers and their tributaries. The catchment area which was taken into account, stretches over the entire upper Soča river basin, to the confluence with the Idrijca, the contributing basin of the Soča on its right bank between Most na Soči and Solkan, the Tolminka contributing basin, the contributing basin on the right bank of the Idrijca between Podroteja and the confluence with the Soča, the contributing basins of the Bača and the Cerknica, the contributing basins of the Vipava springs in the area of the Nanos, and the contributing basin on the left bank of the Vipava, between Vipava and Miren, and the contributing basins of the Močilnik and the Branica; the entire area measures 1337.5 sq km. The foregoing area was divided into 12 contributing sub-basins of which only the sub-basin no. 2 includes the contributing area of the TBP (Fig. 3.7). This is a part of the Soča contributing basin on the left bank, between Most na Soči and Solkan, the Idrijca contributing basin on the left bank, and the Vipava contributing basin on the right bank, between Ajdovščina and Voäomen» poiU}* Gauging atation Vodosljima cbmoeje TSP Conü-Ibutlng h^sin of TBP VodOBfeirna obmoöja. kl ne TSP \ CößtrlbuUag bÄBln« not drtlntej TBP \ Deteti odtolts Runoff porUoM 0 5 lOkm Fig. 3.7: Runoff from the TBP for the 30 years period (1961 to 1990) without distinguishing surface and underground discharge. Miren, with 832.8 km^. The remaining sub-basins with their contributing areas and rivers extend outside the area of the TBP; yet, their water quantities were taken into account in the establishing of water balance. For each sub-basin the database used consisted of the mean precipitation and evapotranspiration quantities in the period, as well as the discharges at the following gauging stations (VP) on the border rivers: Idrijca: VP Podroteja and VP Hotešk the Idrijca and the Soča confluence (calculated data) tributaries: the Cerknica-VP Cerkno the Bača-VP Baca Pri Modreju the Trebuša-VP Dolenja Trebuša Soča: VP Solkan VP Kobarid the Idrijca and the Soča confluence (calculated data) tributary: the Tolminka-VP Tolmin Vipava: VP Vipava VP Dolenje VP Dornberk VP Miren tributaries: the Močilnik-VP Podnanos the Branica-VP Branik the Hubelj-VP Ajdovščina the Lijak-VP Šmihel the Lijak-VP Volčja Draga the Vogršček-VP Bezovljak For the sub-basins without gauging stations, the mean discharges (sQs) of the period were calculated by discharge coefficients. With this method, the underground runoff is not separate from the surface runoff. Only the ratio was established between the precipitation and the run off water from the wider area of the TBP By eliminating the discharges from the contributing sub-basins outside the TBP, also the runoff from this plateau was determined. Following the foregoing method, the result was obtained for the wider area of the TBP; i.e., 34.92 m-^ of water was discharged per second, on average, from the wider area of the TBP during the period of thirty years: (TBI») (discharge to the Idrijca) ^^^ (discharge to the Soča) (discharge to the Vipava) sQs = 17.72 mVsec -f- 10.57 mVsec -f 6.63 mVsec (J BP) sQs = 34.92 mVsec The major share, i.e. 52.5 % into the Idrijca, 28.5 % into the Soča, and 19 % into the Vipava. The runoff coefficient for the hydrologically diverse area amounts to K = 0.57. The specific runoff of the thirty-year period amounts to 41.8 1/sec/km^. 3.2.3. The method of establishing water balance for the area of the TBP with the underground drainage The purpose of the second part of the water balance of the TBP was to obtain the underground runoff. By applying the method of gradual elimination of contributing sub-basins with the surface runoff, the runoff from the karstic contributing sub-basin, characterised by almost exclusively underground drainage, was calculated. Besides, the assessment was also made, of the discharge in the area of the underwater spring Mrzlek. This is the lowest lying karstic spring in the area of the springs at the western rims of the TBP where, hypothetically, the basic runoff from the karstic massif comes to the surface. The water balance and the assessment of discharge in the spring area of the Mrzlek were calculated by applying the described method, for the thirty-year, five-year and two-year periods. The area of the TBP was divided in detail to the sub-basins with the surface runoff and with the underground runoff. The karstic sub-basin with the underground runoff comprises the central part of the TBP with the major karstic springs: the Hubelj, Lijak, Mrzlek, the Podroteja karstic springs, and the Divje Jezero, and measures 348.5 km^ (sub-basin 108, Fig. 3.8). The mean discharge of the period from this sub-basin was calculated by applying the data on the mean precipitation quantities for the discussed periods (30 years, 5 years, 2 years) and the mean quantity of evapotranspira-tion for the thirty-year period. (Tab. 3.9). Tab. 3.9: The calculated mean discharges for the karstic area of the TBP plateau (Fig. 3.8: sub-basin 108) for the 30, the 5 and the 2 years periods. Sub-basin 108 30 5 2 with the prevailing years years years underground runoff Mean discharge of the period 20.02 19.43 18.32 (sQs in mVsec) Specific runoff (q in 1/sec/km^) 57.45 55.75 52.56 Runoff coefficient (k) 0.74 0.73 0.72 The water from the karstic massif comes to the surface in the karstic springs of which only the following were longer under the observations: the Hubelj, the Lijak, the Podroteja springs, and the Divje Jezero. For the calculation of discharges of the Podroteja springs and the Divje Jezero, the discharge of the Idrijca from the part of its contributing basin with the surface runoff above the gauging station and the karstic springs (sub-basin 41), was deduced from the discharge of the Idrijca at the gauging station Podroteja where the underground and surface runoff are joined (see also Chapter 3.1). From the assessment of discharges of the remaining karstic springs, the strongest of which is the underwater spring Mrzlek, the gauged mean discharges of the foregoing springs were deduced from the mean discharges from the karstic massif (sub-basin 108). 41 Vwaoracma ix»ta)ö Covigmg; station Vociozbimo območje s podzemmro odloiom .■1...J Contra bating area with subsurface jnjnoff Vodiosbinm obmoäja s pcvrdmsltim odtokom Contributing area wttb surface rvmo^Y C3aTne arnsri In 4ele£ odtoka Iz kreuBlcoiS«. masive rhe maiQ portions and dh^cticns of team karst massiff 0 JOkin _J Fig. 3.8: Runoff from the karst region of the TBP for the 30 years period (1961 to 1990). The difference is supposed to flow mainly into the Soča in the area of the underwater spring Mrzlek, and partly also with the other springs on the left bank of the Soča, between Most na Soči and Solkan: ^^^ Mrzlek SQS sub-basin 1Ü8 sQs Hubelj sQs Podroteja sQs Lijak The calculated discharges in the area of the Mrzlek spring are only an assessment of the actual discharges in the underwater spring (Tab. 3.10). Tab. 3.10: The calculated mean discharges for the catchment area of the Mrzlek spring for the 30, the 5 and the 2 years periods. 30 5 2 years years years Contributing sub-basin 108 with the prevailing underground runoff (sQs in mVsec) 20.02 19.43 18.32 Mrzlek spring area (sQs in mVsec) 10.12 9.80 7.29 In the 30-year and 5-year periods, the water from the karstic underground of the TBP was discharged as follows: a half of it to the Soča, one third to the Idrijca, and one fifth to the Vipava. While in the last two years, i.e. in the time of performing tracing experiments, 40 % was discharged to the Soča, 36 % to the Idrijca, and 24 % to the Vipava. The water balance for the 30-year period was established by applying both the described methods. Following the first one (without separation), the data on the gauged discharges were made use of for the contributing sub-basins with the gauging stations, and following the second method, the data were applied, on the discharges that had been calculated by making use of the precipitation and evapotranspiration data. Established was the average difference of 15 % between the gauged and calculated mean discharges of the period in individual contributing sub-basins. The theoretical discharge is by 15 % higher, on the average, than the gauged discharge. In case that the values of the calculated mean discharges of the period in the sub-basin with the underground runoff (sub-basin 108) are reduced by the foregoing 15 %, the mean discharges of the period in the Mrzlek spring area amount: 7.10 mVsec for the thirty-year period, 6.9 mVsec for the five-year period, and 4.54 mVsec for the two-year period. 3.2.4. Conclusions The results of water balance on the TBP show the main directions and the shares of the underground runoff. In the periods longer than two years, the greatest share of water from the karstic underground is discharged to the Soča, less to the Idrijca, and the least to the Vipava. The majority of the underground runoff gravitates westwards to the spring Mrzlek, which indicates the location and inclination of the impermeable basis (see Chapter 2.6) where the greatest part of basic runoff flows along the flysch depression into the Soča. 3.3. PRECIPITATION PROBLEMS IN RELATION TO WATER RUNOFF ON THE TRNOVSKI GOZD (J. PRISTOV) As the basis for the study of precipitation problems served the daily precipitation gauged at 07 hrs. From among 15 stations in the area of the Trnovski Gozd and the Nanos, only the station Podkraj is equipped with a gauge of Hellmann type which continuously registers the precipitation. Indeed, it is not enough for the analysis of precipitation situation because the distribution of precipitation in individual areas of the Nanos and the Trnovski Gozd considerably differs, from one precipitation situation to another. For the comparison of precipitation with discharges, the data from the following four hydrological gauging profiles in the area of the Trnovski Gozd and the Nanos and their rims were selected: the Idrijca-LP Podroteja the Vipava-LP Vipava the Hubelj-LP Ajdovščina the Lijak-LP Šmihel Analysis of the precipitation was performed on data from precipitation situations after the end of the long-lasting dry period in 1993. Heavy precipitation occurred on September 25, and were recurring until the end of October 1993. The precipitation situation between October 21 and 25, 1993 was studied in detail. The precipitation situation between October 21 and 25, 1993 The time and spatial distributions of precipitation were even over the entire area in this situation. The precipitation maximum occurred between Črni Vrh Nad Idrijo and Mrzla Rupa. This is the only case that the ratio of precipitation quantities was only 1:2 (Ozeljan 134 mm; Črni Vrh 265 mm). Podkraj received 206 mm of precipitation. This even distribution was possible due to more permanent precipitation without any longer interruptions. The precipitation in this case did not fall in the form of rainstorms. More abundant precipitation began in Podkraj on October 21, at 06 hrs, and by 09 hrs, 25 mm of precipitation fell; followed an interruption by 14 hrs, then followed more or less continuous precipitation by 01 hrs on October 23. Then, interruptions began to occur and precipitation completely ceased on October 24, at 15 hrs. The discharges at the gauging station Vipava reacted on the beginning of rather heavy precipitation with a 6-hour lag. A five-hour interruption of precipitation is almost unnoticeable on the diagram of discharges. The latter only began to lower some six hours after the end of precipitation. The precipitation, or, storms under 10 mm in short time are much blurred on the diagram of discharges, and there are no sharp extremes. Quite different are the discharges of the Hubelj. They react much faster on the precipitation than those of the Vipava, and also, any several-hour interruption is already manifested in the decrease of discharges. The lag of discharges behind the precipitation is 3 to 5 hours. The discharges of the Hubelj are lower by approx. one half than the discharges of the Vipava. There are two possible explanations: • that the precipitation catchment area of the Hubelj is much smaller, or, • that, at certain high water levels, the waters from this area reorient elsewhere. In this case, too, the spring Lijak behaves quite differently than the spring Hubelj or the Vipava springs. The increase, or the beginning of the increase of discharges lags behind the increase of the Vipava as much as 10 hours, and from the beginning of precipitation to the beginning of the Lijak discharge, as much as 16 hours. Also its hydrogram differs a lot. After the very fast increase of discharges, they amount to 10 - 14 mVsec as long as four days. However, the Lijak did not exceed this upper limit in the discussed case, and it only reached this value when the discharges of the Vipava, Hubelj and Idrijca already decreased a lot. This could somehow confirm the hypothesis that the Lijak lacks its own contributing area in the close proximity of the spring, but the water flows in from a more distant contributing area, and therefore, it is impossible to determine or delineate the area from which the Lijak is supplied. A quite different scene is offered by the discharges of the Idrijca at Podroteja which react much faster on the time distribution of precipitation. The beginning of the increase of discharges lags behind the beginning of precipitation by 9 hours, and at the following interruptions, i.e. during the already established high wave, these lags are only from 2 to 6 hours long. The ratio of discharges at the high wave approximates the following: Lijak - Hubelj - Vipava - Podroteja = 1:2:4:8, or it is shghtly higher. Determined in the described case of October 1993, were only the occurrence and duration of precipitation in the entire area, and the reaction of discharges on the precipitation at the following gauging profiles: Podroteja on the Idrijca, Vipava on the Vipava, Ajdovščina on the Hubelj, and Smihel on the Lijak. We tried to discover the time reaction of discharges on the precipitation; naturally, we had troubles in doing it since the entire area is rather well covered with a network of stations for daily gauging of precipitation heights, but very poor (only one gauging point, and even this one located at the eastern rims of the discussed area) in the continuous registration of precipitation. The crucial problem still remains; this is the co-ordination of the total quantity of precipitation with the discharges by individual precipitation situa- tions in the month of October 1993, and for the 1961-90 period. For these cases, the complex water balance analysis will be made. This problem is difficult because the gauged waters at the rims of the Trnovski Gozd and the Nanos do not represent the total quantity, because a part of the waters from this area drain underground towards the Soča (the Mrzlek spring). These quantities have not been determined so far, and it is very difficult to do it due to the reservoir of the Solkan hydropower plant. 3.4. CORRELATION AND SPECTRAL ANALYSIS (PH. MARTIN, J. KOGOVŠEK, M. PETRIČ, S. ŠEBELA, C. MARTIN) 3.4.1. Methodology The hydrodynamic functioning of the Hubelj and Vipava springs was studied also with the time series analysis - with correlation and spectral analysis (BOX & JENKINS 1976; JENKINS & WATTS 1968). For this purpose the STOCHASTOS programme, which was designed by MANGIN (1981a, 1981b, 1984) and written by D'HULST of the "Laboratoire Souterrain du CNRS" at Moulis (Ariege, France) was used. Presented results were obtained in a co-operative research of CNRS URA 903 (Aix-en-Provence, France) and Karst Research Institute ZRC SAZU (Postojna, Slovenia). This approach is based on the concept of the karst system (MANGIN 1975). We can define a karst system as an underground carbonate basin, which can however integrate unkarstified superficial sub-basins in the background. In this karst flows form the drainage network, which has in general a branching structure. Such karstic system is a place of dynamic processes, determined by inflows (precipitation and/or loss of water from rivers, CO^, etc.) and outflows (discharges, aqueous solutions and so on). The karstification efficiency must be defined as work capacity within the system, it means that in case of gravitational karst as a runoff product in regard to the altitude of gradient (the altitude difference between the inflow and outflow (spring) points). The heterogeneity of the area, the non-linearity of the flows and the contrast in hydraulic conductivity between the different parts of the aquifer (lURKIEWICZ & MANGIN 1994) are conductive to the adoption of the systemic and functional approach which is based on the study of the relations input - output. The use of correlation and spectral analysis necessitates time series of precipitation and discharges which are uninterrupted and of an identical duration. This approach first of all aims to describe the structure of time series (with random and periodical components, tendencies etc.), and then to establish the form of unit hydrogram and finally to draw attention to the multiple relationships between input and output. Graphs resulting from calculations made on each of the time series allow us to understand these structures. They are obtained using two initial choices: one is the maximum value of lag (m) which corresponds to the window of observation, the second, the step (k) corresponds to the amplitude of each change. The information of a duration less than 2k does not show up in the results. The correlogram shows how events are linked together for increasing intervals of time. High values indicate the presence of a tendency, low values suggest that events are not linked. A rapid decrease in the values of correlative coefficients indicate an absence of liaison at the end of a relatively short period of time. The size of interval corresponding to a value of the correlative coefficient of 0.2 is known as the "memory effect" (MANGIN 1984). The spectrum of density of variance which corresponds to a change in the variable (Fourier transform), expresses the components of the time series in the frequency domain. In order to avoid the possibihty that the results are biased, it is necessary to balance the calculations with an function such as that of Tukey or Parzen which are both very appropriate for use in hydrology (MANGIN 1984). The function of Tukey filters out less than that of Parzen. It is therefore preferable in the first approach since less information is lost. Nevertheless, it can allow artefactual peaks to appear. In order to alleviate any doubt a second calculation using Parzen filter can be used. High values for frequencies around zero indicate the existence of a tendency. By dividing the maximum value by two, we can obtain the "regulation time" which represents the duration of the impulse response. Each peak indicates the presence of periodical phenomena. The frequency from which the values become negligible is known as the truncation frequency (f). Beyond this, towards the higher frequencies, the spectrum only indicates the presence of white noise. The smaller the value of truncation frequency, the more the system is inert, which is to say less karstified. The cross-correlogram is calculated for the time series of precipitation and discharges. If the input signal is random, the cross-correlogram is a good image of the impulse response of the system, which is a good representation of the unit hydrogram. In the domain of frequencies, we reach on the one hand the amplitude function which estabUshes the relations between the input and output of the system, and on the other the phase function which for each frequency defines the phase lag between input and output. The phase lag (x) is defined with the equation T = 9/2Tcf. This information can be completed by calculating the functions of coherence and gain in frequency domain. The first expresses the linearity of the system. One non-hnearity often indicates that the output function is not uniformly determined by the input function which was used. The other, the function of gain, indicates phenomena of attenuation (value < 1) or amphfica-tion (value > 1) in the signal for each frequency. An attenuation in the higher frequencies is generally accompanied with an amplification of the lower frequencies. 3.4.2. Characteristics of the Used Data Basic hydrological characteristics of the studied karst area in the background of Vipava and Hubelj springs are presented in the previous chapters. Here we would just like to give some comments on the choice of the input function. For the purposes of this study, we selected the meteorological station at Otlica (820 m) which lies in the background of the Hubelj spring. An experience showed (MARTIN 1991 a, b) that it is useless to set up one rain-gauge station in a catchment area as rain is purely regional data that occurs at various places of the climatic micro-region as is Trnovski Gozd and Banjšice. For the Otlica meteorological station the average daily precipitation for the period 1985 - 1995 are 6.28 mm. The maximum daily value is 170.6 mm and for the interval of three days 230.6 mm. In four three-days periods the amount of precipitation exceeded 220 mm. The wettest month was October 1992 with 580.5 mm. We can conclude (Fig. 3.10) that the period with highest amount of precipitation is between October and December, and the second maximum is from April to May. Regarding the dry seasons the interval January - February is more significant than the period between July and August. The used data take account of the snow on the day of its fall, in a volume equivalent to that of meltwaters. In its natural environment, on the higher parts of the basin, the snow may last for several weeks. Based on the data gathered by the Hidrometeorološki Zavod RS, we counted for stations Otlica and Vojsko (1070 m) the number of days each year when the ground was covered by snow. From 1985 to 1995 the average number of days per year when the ground was covered with snow at Vojsko was 107. In 1985 the ground was covered for 166 days and in 1989 for only 49 days. At Otlica during the period of 1989 to 1995, the mean number of days when the ground was covered was 29 days with the maximum of 60 in 1995 (135 at Vojsko) and a minimum of 8 days. At the Postojna station (500 m), which lies further to the east, the ground was covered with snow for a period of 30 days in 1985; the snow represents 7 % of total precipitation. In 1991, the snow only accounted for 28 mm out of a total of 1681 mm. The volume of persistence of snow must be seen in terms of the mean altitude of the basins. This can be determined by conducting a study of '®0 concentrations (URBANC & PEZDIČ 1995). These would be 900 m for the Hubelj basin with a confidence interval of 750 m to 1000 m. And for Vipava basin the figure would be 850 m (with the confidence interval between 700 m and 950 m). -Vipava---Hubelj Otiica 16 E c (S > 06.08.91 05.08.94 05.08.95 Fig. 3.10: The data of precipitation (Otiica) and discharges (Vipava and Hubelj springs) in the period 1991-1995 smoothed with the moving average (window of 93 days). It appears that for medium and low altitudes like that of Postojna, the percentage of snow precipitation is negligible. For the Hubelj and Vipava backgrounds the persistence of a covering of snow over several weeks each winter causes delay between the moment when the precipitation are measured (meltwater for the measuring apparatus) and the moment when the snow covering melts. Because the duration cover varies according to the different altitudes, we might conclude that the recharge of the aquifers is retained and that constitutes a sort of support of the hydrological phases in spring. In this case it seems that the influence of snow is felt at the margin only and it almost does not affect the global statistical approach presented below. Yet it does not exclude the possibility that increase of snow cover is determining in some cycles. It would be convenient to divide the observed periods into those with particularly lot of snow or without it and make the comparisons. On the other hand, the evapotranspiration (on the base of Penman method the following values were calculated: 678 mm for the period 1959 -1979 (STAHL 1994), 637 mm for the year 1993 and 628 mm for 1994 (AVBELJ 1995)), which reaches about a third of the volume of precipitation during the year, reduces the available discharge with a maximum effect towards the end of spring and during the summer. 3.4.3. Analysis of Results and Comparative Study of Both Springs The daily data of precipitation on the meteorological station Otlica and discharges of Hubelj and Vipava springs, which were gathered by the Hidrometeorološki Zavod RS, were used in the analysis. The observation period was 11 years or 4017 days from 1 January 1985 to 31 December 1995. The correlation coefficient and the spectrum values were calculated with the use of step k = 1 and the maximum value of lag m = 125. Otlica---Hubelj Vipava 1 r(k) 0,8 0,6 0,4 0,2 -0,2 'a 25 50 75 100 125 Fig. 3.11: Correlogram of precipitation (Otlica station) and discharges (Hubelj and Vipava springs) for the period 1985-1995 (n=4017 days, k=l, m=125). The correlogram calculated according to the data of daily precipitation at Otlica (4017 days, average 6.2 mm, maximum 170.9 mm, minimum 0 mm, variance 244) shows an extremely rapid decrease in the values of correlative coefficients (Fig. 3.11). The value 0 was reached after 7 days. For the values of k > 3, only random fluctuations around 0 are persistently obtained. The interdependence of events is therefore very weak. It is nothing over 2-3 days which is the period corresponding to a chmatic episode or to the passage of one perturbance. The two other correlograms were calculated using data of average daily discharges of Vipava (average 6.5 m^/s, maximum 66 mVs, minimum 0.73 mVs; variance 69.9) and Hubelj springs (average 2.8 mVs, maximum 36 mVs, minimum 0.18 mVs; variance 15.2). These show an extremely rapid decrease in the values of the correlative coefficients with r = 0.2 for a very low value of k (Tab. 3.11). In these two cases the decrease is regular until r = 0.15 and k = 11. For higher k values, the correlative coefficients are always less than r = 0.15 and at k = 50 they reaches 0. Therefore there exists a statistical Fig. 3.12: Spectrum of precipitation (Otlica station) and discharges (Hubelj and Vipava springs) for the period 1985-1995 (n=4017 days, k=l, m=125) - calculated with the use of Tukey filter independence between the discharges which occur at about 12 days apart. We can conclude that the memory effect is considerably low, which would represent a small storage capacity and well developed karst drainage. Finally, let us note that the correlograms of the precipitation and discharges are very similar. The spectrum of precipitation shows low values for all frequencies and very low values for frequencies of more than 0.1 (Fig. 3.12). Such spectrum corresponds to a random character of the function of precipitation, even if two small peaks appear at the points when f = 0.008 and f = 0.052. The first of these corresponds to a periodicity of 125 days, the second to a periodicity of 20 days. Both peaks can be seen also on the spectrum calculated using Parzen filter (Fig. 3.13). Therefore we can reject the possibility of artefacts and a certain periodicity which shows characteristics of the Mediterranean climate can be defined. The value of the periodicity (125 days) corresponds to four months, which is more or less the duration of the two rainy periods (autumn and spring) which are separated by two dry periods (winter and summer) of about two months (Fig. 3.10). Otiica---Hubelj......Vipava 0,1 0,2 0,3 0,4 0,5 f Fig. 3.13: Spectrum of precipitation (Otiica station) and discharges (Hubelj and Vipava springs) for the period 1985-1995 (n=4017 days, k=l, m=125) - calculated with the use of Parzen filter With the use of Tukey filter (Fig. 3.12) also the spectrums of discharges for both springs were calculated. They show a very strong levelling out of frequencies of more than 0.1 and a disappearance of all information for frequencies of more than 0.25. The values obtained for f = 0 (23.8 for Vipava and 22.1 for Hubelj, and the regulation time of 12 and 11 days respectively) points to a levelling out of the higher frequencies and a consequent pronouncing of the lower frequencies. Besides this, the Hubelj spectrum shows a peak at the frequency 0.004 which corresponds to a periodicity of about 250 days. This feature is not found in the Vipava spectrum. The utilisation of the Parzen filter (Fig. 3.13) causes this peak to disappear. In this case we are witnessing an artefact which is probably linked to the periodicity of four months which become evident through the precipitation data. The resulting graphs show that the drainage of these two karst systems is well organised. A strong similarity (Fig. 3.14) is present in the cross-correlograms calculated using the precipitation occurring at Otlica and the discharges at Vipava and Hubelj springs (analyses of 4017 days). Both are tapered (the maximum ---Hubelj Vipava 1 r(k) 0,8 ^ 0,6 -0,4 -0,2 - -0,2 -125 125 Fig. 3.14: Cross-correlogram between precipitation (Otlica station) and discharges (Hubelj and Vipava springs) for the period 1985-1995 (n=4017 days, k=l, m=125). correlation coefficient for Vipava springs is 0.62 and for Hubelj springs 0.70) and descend after only 10 days to a very low r value (0.02 and 0.03). For greater intervals, the fluctuations are slight and random. The part corresponding to negative values of k also shows random fluctuations around 0. However, at similar analyses conducted on binary karst higher values of r for the negative values of k were observed. This characteristic doesn't indicate that the discharges precede precipitation (which has no sense), but that the input signal is not random. We know that the Vipava springs are partly recharged by the surface rivers, yet in the cross-correlogram the values of r are very low for the negative values of k. This indicates that the portion of the river recharge is very low and/or that the time series of river discharges have a structure similar to the one of the precipitation. The function of precipitation is therefore random and each cross-correlogram constitutes a good image of the impulse response of the studied karst system and thus a good representation of its unit hydrogram. These cross-correlograms thus point to the existence of functional drainage structures which are capable of the rapid transferral of rainwater or meltwaters to the springs. In this case, these structures can only be karstic networks with shafts, galleries, etc. Two obtained amplitude functions are very similar (Fig. 3.15) with positive values for all frequencies and larger values for f < 0.1. The curve for the Vipava springs is more smooth than the curve for the Hubelj spring. The existing functions within the frequencies of relations between inflow and outflow of the system must not be zero because otherwise other functions (phase, coherence, gain) cannot be interpreted as, when the relations are missed it is obviously impossible to study their properties. The zone of relation input-output or the zone of exchange is between f = 0 and f = 0.168. The small peaks correspond with periodicity. On both curves we can identify the peak at f = 0.056, which represents the period of 18 days. This periodicity is similar to periodicity, which was defined in the spectrum of precipitation for f = 0.052. For basic frequencies the peak for Vipava-curve is at f = 0.008 (125 days), and for Hubelj-curve at f = 0.012 (83 days). These two curves indicates the importance of phenomena of basic and middle frequencies on the relation precipitation - discharge. The phase lag is 7 days for the Hubelj spring and 8 days for the Vipava springs (Tab. 3.11). Calculated for the boundary frequency of the zone of exchange (f = 0.168) the phase lag for the first spring is '/2 day and for the second 1 day. In the zone of exchange the coherence functions ranges between 0.75 and 0.95. These values indicate good linearity of the system for basic frequencies, which essentially reflect the general functioning of the system. The gain functions show amplificated values for periods greater than 16 or 17 days. For other frequencies the values are attenuated. The maximal amplification for the lowest frequencies is limited. o I Ph cr J iT- - L-.-1- . -» - v s 2 t/D oo o' DJ I Ü « 20 40 60 60 100 120 140 160 laO 200 220 240 260 280 300 320 340 360 days 2 4 6 8 10 12 14 16 16 20 22 24 26 28 30 frequency P MQ = 3J = = 3.03 m ' / s 0.23Tn»(s Fig. 3.19: Abscissa averaged discharge frequency diagram of Hubelj springs for the years 1961 to 1990. • The factor of minimum to maximum discharge at the Vipava springs equals to 1:100 while this factor equals to 1:267 at the Hubelj springs. • At the Vipava springs the Q,^^ accounts to approximately 1/7 of the MQ while at the Hubelj springs the Q^^ accounts to approximately 1/13 of the MQ. • The MQ at Vipava spring accounts to 1/10 of its highest discharge. At the Hubelj springs this accounts to 1/16. • Very high discharges occur more frequently at the Vipava springs than at the Hubelj springs. • Low discharges occur with similar frequencies at both springs. However, the range of low discharges at the Vipava springs is broader. At the Hubelj springs the low discharges occur with more changing frequencies. The thirty year's time series were also interpreted using an autocorrelation analysis. An "investigation of sequential properties of a series by autocorrelation is already classical statistical technique. It is used to determine the linear dependence among successive values of a series that are a given lag k apart" (YEVJEVICH 1972). As the measure for the linear dependence between the two values the autocorrelation coefficient, rk is used. The equation used for the analysis corresponds to the form proposed by Jenkins and Watts and used by (MANGIN 1984) during his analysis of three karstic flow regimes in the Pyrenees. The open-series approach was used for Vipava Hubei; J I 6me-lag. k (daysl Fig. 3.20: Autocorrelation functions with time-lags 1 to 809 of Vipava und Hubelj discharges. As basis for the 30 year's time series was used. the analysis since according to (YEVJEVICH 1972) it is not advisable to use a circular-series approach because the first and the last part of the series might be independent. In Fig. 3.20 the results for the autocorrelation using a time lag from 1 to 80 is shown. Fig. 3.21 represents the autocorrelation functions with time-lags from 1 to 3650. The autocorrelation curves of the Vipava and Hubelj springs, considering a time lag k = 1 to 80 days, are very similar. They both show that the "memories" of the springs are bad, i.e. that the discharge depends only little on the discharge of the previous two to five days and that it is practically independent from the discharge of six or more days ago. However, Vipava shows a slightly higher k=l autocorrelation coefficient than Hubelj. For the successive time lags the autocorrelation coefficient of Vipava drops faster. This means that the discharge of the Vipava springs is slightly higher influenced by the discharge of the previous day than in the case of Hubelj springs, while the memory of the Hubelj springs improves in comparison to the Vipava springs from the third day onwards. The autocorrelation diagram for the Vipava and Hubelj springs with a time-lag, k=l to 3650 shows once more that the correlation coefficients drop very fast during the first few k's. Thereafter they fluctuate sinusoidally around the zero-line. Though their amplitudes reach only a rk of 0.08, the form of the correlation curve is interesting. It can be observed that the correlation coefficient £ i £ I < 1 VicSMS Kubaq ^V V; V v^ V UM — 0.7a 0.60 «.aa 0.» ■ o.to TOSS ;5ZS 21» örtiö-iag. k (ia/s) zsss > 32W 1 i i s) o 0 = s 1 s I < I tr^ .fl-tD Fig. 3.21: Autocorrelation functions with time-lags 1 to 3650 of Vipava and Hubelj discharges. As basis for the 30 year's time series was used. fluctuates with a period of exactly one year (both curves). This means that the yearly discharge values are correlated. Hence it can be supposed that the daily discharges do have a deterministic component and are not exclusively aleatory. It is conspicuous that the Vipava springs autocorrelation curve fluctuates very little and that the Hubelj autocorrelation curve fluctuates, obviously, not only with a yearly period but also with a half-yearly period. The half-yearly amplitude though is less than for the yearly fluctuation. It actually means that the discharges of at least Hubelj springs are also correlated on a half-yearly basis, i.e.there is some sort of a relationship between the discharge today and half a year later. Furthermore the mean discharge curves for the Vipava and the Hubelj springs were evaluated. Bases for the curves were once more the 30 years daily discharge data of the period 1961 to 1990. To emphasise on the course throughout the year a regression of the 10th grade was fitted. Additionally the 30 days running mean was calculated and plotted. The daily mean discharge curves are presented in Fig. 3.22 and Fig. 3.23. It is striking that the courses of the mean discharge curves of the two springs are identical. They both show minima in July/August and maxima in spring and autumn. 4) pi Vtpava averaged 196M990 1 I .-iif.. i^tVi I iVrfi ■ ifpfi I .vy, nfyrii. i-*."!'!, .fai, .f.^, ■ , |Rttj ■ 0 20 40 60 so 100 120 140160 730200220240260280300320340360 days 1 1 r Fig. 3.22: Daily mean discharge curves of Vipava and Hubelj springs' for the period 1961 to 1990. To emphasize the course a regression of the iO"" grade was fitted (thin line) and the 30 days running mean plotted (bold line). These mean discharge curves should furthermore be compared with the mean precipitation curve shown in Fig. 3.23. The following is conspicuous: • When the main precipitation occurs, i.e. in June, the mean discharge curve drops. This might be due to the high evapotranspiration in summer. • The increase of precipitation after the precipitation minimum in July causes an increase in the mean discharge with a delay of approximately one month. • Though the precipitation amount drops during the winter months, the mean discharge rises to a second peak in spring. This could be due to the snow melt, i.e. water which was stored as snow comes to a discharge. It appears though, that the amount of precipitation fallen during the autumn and winter times is too little to produce: 1. the rising mean discharge during winter time caused by rain and 2. the rising mean discharge in spring caused by the snow melt. This can only be explained by too little precipitation measured in this period of the year. As reported by IVANCIC (1995) the Hydrometeorological Institute Ljubljana estimates the error due to wind influences during the measurements of snowfall to 50 %. This could explain where the lacking precipitation volume comes from. 12 g '5. o S Q. 11 10 9 ^ 8 ^ 7 6 ^ 5 4 ^ 3 -E Z 1 -Ž data base: 1978 -1990 —slalion 083 —stalior 102 —station 143 1 I 1 i I I I ^ \ I I—r Jan, Feb. Mar. Apr. May. Jun. Jul. Aug. Sep. Oct. Ntw. Dec. months Fig. 3.23: Monthly mean precipitations as percentages of the annual mean presented for the stations 83, 102, 143. Data base is the period 1978 to 1990. 3.5.2. The Recession Curve Analysis For both springs, the Hubelj and the Vipava springs a recession curve analysis was carried out based on the discharge data of the month July to October of the years 1961 to 1990. Aim of the analysis was to develop a master recession curve for each of the two springs. The recession curve analysis dates back as far as 1905 when Maillet defined an analytical expression for recession curves of long-lasting dry periods (equation (3)): Q = Q)exp(-at) (3) where Q^ is the discharge at time t; Q^ is the previous discharge; t is the time elapsed between Q^ and Q^ and a is the recession coefficient of dimension T' (FORD & WILLIAMS 1989). Though this expression was actually designed for recession curves of porous aquifers it is widely used in karst hydrology, i.e under non-homogeneous and non-isotrope conditions. BONACCI (1987) as well as FORD & WILLIAMS (1989) have provided detailed reviews on the use of recession curves in karst aquifer analysis. If the curve of the equation (3) is plotted semi-logarithmic (Q on the logarithmic ordinate) it is represented by a straight line with the slope - a. According to MARTIN (1973) a better concept to be used in hydrology is the use of the half-life of the discharge. The half-life t^^^j corresponds to the time needed that the discharge is reduced by 50 %. The half-life corresponds to: t().5 = ln(l/2)/ln(exp-a) (4) According to MILANOVIČ (1976) the emptying of a karst aquifer is frequently characterised by recession curves that may be fitted by several short, straight lines, each being characterised by a different slope, hence having different recession coefficients (a^j, a^^, ...., a^^). This type of recession curves reflect the complex hydrogeological characteristics of karstified rocks. Assuming the theory of the linear reservoir this complex recession curve can be mathematically expressed as: Qi = Qoi exp(-aoit) -F Q02 exp(-ao2t)-l-......-l-Q» exp(-cx„t) (5) MILANOVIČ (1976) also states that under the conditions of a well-developed karst system, three recession coefficients may usually be expected a good fit. The greatest reflects the rapid outflow of caves and channels, the medium the outflow of well integrated karstified fissures and the smallest the drainage from pores and narrow fissures. BONACCI (1993) states that different segments of the recession curve might not only reflect a decrease in effective porosity but may also be a result of a decrease in the catchment area. He showed a such caused decrease due to the decrease of the underground hydrogeological catchment area at three springs down the Neretva river in the Dinaric karst (BONACCI 1993). The aim of recession curve analysis is to derive a characteristic recession of a particular discharge region. One of the problems most often encountered during such an analysis is the high variability encountered in the recession behaviour of individual segments. A physically based short-term or seasonal variation in the recession behaviour adds to the problem of deriving a characteristic recession (TALLAKSEN 1995). According to TALLAKSEN (1995) the master recession methods try to overcome the problem by constructing a mean recession curve. This is then known as the master depletion curve. All the information on variability is lost in this type of curve. There exist several methods of deriving a master recession curve. (McCUEN 1989) describes simple procedures to derive the master depletion curve. One, the analysis of covariance method, is described by BAKO & OWOADE (1988) for a field application. BONACCI (1993) states that in karst areas the last section of the recession curve (on semi-logarithmic presentation) actually represents the master depletion curve. He furthermore concludes that this latter section of the recession curve is significant and that its function is to define and predict the behaviour of the remaining groundwater reserves during drought periods. (U PS '8:8- 8.0 - 7.0 - 6.0 - 5.0 - 4.0 - 3.0 - 20 - ir 0.8 0.7 0.6 0 5 0.4 0.3 -02 1 —•— mean median master depletion curves Oj mean: 0.0257 d ' a^ median: 0.0162 d" I I I I I I I I 20 I I I I I I 30 days ~t I I I I r~ 50 Fig. 3.24: Mean and median recession curves for Vipava, obtained by the results generated by the program FIEBEL assuming a starting discharge for reservoir 1 of 10 mVs. 8.0 - 7.0 - 60 - 6.0 - <0 - 2» (D JC •a 1.0 - 0.9 0.8 0.7 0.6 0.5 0.2 ^ — mean median Qoj master depletion curves y a, mean; 0.0477 d' Oj median: 0.0278 d"' "■•■o 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 I 1 I 1 1 1 L 1 1 2.45 1.35 1.01 0.66 20 30 days 60 Fig. 3.25: Mean and median recession curves for Hubelj, obtained by the results generated by the program FIEBEL assuming a starting discharge of 10 m^js for the first reservoir. The master depletion curve was determined on the basis of long term valuations of recession parameters. For this purpose an objective programme, called FEIBEL was used (SCHUMANN 1995). It automatically selects the recession branches to be used for the analysis according to the following criteria: 1. They have to begin underneath the mean discharge and have a length of at least 8 days. 2. The discharge values need to reduce continuously (error limit being 5%) 3. The second discharge value of a beginning recession branch needs to be really smaller than the first one (i.e. the error hmit is only valid from the third discharge value onwards). Since using this method one gets for each recession branch considered one a-value, out of these one representative a-value needs to be calculated. This has been done by using the mean and the median values. The results of the recession curve analysis are shown in Tab. 3.12 (Vipava) and Tab. 3.13 (Hubelj) as well as in Fig. 3.24 (Vipava) and Fig. 3.25 (Hubelj). Tab. 3.12: Results obtained for the spring Vipava, using the program FEIBEL. no. of branch es a range of a mean startin gQ half life [days] volume mean «1 3 0.7951 0.6288 ? 0.9 - 0.2 113 0.4164 1.1895 3.71 1.7 - as 164 0.0257 0.1835 1.97 27.0 6.62 * 10® median ai 36 0.8605 1.4291 ? 0.8 - «2 146 0.2595 0.8607 2.30 2.7 - «3 164 0.0162 0.1835 1.70 42.8 9.07* 10® Tab. 3.13: Results obtained for the spring Hubelj, using the program FEIBEL no. of branch es a range of a mean startin gQ half life [days] volume [m^] mean «1 10 0.7944 1.1609 ? 0.9 - Oil 93 0.4360 1.1895 2.45 1.6 - «3 167 0.0477 0.2834 1.01 14.5 1.80* 10® median tti 28 0.6253 1.0785 ? 1.1 ai 134 0.3287 0.7463 1.35 2.1 «3 167 0.0278 0.2834 0.66 24.9 2.05* 10® Both tables Tab. 3.12 and Tab. 3.13 show for each reservoir the number of branches used for the calculations, the calculated a-values, the range of the occurring a-values, the mean starting discharge of the recession branches, the half-life according to the a-value and the volume of groundwater left above the spring water level when the reservoir begins to empty. The volume was only calculated for the third recession branch as the calculation of the volume presumes diffuse flow. This is only valid during the low flow period i.e. when the last reservoir is exclusively discharging. The tables do not allow a conclusion which calculation procedure (mean or median) is the better one. However, it can be stated that range of a decreases for the second and first reservoir when the median is used to determine the representative a. Furthermore a higher number of branches are left to calculate the recession coefficients of the second and first reservoir as the values for the representative a and mean starting discharge are lower when using the median as the representative recession values. From the statistical point of view the median value is to be preferred, hydrologically though it can not be decided which value is the more appropriate. It is striking that the volume of water left above the spring water level in the aquifer of Vipava is about four times larger than the volume of the water left in the aquifer of the Hubelj springs. This could be due to: • A higher effective porosity in the Nanos karst aquifer than in the Trnovski Gozd karst aquifer. • A greater thickness of the high water stand zone above the spring water table in the Vipava springs aquifer than in the Hubelj springs aquifer. • A greater 'surface area' of the high water stand zone of the Vipava springs aquifer than the Hubelj springs aquifer. Fig. 3.24 and Fig 3.25 show the results obtained in a graphical form. The starting discharge of 10 mVs for the first reservoir is assumed to visualise the situation. The lowest discharges correspond to the springs' minimum discharges of the period 1961 to 1990. They primarily show that for the first and second reservoirs of the spring groups do not exist remarkable differences when considering the ranges of the occurring a-values. The recession coefficients of the two reservoirs are alike, hence their half-lives. A statement to the first reservoir should anyway be made very carefully as the number of recession branches left over for the analysis, (using the mean values) was with 3 and 10 very low. But still it might be stated that the median recession coefficients are alike. A difference in the mean starting discharges can be noted. For the Vipava springs the mean starting discharge (of the mean and median calculation procedure) of the second reservoir (i.e. when the first reservoir stops emptying and the second reservoir becomes the dominating one) is about 1 mVs higher than for the Hubelj springs. A different situation can be observed for the outflow of the third reservoir. The mean starting discharge for the exclusive outflow of this reservoir, which corresponds to the base flow generating reservoir is about 1 mVs lower at the Hubelj springs than at the Vipava springs. This is about the same situation as for the second reservoir. In both cases this correspond to approximately 2/7 of their MQ's. The recession coefficients, however, for these third reservoirs are remarkably different for the two spring groups Vipava and Hubelj. The Vipava recession coefficients (mean and median values) are close to half of the Hubelj springs recession coefficients. Hence the half-life for the Vipava springs is about double the half-life of the Hubelj-springs. Assuming that these master depletion curves are exclusively a result of diffuse flow this situation allows two possible interpretations: • The hydraulic gradient at the Vipava springs is smaller than at the Hubelj springs. • The permeability of the aquifer discharged by the Vipava springs is smaller than the permeabihty of the aquifer discharging the Hubelj springs. A very high hydraulic gradient of the underground water behind the Hubelj springs is confirmed by (HABIČ 1985 as quoted in JANEŽ 1994) but no explicit statement has been made on the hydraulic gradient of the underground water behind the Vipava springs. 3.6. THE ELECTRICAL CONDUCTIVITY AS INDICATOR FOR HYDRODYNAMIC PROCESSES IN THE VIPAVA SYSTEM (T HARUM, H. STADLER, N. TRIŠIČ) 3.6.1. Measuring Equipment In Vipava dataloggers were installed at the spring 4/7 (water level, electrical conductivity and temperature), 4/3 (conductivity and temperature) and at the gauging station for total runoff (4/8, conductivity and temperature). The discharge of the Vipava springs is being measured at two gauging stations: springs 6-4/7 and total runoff 4/8. Therefore it is only possible to separate two groups concerning the discharge of the 4/7 main outlets. The group of the springs 4/1 to 4/5 can be calculated as the difference between the total discharge of no. 4/8 and the measured discharge of the springs no 4/6 and 4/7 (compare Chapter 4, Fig. 4.12). The conductivities are compensated to 25° C, temperature effects can be neglected. The dataloggers measured every 5 minutes and stored an average value every 15 minutes. The gauging station no. 4/8 is being equipped with a water level recorder by HMZ Ljubljana, long-time series from 1960 - 1995 are available. 3.6.2. Suppositions and Methodological Aspects The discharge of karstic spring consists of different components with different residence times in the aquifer. Usually it can be separated into two components, which are termed base flow and direct flow corresponding to their different residence time and flow behaviour. The direct flow component represents the portion of water infiltrated from precipitation, which flows directly with short retardation through the main channels in the karst system to the spring. The base flow component consists of water stored in microfis-sured zones of the the aquifer over a longer time. The conventional hydrograph separation procedures using the exponential function after MAILLET (1905) and extrapolating this depletion function back under the peak of the total hydrograph allow an approximate separation of the two components base flow and direct flow (s. Chapter 3.5). This method gives only information about the hydraulic behaviour of the aquifer (MÜLLER & ZÖTL 1980; BEHRENS et al. 1992). The volumes of reservoir water calculated are corresponding to the volume of mobile water, not including temporarily stagnant water, i.e. water, which can only be discharged by hydrauhe stimulation under increasing hydrauhe head. Contrary the measurement of natural tracers as stable isotopes and chemical parameters of input and output gives the possibility of estimating the portions of older reservoir water and event water discharged at the spring and provides information about the mixing and solute transport processes in the aquifer. The water volumes calculated by means of natural tracers include the volume of temporarily stagnant water in the system and are not directly comparable with the volumes of direct and base flow components computed by the classical hydraulic separation method. For hydrogeological investigations it has to be emphasised to include both methods due to their complementary information about the aquifer characteristics. Therefore and contrary to the assumptions in Chapter 3.5. and according to previous investigations of the ATH-group in Karst aquifers of the Swiss Jura (MÜLLER et al. 1980) and of the Lurbach system (BEHRENS et al. 1992) it is important to emphasise the difference between "older" reservoir water ^ base flow and event water ^ direct flow. Assuming the existence of only two discharge components, they can be separated combining the simple mixing equations Qt = QE + QR (6) and Qx * Qh * c, + Qr * c, (7) to Qk= QT * (C, - q)/(C, - C,) (8) where Q-^, = Total discharge at the spring in 1/s Q,^ = "Older" reservoir water in 1/s Q^ = Event water component in 1/s Cj^, Cjj = Corresponding tracer concentrations The following suppositions have to be taken into account (HARUM & FANK 1992): 1. Sudden input of event water into the aquifer. 2. Significant differences in the contents in input and output. 3. No physical, chemical or biological reactions of the tracer during the transport in the aquifer. 4. Negligible or well known fluctuations in the background concentrations. 5. Exact measuring of discharge and tracer concentration. 6. Especially in karst systems as the Vipava aquifer sufficiently short interval of the measurements. For most of the "ideal" tracers as the stable isotopes "^O, -^H and some chemical parameters as i.e. Mg++, NO," and SO^" the exact determination of the time-concentration curves is hindered due to economic problems (especially in karstic regions with a quick response of discharge to precipitation events short sampling interval are necessary causing a high amount of expansive analyses). The electrical conductivity represents only a measure for the total mineralization, but it is has the big advantage that it can be measured on-line with relatively high accuracy. The disadvantage is that the dilution of certain chemical parameters due to the lower mineralised precipitation water is overlaid by increasing concentrations of other ions due to processes of out-washing of dunging substances and solution during the passage of the infiltrated precipitation water through the unsaturated zone (BEHRENS ET AL. 1992; HARUM et al. 1990; HARUM & FANK 1992; KENNEDY et al. 1986). Therefore the electrical conductivity cannot be considered as an ideal tracer, but the the analysis of the exactly recorded time series of discharge and conductivity can give approximate ideas of the processes of solute transport and mixing in the aquifer during the underground passage. Assuming that a part of infiltrated water is flowing directly without greater retardation and without processes of solution through karst channels to the outlets, the conductivity can be used for an estimation of the portion of this quick flow component (called event water) on the discharge of the springs and allows a relative comparison of the hydrodynamic behaviour of springs. 3.6.3. Separation of the discharge components 3.6.3.1. Analysis of long-term fluctuations of the runofl" year 1995 For the year 1995 discharge and conductivity data exist for the springs Vipava 4/6 - 4/7, 4/8 (total discharge) and partly 4/3. The discharge of the spring group 4/1-4/5 can be calculated by the difference between Vipava 4/8 and 4/6-4/7. For the analysis of the data mean daily values of discharge and conductivity were used. The first step is a comparative analysis of the different springs. In Fig. 3.26 the weighted means over 30 days are plotted compared to the weighted discharges. It is clearly visible that the total discharge Vipava 4/8 and spring 4/3 have nearly the same fluctuations of conductivity, whereas the graph of Vipava 4/7 shows significant differences which are probably due to the partly different recharge area (mixing with karst water coming from the Bela creek (sinkhole downstream of the village of Sanabor) as indicated also by the results of the tracer experiment). The similarity of the EC-fluctuations of total discharge (4/8) and spring 4/3 indicate that the springs group 4/1-4/5, which represents the greatest part of the total discharge at the gauging station have nearly the same regime. This conclusion is also confirmed by the results of the tracing experiment and short-term conductivity measurements by data loggers at the other springs. Therefore the EC-values of spring 4/3 (no measurable discharge) are assumed to be representative for the group 4/1-4/5. It is visible in Fig. 3.26 that the EC-curve measured at the total discharge shows sometimes stronger dilution effects. This effect can be explained by a 96.01-01 95.01-51 SS-Oa^ 95-04.02 9S.06.02 «-07-02 9&08-01 95-08-01 95-1frfl1 95-11-01 95-li01 Fig. 3.26: Weighted means over 30 days of discharge and electrical conductivity of the Vipava springs 4/3 (representative for the group 411-415), 417 and the total runoff at the gauging station (418). certain portion of surface water originating from local precipitation events in the village of Vipava (water from roofs and streets) which is situated upstream of the gauging station. For the long-term analysis of the different discharge components it has to be taken into account that the background conductivity CB of the longer stored reservoir water in a karst aquifer has seasonal variations which have to be included in the mixing equation mentioned above. Therefore it was assumed, that the highest monthly conductivity values are representative for the "older" reservoir component. The input concentration CE was assumed to be constant with a mean conductivity of CE = 30 yU-S/cm 25 °C. Variations of it of ± 10 jiS/cm give no significant differences in the results. From spring 4/3 only conductivity data from the first 6 months of the year 1995 exist. But a correlation analysis of the measured total discharges QT and computed reservoir discharges QR indicated a strong hnear relation between both parameters. Therefore and for the reason of a comparison of the results of one annual runoff period the missing values could be estimated with sufficient accuracy using the linear regression equation in Fig. 3.27. The results of calculations are plotted in Fig. 3.28 (total discharge Vipava 4/8), Fig. 3.29 (Vipava 4/6-4/7) and Fig. 3.30 (Vipava 4/1-4/5). All values are daily means except the background conductivity of the "older" reservoir water (highest monthly values). The discharge hydrographs are plotted in comparison to the event water component computed by the mixing equation. S 01 a Vipsrvatn: QB = 0.7879Qr +687.59 R= = 0.973 Vipava 4«-4/7: 08 = 0.79530,1-222.8« = 0.9818 Vipava 411-iB: Qr = 0.8S26QT + 2S6.87 R' = 0.9919 Vipava 4/1-4/5 Vipava 4/6-4/7 4/8 ♦ VIPAVA 8 AVIPAVA6-7 □ VIPAVA 1-5 0 5000 10000 15000 20000 25000 30000 35000 40000 45000 50000 Qt (1/s) Fig. 3.27: Relation total discharge Q^. to reservoir component Q^ for the Vipava springs. The results indicate for all springs that during flood events the greatest portion of discharge consists of "older" reservoir water. The portions of "young" event water, which are plotted in Fig. 3.31, reach maximum 27 % at the springs and 36 % at the gauging station Vipava 4/8, where surface water from roofs and streets in the village of Vipava is drained to the Vipava river. The mean annual portion of event water of the total discharge is only in the range of 10 % for the springs and 12 % at the gauging station including 95-01-01 95-01-31 95-03-02 95-04-02 95-05-02 95-06-02 95-07-02 95-08-01 95-09-01 95-10-01 95-11-01 95-12-01 Fig. 3.28: Mean daily values of discharge Q, event water component Q^, electrical conductivity EC and estimated background conductivity EC,^^^^ at the total outflow of the Vipava springs (gauging station Vipava 4/8) for the year 1995. 95-01-01 95-01-31 95-03-02 95-04-02 95-05-02 95-06-02 95-07-02 95-08-01 95-09-01 95-10-01 95-11-01 95-12-01 Fig 3.29: Mean daily values of discharge Q, event water component Q^, electrical conductivity EC and estimated background conductivity EC^^^^ at the spring Vipava 417 (discharge = Vipava 416 - 4/7) ) for the year 1995. surface water. At higher discharges the spring group 4/1-4/5 seems to have a higher portion of "older" reservoir water, a fact, which is probably due to the greater distance of permanently active sinkholes. These results agree well with those of the isotope investigations (Chapter 5.), where the portion of event water on the discharge of the Vipava springs was calculated as 21 % for selected single events. 45000 40000 35000 30000 25000 a 20000 15000 10000 5000 EC4 1 /V EC —j— - I 1 0 1 ill 1 u^J Jw K A 1 1 n 350 300 250 200 150 100 - 50 0 1/1/95 31/1/95 2/3/95 2/4/95 2/5/95 2/6/95 2/7/95 1/8/95 1/9/95 1/10/95 1/11/95 1/12/95 Fig. 3.30: Mean daily values of discharge Q, event water component electrical conductivity EC and estimated background conductivity EC^^^^^ at the springs Vipava 411-415 (EC measured at Vipava 413) for the year 1995. The event water components Q^ from June to December 1995 where calculated using the linear regression equation in fig. 3.27. 40,00 0,00 95^1-01 9501-31 95K»o o O O o o -i v ^ ^ 20 30 40 DlscUsrge (itiS/B) ■ Ca - Vipava □ Ca - HuM| • Mg - Vipava « Mg - Hubgll o Ca - VIpava^ivBve + Mg -Vlpava^nva Fig. 4.4: Relationship between the spring discharge and the calcium and magnesium levels of the springs Hubelj and Vipava for the monthly measurements and for various water pulses. tions in the Hotešk and Mrzlek (excluding the measurements when this water is mixed with the Soča water) may be compared to that of the Podroteja; the variations in the Vipava are higher, and still higher again in the Prelesje. Considerably higher values of the Vipava ratio compared to the Belščica indicate the latter's insignificant share to the Vipava springs. The highest Ca/Mg ratio (average value 26) with greatest variations during the year was recorded in Kajža. The faults between Banjški and Avški fault are hydrogeologically very important for this spring. The spring reacts to rainfall very quickly (JANEŽ & ČAR 1990), and it explains considerable variations in Ca/Mg ratio. At monthly samphng the comparison of Ca and Mg level related to discharge indicated that Ca level in the Vipava decreases by the increase of discharge (up to 10 mVs); also the analyses of water pulse, however in smaller extent, indicated the same (Fig. 4.4). But the seasonal variations in hardness are felt; the lowest hardness appears in late winter and in spring. The Ca level in Hubelj varies slightly more without an obvious trend, while the Mg level decreases slightly when discharge is increasing. In the Vipava this was not perceived, neither at monthly samphng nor in the water pulse when we have taken the samples during higher water level during monthly sampling. The total hardness of all the springs varies from 2.4 to 4.2 meq/1. Total hardness of Hotešk, Kajža and Korentan varies seasonally while these oscillations are less prominent at other springs. A similar picture is displayed by specific electric conductivity and carbonates content. The highest value of total hardness was recorded in Prelesje, followed by Korentan, Podroteja, Kajža, Vipava and Hotešk, while Mrzlek and Hubelj had the lowest values. Total 19.08. 27.11. 1993 07.03. 15.06. 23.09. 1994" 01.01. 11.04. 20.07. 1995 —CwbOfiBtes Hubelj -0-Ca»M8 HuMj -♦^CarDonate» Vipava -«-C«<-M8 Vipava Fig. 4.5: Variations of the total hardness and the carbonate contents in the springs Hubelj and Vipava during the observation period (monthly samples). hardness of Prelesje, Korentan and the Vipava oscillate the most, within an interval of 1 meq/1. They are followed by Podroteja, Kajža, Hotešk, Mrzlek and Hubelj, the latter oscillating the least, within an interval of 0.5 meq/1. Fig. 4.5 shows rather constant level of carbonates and total hardness in the Vipava and Hubelj. 4.1.1.3. Chloride, nitrate, sulfate, sodium and potassium In the monthly samples the levels of chloride, nitrate, sulfate, sodium and potassium were also recorded. Over a two years period in all the springs and in the Bela and Soča the level of chloride was up to 4 mg Cl/l. The only deviation was recorded in the Belščica; it increased up to 8 mg C171, and once even to 12 mg Cl/l, indicating the human impact on its superficial flow to the swallow-hole. The levels of nitrate in the Hotešk, Kajža and Soča never rose beyond 5 mg NOj'/l. Their average value is between 3.1 in 3.6 mg NO3VI. Slightly higher values were recorded in Mrzlek, Korentan, Bela and Prelesje with average values between 3.9 do 4.3 mg NO^Vl • The highest values were recorded in the Hubelj, Podroteja, Belščica and Vipava with average values from 5.7 to 6.5 mg NOj'/l. In Vipava the values varied between 4.3 and 10 mg no3/I, in Belščica between 4.4 and 7.5 mg NO^Vl. Actually, in the Vipava slightly higher values of nitrate levels were recorded than in the Belščica. The variations of the nitrate levels during these two years were observed, yet there is no evident mutual connection. Probably the more distinctive pollution is due to nitrates, but also chlorides and sulfates appear during the initial time of a water pulse. The lowest sulfate level was recorded in Kajža (average value 6.8 mg SO/-/1 ), followed by Podroteja, Mrzlek and Hotešk being up to 9 mg SO//1; the Vipava, Korentan and Soča had up to 11 mg SO^^/1. Higher values were recorded in the Belščica, and in particular in Prelesje and the Bela where up to 18 mg SO^^/l were measured. The lowest levels of Na were recorded at Hubelj, Mrzlek, Podroteja, Soča and Kajža (up to 1,7 mg/1). They are followed by Hotešk, Prelesje and Korentan with maximal values up to 2.9 mg/1 and Vipava with values in an interval from 0.9 to 3.1 mg/1. The highest values were measured in the Bela and Belščica. In the Bela up to 4.8 mg/1 and in the Belščica up to 7.2 mg/1. Hubelj, Podroteja, Mrzlek, Hotešk and Kajža contain less than 0.5 mg/1 of potassium. The Vipava and Soča contained up to 0.7 mg K+/1, Korentan and Prelesje up to 1.3 or 1.6 mg/l; the highest values were measured in the Belščica (1.9 mg/1) and Bela (2.4 mg/1). 4.1.2. Monthly observations of the precipitation (M. ZUPAN) The monthly precipitation sampling started in December 1992 at the four meteorological stations Vojsko, Trnovo, Podkraj and Bilje (changed in January 1995 by Slap). In April 1993 Lokve and Postojna were added. The samphng on Trnovo was stopped in July 1994 from technical reasons. The main purpose of the precipitation sampling was to provide the samples for isotope analyses. However we wanted to get some information about the physical and chemical composition of precipitation as well. The samphng was carried out by Bergerhoff (VDI 1972) samplers. In the precipitation samples we analyzed the same parameters than in the spring water samples. The same methods were used (chapter 2.5) and the same control criteria (chapter 4.1.2) than for spring water analysis. The data analysis showed some seasonal trends in some of the sampling points. However, we decided the meteorological data should be taken in to the consideration. Unfortunately it could not be done in the short period of time we had. 4.1.3. Weekly sampling in the springs Hubelj and Vipava (M. ZUPAN) In weekly samples we measured pH value, conductivity, calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), bicarbonate, nitrate, chloride and sulfate. The methods used are described in chapter 2.5 (Water Quality). All measured data were controlled by conductivity (measured and calculated) and ion difference. The permissible value of the coefficient between calculated and measured conductivity 0.9 - 1.1 was taken in to account (GREENBERG et al. 1992). In the Hubelj spring 90 % of analyzed samples were in this range while in the Vipava spring 87 %. The highest value of coefficient for the rest of samples was in the Vipava 1.24 and the lowest 0.85. In the Hubelj the highest coefficient was 1.19 and the lowest 0.85. The calculated ion difference (GREENBERG et al. 1992) was for the Hubelj between -3,5 % and -1-1.6 % and for the Vipava between -3.4 and -1-1.6 %. The summary of the measured concentrations of single parameters is presented in Tab. 4.1. In both springs the most changeable parameters have been conductivity and bicarbonate. The differences between minimum and maximum values have been higher in Vipava than in Hubelj. The changes of calcium concentration have been higher in the Vipava while the changes of magnesium concentration higher in the Hubelj (Fig. 4.6). For the establishment of seasonal changes in the investigation period of time we used AARDVARK (WRc 1995) seasonal model. In the Hubelj spring Tab. 4.1: The summary of the weekly samples in the springs Vipava and Hubelj in the entire investigation period TUE SPRING HUBELJ Parameter Number of samples Minimum value Maximum value Mean value Median value Standard deviation Conductivity - pS/cm - 25° C 145 155 273 217 219 14.4 pH 140 7.2 8.5 8.0 8.1 0.23 Calcium 145 26.1 45.8 38.2 38.3 3.4 Magnesium 144 3.7 11.1 6.9 6.7 1.5 Sodium 145 0.4 1.3 1.0 1.0 0.16 Potassium 145 0.1 0.5 0.2 0.2 0.04 Bicarbonate 114 106.8 158.6 141.7 143.4 6.1 Nitrate 143 3.8 10.4 5.9 5.6 1.1 Sulpliate 144 5.3 17.4 9.0 8.7 1.9 Chloride 144 1.2 7.7 2.0 1.8 0.75 THE SPRING VIPAVA 4/2 Parameter Number of samples Minimum value Maximum value Mean value Median value Standard deviation Conductivity - |jS/cm - 25° C 142 207 333 270 269 22.9 pH 140 7.3 8.4 8.0 8.1 0.19 Calcium 142 28.4 67.2 54.9 55.2 6.4 Magnesium 140 1.1 5.8 3.2 3.1 0.82 Sodium 141 0.5 3.3 1.5 1.5 0.46 Potassium 141 0.1 2.3 0.39 0.3 0.25 Bicarbojiate 103 128.1 213.5 17M 164.7 16.0 Nitrate 142 3.4 9.4 6.6 6.0 0.98 Sulphate 142 7.8 20.1 11.2 10.8 1.7 Chloride 142 1.5 3.9 2.3 2.2 0.44 we found seasonal changes for conductivity, Ca, Mg, Ca/Mg, bicarbonate and nitrate (Fig. 4.7). For other measured parameters the seasonal changes had not appeared. In the Hubelj spring the parameters characterizing the geological origin showed the seasonal changes. The conclusion from the seasonal model could be the hinterland of the Hubelj is not changing a lot in different hydrological conditions. In the Vipava spring only conductivity, the sum Ca + Mg and bicarbonate disclosed the seasonal changes. We could presume the hinterland of the Vipava 12 10 8 ♦ ♦ ♦ i ♦♦ ^ 1 a 6 - f u % \ 4 P 30 40 50 Ca (mg/1) 60 70 ♦ Hubelj o Vipava Fig. 4.6: Calcium and magnesium concentrations in the springs Hubelj and Vipava (412) from the analyses of all weekly samples taken during the observation period. is changing at different hydrological conditions. Namely the concentrations of Ca and Mg are changing very unregularly (Fig. 4.8). Very similar behavior we establish by the comparison of the ratio Ca/Mg with the flow (Fig. 4.9). In the Hubelj the ratio is very constant while in the Vipava much more variable. However, we observed the diminution of the magnesium concentration in the Hubelj up to the discharge about 5 mVs (Fig. 4.10) while in the Vipava spring this interdependence did not occur. Other analysed parameters (pH, sodium, potassium, sulphate, and chloride) have not shown any seasonal variation. Probably they are influenced besides geological structure from pollution sources (wastewater, fertilizers) as well. Finally we tried to find out which time period and frequency of sampling would be enough to get satisfied statistical confidence level. The calculation of the statistical characteristics showed that the results for one year weekly sampling gave us almost the same result than three years long weekly sampling (Tab. 4.2 and Fig. 4.11). For the comparison we choose the year 1994 which was after hydrological characteristics a dry year and the year 1995 which was after hydrological characteristics an average year. T-V Fig. 4.7: Seasonal variation of conductivity, Ca/Mg ratio, calcium, magnesium, bicarbonate and nitrate in the Hubelj spring during the whole investigation period (weekly samples). I r-T-i—S h k k k i TTS- Fig. 4.8: Seasonal variation of conductivity, the sum of calcium, magnesium and bicarbonate in the Vipava spring 412 during the whole investigation period (weekly samples). Fig. 4.9: Measured Ca/Mg-mtios versus discharge of the Hubelj and Vipava (412) springs for all weekly samples. 10 20 30 Flow 40 50 ♦ Hubelj o Vipava Fig. 4.10: Analysed Mg concentration versus discharge in the Hubelj and Vipava (412) spring for all weekly samples. Tab. 4.2: The summary of the weekly samples in the spring Vipava and Hubelj in year 1994 and 1995. IHE SPRING HUBELJ Parameter Number of samples Minimum value Maximum value Mean value Standard deviation Year 1994 1995 1994 1995 1994 1995 1994 1995 1994 1995 Conductivity - |jS/cm - 25 "C 51 49 155 170 273 237 218 216 19.2 13.4 pH 46 49 7.2 7.2 8.3 8.5 8.0 8.0 0.27 0.21 Calcium 51 49 34.3 30.9 44.2 42.5 39.5 37.8 2.2 2.7 Magnesium 51 48 3.9 3.7 11.1 10.5 7.2 7.1 1.6 1.6 Sodium 51 49 0.9 0.8 1.2 1.2 1.0 1.0 0.08 0.14 Potassium 51 49 0.2 0.1 0.5 0.3 0.2 0.2 0.04 0.04 Bicarbonate 51 39 106.8 122.0 158.6 158.6 142.7 140.6 11.4 10.1 Nitrate 51 47 4.6 4.8 8.7 10.1 5-9 5.8 0.97 0.88 Sulphate 51 49 5.3 5.8 15.5 17.4 9.1 9.1 2.1 2.1 Chloride 51 49 1.3 1.5 3.3 2.5 2.0 1.8 0.38 0.31 THE SPRING VIPAVA 4/2 Parameter Number of samples Minimum value Maximum value Mean value Standard deviation Year 1994 1995 1994 1995 1994 1995 1994 1995 1994 1995 Conductivity - pS/cm - 25° C 49 48 228 207 333 325 270 269 24.6 25.7 pH 47 48 7.5 7.4 8.3 8.4 8.0 8.0 0.18 0.17 Calcium 49 48 46.8 28.4 65.3 67.2 56.3 53.8 4.2 6.8 Magnesium 49 46 1.1 1.4 5.S 5.0 3.3 3.3 0.93 0.73 Sodium 49 47 1.1 0.8 2.3 3.3 1.6 1.5 0.25 0.40 Potassium 49 47 0.2 0.2 0.7 2.3 0.4 0.4 0.11 2.3 Bicarbonate 45 35 137.3 128.1 201.9 213.5 169.3 166.3 16.1 13.7 Nitrate 49 48 5.2 3.4 8.0 8.4 6.3 6.7 0.62 0.92 Sulphate 49 48 7.8 8.2 17.5 14.5 10.9 11.3 1.7 1.4 Chloride 49 48 1.5 1.6 3.9 2.9 2.3 2.2 0.46 0.34 12 ^ 10 - 8 - i B 6 ' M S 4 - 2 - 0 ^ 30 1994 ♦Vn ♦ ♦ 40 o o o CO o o 50 Ca (mg/l) I ♦ Hubey o Vipava 60 70 12 : 10 8 1 B 6 i M S i 4 - 2 J ♦ \ * ♦ ♦ ♦ O 30 40 1995 C 50 Ca (mg/l) ♦ Hubelj o Vipava o o o 60 70 Fig. 4.11: Calcium versus magnesium concentration in the Hubelj and Vipava (4/2) spring, separately for the weekly samples in the hydrological dry year 1994 (above) and the hydrological average year 1995 (below). 4.1.4. Comparative measurements of the Vipava springs (J. KOGOVŠEK) In the years 1964, 1965 and 1979 HABIČ (1983) already made the comparative measurements in the several Vipava springs (Fig. 4.12) when he compared the temperature and carbonate levels. Based on five series of measurements in March, May, June, November and December he stated that the southernmost springs Pod Lipo and Pri Kapelici are the most warm, 0.1 to 1.3° C warmer than other Vipava springs,- and that the variations in temperature of all the Vipava springs do not exceed 1,5" C during a year. Repeated measurements and analyses in the Vipava springs were done within the 7. SWT project. At the time of low and lowest waters we measured at all the seven springs of the Vipava their temperature, specific electric conductivity, pH and we analyzed total hardness and carbonate, calcium, Vlpsva4/7 Vipava 4/4 Vipava 413 Vipava 4/2 Vipava 4/1 chloride, nitrate and sulfate levels to find out the differences or similarities. The measurements and samplings took place on July 28 and December 2, 1994, May 25, 1995 and June 3 and September 16, 1996. The measured parameters of the spring Pod Farovžem Levo 4/7 differ considerably from the others where the differences are smaller. It reached the highest values of the specific electric conductivity (the average value was 361 (iS/cm), the highest total hardness (the average value was 3.82 meq/1), and «1 «2 «3 «4 «5 «6 «7 Vipava aoutcss -samm -«-se-iZM -«-asisse -O-OOML» -*-femm Fig. 4.13: Temperature variations in the Vipava springs at low and lowest water level. 4rt 4a 4» «4 «5 «8 «7 -ZKiBtSS -o-tBSKss -»-lenMel Fig. 4.14: Variations in the specific electric conductivity in the Vipava springs at low and lowest water level. also the highest levels of carbonate and calcium as well nitrate and sulfate. At other springs only smaller differences were perceived. Compared with the spring 4/7 they have an average a 55 p,S/cm lower SEC, and 0.6 meq/1 lower carbonate and calcium levels and total hardness. Regarding the temperature (Fig. 4.13) the spring 4/7 is very constant during a year. During mentioned measurements we recorded the temperature as always between 10.2 to 10.5° C. The temperature of other springs varies over the year by up to 1.5° C. In the observation time the temperatures of all the springs, with exception of 4/7, varied by from 0.2 to 0.3° C. Only in spring time when snow melts in the catchment area of high Nanos Mt. (measurements in May and June) the springs Pri Kapelici 4/1 and Pod Lipo 4/2 had higher temperatures (0.5 to 1,0° C) than the average temperature of other springs. This confirms the Habic's supposition that these springs are locally more influenced by sunny slopes of Nanos. Also other measured parameters indicate smaller variations at the spring 4/7 than at the others. SEC varied by 32 )iS/cm, while at the others by 51 |j.S/cm (Fig. 4.14). Yet the differences between the springs, with exception of the spring 4/7, in the observed time are very small, up to 9 )J,S/cm; the exceptional ones are the measurements of May and June when the range of difference is 15 |J.S/cm. The carbonate and calcium level varied at the spring 4/7 by 0.2 meq/1 while at the other springs it was more than 0.4 meq/1. The total hardness oscillated at the spring 4/7 in an interval of 0.4 meq/1 while at others springs*it was 0.6 meq/1 (Fig 4.15). There are considerably lower values of SEC, and also of carbonate and calcium levels in spring time, and higher values at the end of summer and in autumn indicating seasonal variations. m *a m At* AI5 AB Vipava sources Fig. 4.15: Variations in the total hardness in the Vipava springs during low and lowest water level. 4.2. OBSERVATION OF SINGLE EVENTS 4.2.1. Daily sampling in the springs Hubelj, Vipava and Mrzlek (M. ZUPAN) Tab. 4.3: The summary of the daily sampling in the springs Vipava and Hubelj in the investigation period from 18-09-95 to 29-02-96. THE SPRING HUBELJ Parameter Number of samples Minimum value Maximum value Mean value Standard deviation Conductivity - |jS/cm - 25° C 134 118 237 216 12.3 pH 134 7.8 8.5 8.2 0.16 Calcium 134 29.8 43.3 37.9 2.5 Magnesium 134 4.0 9.3 6.9 1.2 Sodium 134 0.2 2.1 0.9 0.25 Potassium 134 0.1 0.3 0.2 0.04 Nitrate 134 4.5 8.6 5.6 0.51 Sulphate 134 5.8 16.4 9.3 1.8 CWoride 134 1.2 2.5 1.9 0.23 THE SPRING VIPAVA 4/2 Parameter Number of samples Minimum value Maximum value Mean value Standard deviation Conductivity - pS/cm - 25° C 169 233 386 274 195 pH 169 7.7 8.5 8.1 0.16 Calcium 169 30.3 67.2 55.8 4.8 Magnesium 169 1.7 6.6 3.5 0.92 Sodium 169 0.9 2.4 1.4 0.28 Potassium 169 0.2 3.3 0.5 0.62 Nitrate 169 2.8 9.1 6.5 1.1 Sulphate 156 7.2 16.9 11.0 1.9 Chloride 169 1.5 3.1 2.1 0.30 In the time period from September 1995 to February 1996 daily samples in the springs Hubelj, Vipava and Mrzlek have been taken. From September 1996 to February 1997 we had taken the daily samples in the spring Vipava 4/2 (Fig. 4.12). The purpose of this sampling was to follow the changes in shorter time period and to define the changes of physical and chemical parameters depending on the water quantity more detailed. At the same time we wanted to compare the results of long-term weekly observations during three years with the results of daily sampling in much shorter period of time. The results of these observations are shown in the Tab. 4.3 and Fig. 4.16, 4.17 and 4.18. The distribution of the results of daily sampling in six-month period is very similar to those of weekly sampling. It means that we could get the information in much shorter time if we would sample with higher sampling frequency. The calculation of one-month daily samples did not give enough rehable information. In the first period of sampling for the 3rd tracing experiment (Chapter 6) we took the daily samples for physical chemical analyses in the spring Mrzlek both on the right bank of the Soča and in the pump station for water supply. The daily samples we took from August 9, 1995 to August 17, 1995 and from August 30, 1995 to September 23,1995. Afterwards we continued with weekly sampling till December 12, 1995. The data should give us some information Fig. 4.16: Calcium and magnesium concentrations in the Hubelj and Vipava (4/2) spring; analyses from all daily samples during the investigation period. eg U 35 30 -25 -20 15 10 5 ^ O ^o 0 0 o o o o 10 20 30 Flow 40 50 Hubelj Ca/Mg o Vipava Ca/Mg 60 Fig. 4.17: Measured Ca/Mg ratios versus discharge in the Hubelj and Vipava (412) spring; analyses from all daily samples during the investigation period. Fig. 4.18: Analysed Mg concentrations versus discharge in the Hubelj and Vipava (412) spring; analyses jrom all daily samples during the investigation period. about the influence of the Soča to the Mrzlek spring on both samphng sites. During the dry period in the beginning of August the magnesium coneentra-tion in the pump station was higher than in the spring while the calcium concentration was lower in the pump station. This fact would allow us to presume that some influence of the Soča river to the spring exist (Fig. 4.19). Namely the magnesium concentration is significant higher in the Soča while the calcium concentration is lower. Mean concentration of magnesium in the 60 - - 290 1 280 •t A »270 ■ Ž i ^ 260 ■> 'S + 250 o O 30 »44444miH^tm^ i 2 a 2 2 Š Š 2 ž ^ H S 5 r» 2 5' 5 5 y s Š J Š Š E 2 J § s is Spring Ca Pump station Ca o— Conductivity (Spring) BO 7------ -------------------------------------^ 290 I 5* * * i I 00 ■ B^f** - 270 M 1 4 M Q , - 250 -a Č - ^ - o ^ - ^ ^ o , ,, q ; 240 »23232 5 2 5 2 § gTTITITTSlllsss S S Š 2 2 § S U Spring Mg Pump station Mg -e- Conductivity (Spring) Fig. 4.19: Conductivity and calcium concentration (above) and conductivity and magnesium concentrations (below) in the Mrzlek spring and in the pump station, analyses from all daily samples during the investigation period. Soča during the daily sampling period was 10.6 mg/1 while in the Mrzlek it was 3.9 mg/l. Mean calcium concentration in the same period of time was in the Soča 43.3 mg/l and in the Mrzlek 48.4 mg/1. In September during rainy period the magnesium concentration was very similar in both sampling points while the calcium concentration was much different. The seasonal model showed the catchment area of the Hubelj is not changing much at different hydrological conditions. The catchment area of the Vipava seems to bo more changeable at different hydrological conditions. The hydrochemical analyses of weekly samples in the period of three years and the analyses of daily samples taken during six-month period gave ver\' similar characteristics. The results of the weekly sampling during one year period would be satisfactory as well. 4.2.2. Water pulse of the Vipava spring - Pod Lipo 4/2 (J. KOGOVŠEK) After a medium-sized water pulse in the second half of September the Vipava discharge was decreasing through the whole of Octobcr. On November 11, 1995 the discharge increased (the occurrence of the first water pulse) and reached its maximum of 9.6 cubic meters two days later. During the following two days it decreased to a half. On the next day, November 16, the discharge increased again and reached its maximal value of 51.9 cubic meters on November 17, 1995 at 3 p.m., thus forming the second water pulse (see Fig. 4.20). In this time wc manually sampled Vipava at the spring Pod Lipo, No. 4/ 2 for physico-chemical analyses. We measured the temperatvire, specific clectric conductivity and pH and we determined carbonatc, calcium and total hardness, and chloride, sulfate, nitrate and phosphate levels. During the first, smaller, water pulse a slight increase of carbonates, calcium and SEC was recorded, probably due to replacement of old weiter from a recharge area, for there was no considerable change in discharge in the last 45 days. The second water pulse was followed by a rapid increase reaching the maximal value of discharge in 27 hours. The first sample was taken 7 hours after the minimal discharge at the beginning of water pulse when the discharge reached twice the minimum. The carbonate and calcium levels were lower by 0.3 meq/1 than at the first lower water pulse. Unfortunately we did not sample in the intermediate time between the two water pulses. The discharge increase in the second wave was followed by a slight increase of carbonates and calcium, but when the maximal discharge rapidly decreased they decreased also. Later, when the discharge decrease was slower the hardnesses were in slight increase (Fig. 4.20). Minor deviation was recorded in calcium level, as at the initial decrease its concentration decreased slightly less and during continuing slower discharge decrease remained higher compared to Fig. 4.20: The water pulse (Q) and the Ca/Mg ratio the Vipava spring in November 1995. carbonates and total hardness during the beginning of the water pulse, although the increase of all three hardnesses was proportionate. Specific electric conductivity (SEC) is proportionate to total hardness. Dependence of SEC on discharge is seen in Fig. 4.21. Well seen is the difference of SEC dependence on discharge during its increase and decrease. During the first smaller water pulse also SEC increased together with carbonates and calcium. During the second water pulse the SEC firstly slowly decreased when the discharge was in increase, and when it reached the value of 50 cubic meters SEC rapidly decreased until maximal discharge was attained and at that time the minimal value of SEC was recorded. During the discharge decrease SEC at first increased slowly, but when the discharge reached the value of about 10 cubic meters, SEC started to increase faster). The changes in SEC are relatively small, being the difference between the minimal and maximal value within a water pulse 20 to 25 )xS/cm, similar to that recorded at carbonates and calcium. In any case all these measurements and statements must be checked and confirmed by observation of greater number of water pulses and by isotopic analyses and other approaches. 4.10 3.90 3.70 3.50 3.30 3.10 2.90 2.70 Cartxxi.h. Cah. -Total h. « H 07.11. 09.11. 11.11. 13.11. 15.11. 1995 17.11. 19.11. 21,11. 23.11. time Fig. 4.21: Variations of the carbonate and the calcium levels as well as of the total hardness in the Vipava spring during the water pulse in November 1995. Fig. 4.22: Dependence of the conductivity (SEC) from the discharge during the Vipava water pulse in November 1995. Level contents during the Vipava water pulse in November 1995. 14 12 10 8 § 6 O - Chlorides - Sulphates - Nitrates □ □ D—D 0------ O O ° „V .........° <3n>-$äoo-^---------o 95-11-11 95-11-13 95-11-15 95-11-17 95-11-19 95-11-21 95-11-23 Fig. 4.23: Variations in the chloride, nitrate and sulfate contents during the Vipava water pulse in November 1995. Determination of phosphate and chloride levels did not display any changes during the two water pulses, or, maybe they were so small that we did not register them. The phosphate concentration was at the limit of detection (0.01 mg PO/7!), and the chloride concentration 2 mg Cl/l (Fig. 4.22). In the first water pulse we recorded a slight increase in nitrate levels of 1 mg NO,"/l. During the second water pulse the values only oscillated slightly. During both water pulses a small, but permanent increase in nitrate level was recorded. The initial value of sulfate level, 9.5 mg SO^^/1 at the beginning of the first water pulse increased to 12.5 mg SO^-'/l during the maximal discharge and later it decreased. Similar increase was recorded at the beginning of the second water pulse (Fig. 4.23). When a discharge approached the starting value also the level of sulfate reached the starting value before both water pulses. 4.2.3. The Use of Silica to characterise the allogenic Flysch Component in Vipava Springs during the observation of Single Events (V. ARMBRUSTER, C. LEIBUNDGUT) 4.2.3.1. Introduction The Vipava springs show some characteristics of a karst spring, that is influenced by an allogenic flow component. Its catchment borders on Eocene flysch in the East, where sinking streams drain parts of the flysch area and probably have a connection towards Vipava springs. The soils and the bedrock of the flysch area around Postojna release considerably more silica than those of the karst plateaux of Nanos and Hrušica. As a consequence, silica could be used as a natural tracer to make hydrograph separations of Vipava springs' water into karst water and allogenic flysch water during a runoff event. The dynamics of the allogenic flysch component could be characterized and a rough estimation of the Vipava catchment area, which is made up by flysch, could be given. 4.2.3.2. Methods The kinetics of silica release are fast and thus, silica contents hardly depend on residence times, but almost exclusively on different flowpaths of water. Nevertheless, time dependent silica contents have been determined for the flysch as well as for the karst component. To obtain a representative sihca content of the flysch component, the water of Lokva river on the flysch area has been sampled at Predjama Castle, where it sinks underground at the karst flysch border and has a proofed connection to Vipava springs. To obtain a representative sihca content of the karst component, Hubelj karst springs has been sampled, which is uninfluenced by flysch areas. The samples of the two components and the samples of Vipava springs during a heavy precipitation event in April 1996 were analyzed photometrically for dissolved sihca. A two component mixing model has been used for the hydrograph separations. 4.2.3.3. Results During the sampled period from March the 27"" until April the 12"" 1996, the karst plateaus were partly snow-covercd, and the discharge of Hubelj and Vipava springs was relatively high, as snowmelt was taking place. During a heavy precipitation event on April the 1" and 2"'' about 90 mm of rain were falling on the Vipava catchment (Fig. 4.24: (A)) and caused strong rises in the discharge of the karst springs. During the precipitation event the rain turned into snow and covered the karst plateaus completely. On the lower neighboring flysch area near Postojna, no snow was deposited and the rainfall amounted to 110 mm, causing extreme floods in the flysch streams. After the precipitation event the discharge of Hubelj and Vipava springs decreased until April the 5"\ Then warm and sunny weather caused a strong snowmelt runoff event with daily discharge fluctuations in the karst springs (Fig. 4.24: (C)-(D)). Flysch Water Fig. 4.24 (B) shows the assumed discharge of water from the flysch area, drained by sinking streams, and its sihca content during the observed period. On the basis of the peak discharge of the two biggest sinking streams Lokva and Belščica and the water level record of the Belščica the discharge was E £ ■S % a % a 0 20 40 7,5 5.0 2.5 0.0 40 30 20 10 0 UU (JO- - - ~ (A) Precipitation (B) Flysch Area O.^D......... - 3.5 - 3.0 ^ L 2.0 ; (C) Hubelj Springs 0-- -CID' §i>........ > \ A 93-01 93-07 94-01 94-07 95-01 95-07 96-01 Fig. 5.9: Seasonal variation of S"^0-contents of water from the karst springs Kajža, Hotešk, and Podroteja. -7,0 w O CO 'ČO —O—Hubelj - - A- - ■ Mrzlek - - Vipava -9,5 -- -10,0 H-1- H-(- ^-1-j- 93-01 93-07 94-01 94-07 95-01 95-07 96-01 Fig. 5.10: Seasonal variation of S'^O-contents of water from the karst springs Hubelj, Mrzlek, and Vipava. Acta carsologica, XXVIjl (1997) - (Karst hydrogeological investigations...) Tab. 5.3: Estimated mean altitude of the catchment area of the six springs. Name of the spring [%o] Altitude [m a.s.l.] Kajža -7.52 ± 0.20 620 ± 80 Hotešk -8.18 ± 0.24 900 ± 100 Mrzlek -8.24 ± 0.29 920 ± 120 Hubelj -8.43 ± 0.23 1000 ± 100 Vipava -8.46 ± 0.33 1010 ± 140 Podroteja -8.57 ± 0.24 1060 ± 100 Soča River The S'^^O-values of the water from the Soča river shows the analogue seasonal variation as observed in the water of the springs (Fig. 5.11), From the average S'^'O-value (-8.46 ± 0.30 %o ), the mean altitude of the catchment area was estimated to 1010 ± 130 m a.s.L. The general trend over the whole observation period, which was mentioned for the 5'®0 content of precipitation samples, is also obvious in the 5^^0-values of the river water with a delay of the winter precipitation possibly caused by a temporal storage of the snow cover. -7,0 -7,5 -8,0 £ 0 -8,5 00 'tO -9,0 -9,5 -10,0 ■ Soča river 93-01 93-07 94-01 94-07 95-01 95-07 96-01 5.1.4.2. Mean residence time In the literature, several mathematical models known as so-called Black-Box-Models are used to estimate the mean transit times from long term isotopic observations (MALOSZEWSKI & ZUBER 1982, 1996). Considering the hydrological situation in the area under investigation, the dispersion model (DM) seems to be applicable for the interpretation of the isotope data obtained during base flow conditions. Since the groundwater system is under steady state conditions, the relation between input and output concentration of the nonradioactive tracer is given by the following convolution integral: t C„^t) = \c.,„„{x)g{t-x)dx (3) 0 where and are the input and output concentrations as functions of time, t, respectively, d,n&g(t) is the weighting function defining the transit time distribution in the system. Theg(t) function for the dispersion model is defined as follows (MALOSZEWSKI & ZUBER 1982): 1 if {l-tlTf' g{t)= , -exp ---^ (4) The main parameter of this model is the mean transit time of water (T), which is defined as r = ^ (5, Q ^ where Q is the mean volumetric flow rate through the system and V is the volume of water in the system. P^ is the dispersion parameter, which describes the variance of the transit time distribution. With stable isotopes, a simpler procedure can be apphed, if the isotopic input curve can be approximated as a sinusoidal function with the period of one year (see chapter 5.1.2.1): C,„„(0 = A„sin((00 (6) where w = 2p / (year), and A^ is the mean amplitude of the input function. Introducing Eq. (6) in Eq. (3) yields: = sin(cor + (p) (7) where B is the mean amplitude of the output function, and cp is the phase shift, which in the case of the dispersion model is equal to: (p = r (8) The mean transit time can be calculated from the amplitude ratio f = B / A as: n ' n 1 T = coV In/ (9) The values of parameters cp and f are determined directly from experimental data. By using the Eqs. (8) and (9) iteratively, the mean transit time of water (T) and the dispersion parameter (P^) can be calculated. The amplitude A^ (input function) was estimated from the variation in precipitation at representative stations shown in Figure 5.2. The S'^'O output function of the selected karst springs are plotted in Figures 5.9 and 5.10. These data are the basis for the estimation of the amplitude B^ of the karst springs under investigation. Tab. 5.4: Mean transit time (T) and dispersion parameter (P^ calculated for selected springs. Name of the spring T [months] Po [ - ] Kajža 5.4 0.28 Hotešk 5.5 0.30 Podroteja 5.5 0.29 Hubelj 5.8 0.25 Mrzlek 5.0 0.25 Vipava 4.4 0.30 The evaluation of the ■''H data gives similar results. The -^H values of monthly samples from the Vipava spring correspond with the actual 'H content of precipitation, thus may indicate a relatively short mean residence time of the spring water in the underground (Fig. 5.12). There is no significant increase/decrease of the ^H content even during low water periods. Only the seasonal variations of the -^H content in precipitation (see also Fig. 5.12) are reflected in the ^H graph of the Vipava spring. A mean transit time of about 0.4 years may be estimated from the comparison of the ^H amplitudes of precipitation and spring water. This corresponds with the results above concluded from the 5'®0-values. However the mean transit times of around 5 months (see Tab. 5.4) seem to be too low considering the hydrogeological situations. Therefore a mixture of two water components, having mean transit times of weeks (karstic channels) and mean transit times of years (outflow from the karst massif) could not be excluded. While, to separate these two components a longer observation period is necessary. 25 20 „15 t X " 10 5-- 0 tr j- ■ H-3 Vipava ---discharge Vipava -H-3 precipitation Podl^raj ** " H-3 precipitation mean "Tn I \ ' 1 / i/\/ v I I I I I I I M I I I I I I I I I I I t I I I I I I I I I I I I 93-01 94-01 95-01 96-01 25 20 15 E, (D «I 10 ^ u M Fig. 5.12: Discharge and content of monthly samples from Vipava spring together with the monthly and weighted mean ^H-values of precipitation at the meteorological station Podkraj. 5.1.5. Short term observation In addition to a quantitative approach to the course of hydrological events, isotopic investigations also provide insight into the age structure of waters. Such knowledge helps in drawing conclusions on storage processes in hydrological systems and on the composition of the runoff; that is on the relative shares of base flow, direct runoff following storm events, and interflow. Distinguishing the components of runoff is an important basis for hydrological assessment of potable water reserves in a particular region. To apply this method, an adequate amount of precipitation is necessary as well as a distinct difference in the isotope content of the water components mentioned above. Considering the seasonal variations in the content in precipitation, major deviations in the content from single precipitation events from the mean value of the system can be expected in winter and in summer. In the area under investigation, precipitation in winter generally takes the form of snow, and does not directly reach runoff. Therefore, mid-summer would be the most favourable period for such research. As mentioned above, isotope data can be used to estimate the portion of water flowing directly through the karstic channels. To do this, the isotope content has to be monitored in the karstic springs before and during a discharge event and in the precipitation producing this event. The travel time through the karstic system of the fast-flow portion of a precipitation event can be estimated from the time delay between the respective peaks in precipitation and discharge, assuming a piston flow model. The percentage of direct flow water (d) is obtained by calculating the simple mixing equation using the 5'^0-values of precipitation and discharge as follows: CojTZ^ (10) d = ^BF ^PE ~ ^BF with: Cpg = weighted mean content in discharge event Cpg = weighted mean content in precipitation event Cgp = mean 5'®0 content in discharge before the event at base flow conditions 5.1.5.1. Vipava spring For the Vipava spring, the determination of the direct water component was only possible from the isotopic data obtained during the event on 17 November 1995. The discharge measurements of the Vipava spring from October 1995 until March 1996 are plotted in Figure 5.13 together with the precipitation amount of the meteorological station Podkraj. The precipitation and discharge are in phase, only with the low values a shift of some days can be recognised. Isotope data from the single precipitation events are shown in Figure 5.14. Unfortu- 60 50 ■40 (D ra30 (D I 20 X) 10 i i 1 -discharge Vipava -precipitation amount Podl (O I -9,0 95-08-01 95-08-16 95-08-31 95-09-16 95-10-01 95-10-17 95-11-01 Fig. 5.21: Daily variation of S"^0-content of water and discharge from the Hubelj spring. separation. The reaction in the content of the discharge in the Hubelj spring is given in Figure 5.21 and the resuhs are summarised in Table 5.5. 5.1.5.3. Additional karst springs Besides these two main spring systems Vipava and Hubelj, five additional karst springs were sampled on a daily basis during the spring of 1994. P to -6,5 -7,0 -7,5 -8,0 -8,5 -9.0 -9,5 94-04-01 - Lijak ■Kajža ■Hotešk - Podroteja • Divje Jezero r-l-. rfn 94-04-16 94-05-01 94-05-16 94-05-31 Fig. 5.22: Daily variation of S'^O-contents of water from the karst springs Lijak, Kajža, Hotešk, Podroteja, and Divje Jezero. O to 1o 0,0 -2,0 -4,0 -6,0 -8,0 -10,0 -12,0 -0-18 0tlica • precipitation amount Otiica : I flIU r+A. -I- 120 100 80 "E E, 60 c o 40 i 20 A 94-04-01 94-04-16 94-05-01 94-05-16 94-05-31 Fig. 5.23: Daily precipitation amount and S"0-content of precipitation from the meteorological station Otiica. The temporal variations of the S'^^O-values are shown in Figure 5.22. It was only possible to calculate the direct runoff portion with the data obtained from the Lijak spring water during the 19 May 1994 event (see Tab. 5.5). The precipitation amount and the discharge values are documented together with the corresponding isotope data in Figure 5.23 and 5.24. For the springs Podroteja and Divje Jezero, the content of precipitation and discharge were too close together and Eq. (10) could not be apphed. The karst springs Kajža and Hotešk were not sampled during the mentioned precipitation event. O CO -6,0 -6,5 -7,0 -7,5 -0-18 Lijak - discharge Lijak -8,0------------------ -8,5 -9,0 94-04-01 1 12 10 d) CO 94-04-16 94-05-01 94-05-16 94-05-31 Fig. 5.24: Daily variation of 6'^O-content of water and discharge from the Lijak spring. 5.1.5.4. Results The results obtained by calculating the portion of direct water component during single events of selected springs using contents are summarised in Table 5.5. The travel time between precipitation event and discharge response are on the order of one to two days (see Fig. 5.13 and 5.19). Tab. 5.5: Portion of direct water component during single events of selected springs calculated using "^O contents. Name of the spring Date of event C^p [%o] CpE [%o] d [%] Lijak 1994-05-19 -6.85 -8.63 -8.15 73 Vipava 1995-11-15 -8.20 -4.90 -7.50 21 Hubelj 1995-08-28 -8.78 -6.67 -8.42 17 Hubelj 1995-09-20 -8.36 -7.40 -8.22 15 The portions of direct runoff in Hubelj and Vipava spring range between 15 % and 20 %, with slightly higher values indicated for the Vipava spring. In contrast, the water of the Lijak spring shows a pronounced portion of precipitation water. The 5"^0-values of the karst springs shown in Figure 5.22 could also be used to calculate the mean altitude of the catchment areas of these individual springs. This is due to the fact that the discharge was very low during the observation period, as shown by the discharge measurements of the Podroteja spring (Fig. 5.25). The average S'^^O-content was calculated for the period of 15 April to 15 May 1994. The uncertainty of the calculated altitude of the catchment areas results once more from the la criterion of the 5'**0-values. Tab. 5.6: Estimated mean altitude of the catchment area of the five springs Name of the spring [%o] Altitude [m a.s.l.] Lijak -6.92 ± 0.08 370 ± 30 Kajža -7.69 ± 0.07 690 ± 30 Hotešk -8.27 ± 0.06 930 ± 25 Podroteja -8.72 ± 0.05 1120 ± 20 Divje Jezero -8.89 ± 0.05 1190 ± 20 60 40 -- - discharge Podroteja A 0 94-04-01 94-04-16 94-05-01 94-05-16 94-05-31 Fig. 5.25: Daily variation of discharge from the Podroteja spring. The estimated mean altitudes of the catchment areas of the given springs are in agreement with the altitudes calculated by the 5^®0-values of the yearly variation (see chapter 5.1.4). 5.2. DISSOLVED INORGANIC CARBON ISOTOPE COMPOSITION OF WATERS (J. URBANC, B. TRČEK, J. PEZD1Č, S. LOJEN) The objective of this research is to determine whether the isotope composition of TDIC in water and the chemical composition of water in the outflow from a karst aquifer can be used to interpret the carbon isotope composition and partial pressure of soil CO^ in the aquifer's recharge area. Further, an attempt was made to establish which model of carbonate rock dissolution in water can be applied to interpret initial conditions and define the degree of accuracy with which the initial conditions can be described if the only data available are those of the isotopic and chemical composition of water in the outflow from a carbonate aquifer. Thus, in our research, the carbon isotope composition and partial pressure of soil COj measured in the recharge area of a karst aquifer were compared to the values, calculated from the isotopic and chemical composition of water in the outflow from aquifer. Previous observations have shown that the formation of soil CO^ is to the greatest extent conditioned by soil temperature (BILLES et al. 1971; DORR & MUNNICH 1980; KIEFER & BROOK 1986; WOOD et al. 1993), by the quantity of organic matter in the soil (WOOD et al. 1993) and by soil moisture (KIEFER & BROOK 1986). Most of soil CO^ passes into the atmosphere, only a minor part of the total CO, is washed into the ground by precipitation (WOOD & PETRAITIS 1984; QUADE et al. 1989; HENDRY et al. 1993). Soil CO, can originate from the decomposition of organic matter or root respiration (WOOD & PETRAITIS 1984; HENDRY et al. 1993; DUDZIAK 1994). Some investigations indicate that during carbonate dissolution in soil, the solution equilibrates with soil CO^. Thus this is an open system of carbonate dissolution (REARDON et al. 1979; QUADE et al. 1989^ while indications for the closed system of carbonate dissolution in the soil were also present (DEINES et al. 1974). 5.2.1. Carbon Isotope Composition In Individual Parts Of The Researched System The carbon isotope composition of water in the outflow from aquifer can be influenced by the carbon isotope compositions of soil CO^, carbon isotope composition of the carbonate rock, and by potential changes of carbon isotope composition of water resulting from isotope exchange between the carbon from atmospheric CO^ and the carbon degassing from water CO^. 5.2.1.1. Characteristics of carbon isotope composition of soil CO^ Several sampling points underlying different vegetation covers and at different altitudes were chosen for the measurement of isotope composition and partial pressure of soil CO^. Three probes for the sampling of soil CO^ were placed in a forest with prevaihng beeches: in the Belca valley (sampling point with the lowest altitude), near Podkraj, and data obtained at Obli Vrh at an altitude of about 1000 m were also included in the investigation. The probes at Col and Grgar were located in soil underlying grass. The probe for the sampling of soil CO^ in a spruce forest was located near Podkraj. Samples of soil CO^ were taken using metal capillaries with an inside diameter of 1 mm, which were dug about 50 cm deep into the ground. Samples of soil atmosphere were transferred into preevacuated 0.7 1 glass ampoules. In the laboratory, atmospheric CO^ was isolated according to the usual procedure (CRAIG 1953) and its isotope composition was measured on the Varian Mat 250 mass spectrometer. From the quantity of isolated CO^ and the volume of the ampoule the concentration of CO, in the gas sampled was calculated. Dissolved inorganic carbon from water was extracted by adding concentrated HjPO^ acid to the water in vacuum (MOOK 1970). 2 1,8 --1,6 — 1,4 — ^1,2 --S 1 + o 0,6 --0,4 0,2 8 10 12 14 Soil temperature (°C) 16 18 20 □ Temp.-12 cm Temp. - 50 cm Fig. 5.26: Relation between soil temperature and partial pressure of soil CO^ in beech forest. 1,8--1,6--1,4 ---1,2 -- s ^ + Ü '^0,8 + 0,6 --0,4 --0,2 -- a □ 10 12 14 16 18 Soil temperature (°C) 20 22 24 □ Grgar-12cm o Col-12 cm • Col - 50 cm Fig. 5.27: Relation between soil temperature and partial pressure of soil CO^ in soil under grass. A linear correspondence between temperature and partial pressure of soil COj can be clearly observed (Fig. 5.26, 5.27). Compared to the soil underlying beech forest, the soil overlaid with grass has lower partial pressures of soil CO^. The smaller generation of CO^ is of course conditioned by a smaller transition of organic matter into the soil overlain with grass. Fig. 5.28 shows average partial pressures measured at individual locations, compared to the average soil temperature. Values measured at sampling points located under the same type of vegetation lie along the same line, and the inclination of P^o,"^ correlation lines for beech and grass is also similar. Beech forest is the prevailing vegetation in the research area, therefore the majority of carbon isotope composition values and partial pressures of CO, were measured in soil underlying beech forest. Monthly measurements of soil CO2 carbon isotope composition showed that most of the values lie between -17 and -23 %o (Fig. 5.29), while partial pressures of CO^ range between 0.07 to 1.2 % of the total atmospheric pressure. A certain interdependence between the carbon isotope composition and partial pressure of soil CO^ is evident from Fig. 5.28. Such correlation could result from the mixing of biogenic carbon, originating from the decomposition of organic matter in the soil, with the carbon from atmospheric CO,. In this case, the ratio between biogenic carbon and atmospheric carbon can be expressed by the mixing equation: . P, 5'-'C . F b b a a § »C. = --(11) P. P ... partial pressure a ... atmospheric b ... biogenic t ... total In the mixing model, the following 5"C concentrations were adopted: -23 %o for organic carbon, -8 %o for atmospheric carbon (KEELING et al. 1979), and 0.03 % for the partial pressure of atmospheric CO^. The curve of the mixing model is given in Fig. 5.29, indicating that modelled results are in good correlation with the values measured. Equation 11 was statistically proved, the test statistic F = 3.7-t-lO-' (TRČEK 1996). Thus it can be concluded that fluctuations in carbon isotope composition of soil CO^ can be to a great extent attributed to the mixing of biogenic and atmospheric carbon. In the above case, sampling points were located under the same type of plant, namely under beech. A different carbon isotope composition of biogenic carbon is to be expected in soil zones underlying other types of vegetation. Figure 5.30 shows the relation between the carbon isotope composition and 1.8 - 1,6 t I 1,4 -.1,2 - S o 0,6 — 0,4 - 0,2 -- Belca-beech (460 m) / iPodkraj-beech (860 mV-^ , ' ^ MGrgar-grass (390 m) ■ Podkraj-spruce (850 m) ,^ Col-grass (620 m) ■ Obli vrh-beech (1000 mY 8 10 12 14 Soil temperature - 50 cm (°C) 16 18 20 Fig. 5.28: Mean soil temperatures of different locations related to the mean partial pressure of CO^. -23 -25 H-^-1-f-1-^-^-1-h 0 0,2 0,4 0,6 0,8 -H-^-h- 1,4 1,6 1 1,2 pC02 (%) Belca-b o Podkraj-b x Obli vrh-b 1,8 Fig. 5.29: Relation between partial pressure of soil CO^ and its carbon isotope composition for soil in beech forest. partial pressure of soil CO^ for all types of vegetation covers sampled. It can be seen that samples from spruce forest show no significant deviation from the properties of CO^ in beech forest, while more considerable differences are observed in soils under grass covers. The samples taken from soil underlying grass near Col have a more negative isotope composition of biogene soil CO, of about -24 %c, while the samples from Grgar show a distinctly more positive isotope composition of the biogene component, about -21.5 %o. This difference in the carbon isotope composition of soil CO^ under the same type of vegetation is attributed to the different altitude and the different mean soil temperatures. The sampling point near Grgar is situated at an altitude of 390 m in rather Mediterranean climatic conditions, and that near Col is at 620 m above the sea level, where chmatic conditions are much harsher. The prevailing types of grass in warmer areas are those with the Hatch-Slack (C4) cycle which generates more positive 5"C values in plant tissues. On the other hand, the Calvin cycle (C3) prevails in grass from colder areas, giving more negative 5"C values of plant tissues (GERLING 1984). Thus it can be concluded that in the area of the Trnovsko-Banjška Planota, CO^ with varying isotopic properties enters the ground: the most negative values of biogenic carbon isotope composition are to be expected in CO^ from soil underlying grass and from higher-lying and colder areas (about -24 %o), soils underlying beech or spruce forests tend to have somewhat more enriched 5"C values of biogenic carbon (about -23 %o), and grass from warmer and lower areas give the most positive initial isotopic signal (about -21.5 %o). -22 -23 -24 0,8 1 1,2 1,4 1,6 1,8 pC02 (%) □ Grgar-g v Col-g Beica-b Podkraj-b Obli vrh-b x Podkraj-s 5.2.1.2 Carbon isotope composition of carbonate rocks The research area is for the most part composed of Mesozoic limestones and dolomites and flysch rocks. In all, 24 rock samples were taken for isotopic analyses. Measurements of carbon isotope composition of observed samples showed a range in 5"C values between 0 and +4 %o (Fig. 5.31). It can be observed on the graph that dolomites have mostly more enriched and 5'®0 values compared to limestones or flysch. o CO □ o 1 D -2 O 180-karb. limestone dolomite flysch Fig. 5.31: Carbon and oxygen isotope composition of the rocks on investigated area. 5.2.1.3. Isotope composition of the total dissolved inorganic carbon in the outflow The yearly curve of 5"C values in the outflow shows certain seasonal variability (Fig. 5.32 to 5.39). General characteristics are most clearly evident from the spring Hotešk (Fig. 5.32). The Figure shows that the most depleted S'-^'C values of DIG in the outflow are detected in late fall, usually in November. Then a rather rapid change towards more positive 5"C values takes HOTEŠK -16 Jan-93 Apr-93 Jul-93 Oct-93 Jan-94 Apr-94 Jul-94 Oct-94 Jan-95 Apr-95 Jul Date 13C-DIC © Alkalinity Fig. 5.32: Carbon isotope composition and alkalinity of Hotešk spring. place until spring, and a gradual depletion in values follows over the entire year to the late fall minimum. Such seasonal isotopic variability can be explained in the following way: Due to the correlation between pedotemperature and partial pressure of soil CO^, the gradual increase of soil temperature over the year results in an increased production of soil CO^. In the fall, soil temperatures are the highest, organic matter enters the ground due to lost leaves, which results in a maximum in soil CO^ partial pressure. A higher content of the biogenic component in soil CO^ is reflected also in the carbon isotope composition, which reaches its most depleted S'^'C values, and in the DIC isotope composition in the outflow, where the most depleted 5"C values were also detected. Lower soil temperatures in winter considerably hinder the processes of soil COj generation, consequently the soil atmosphere contains a higher percentage of atmospheric CO^ with more positive 5"C values. When the water from melted snow penetrates the soil in spring recharge area, a larger quantity of atmospheric carbon enters the system, resulting in enriched 6"C values in the outflow. A similar pattern of seasonal fluctuations can be perceived also in the other springs, except in the Hubelj, which shows a distinctly different 6"C isotopic curve (Fig. 5.33). HUBEU -13 -14 -15 -16 Jan-93 Apr-93 Jul-93 Oct-93 Jan-94 Apr-94 Jiil-94 Oct-94 Jan-95 Apr-96 Jul-95 Date -i^ 13C-DIC o Alkalinity rS -4,5 -4 -3,5 CT -3 P -2,5 .C -2 "S -1,5 < -1 -0,5 -0 Fig. 5.33: Carbon isotope composition and alkalinity of Hubelj spring. A comparison of carbon isotope composition variation amplitudes in the outflow is also very interesting. The springs Vipava (Fig. 5.34), Podroteja (Fig. 5.35), Hotešk (Fig. 5.32) and Prelesje (Fig. 5.38) show a fairly similar range of yearly 5"C values at about 2.5 %o . Yearly fluctuations of the carbon isotope signal are much larger in-the Hubelj, where the amplitude of 8"C values from spring 1993 to spring 1994 was over 6 %o (Fig. 5.33). This indicates that Hubelj has a higher aquifer water exchange rate, resulting in a less pronounced dampening of the isotope signal. A fairly large range in the isotope signal was measured also in samples from Mrzlek spring, however, the large variability can in this case be attributed to a stronger influence of the Soča river and the fact that Soča river water is more enriched in the heavier carbon isotope (Fig. 5.36). During surface flow, isotope exchange between the DIC and atmospheric carbon takes place. Because atmospheric carbon is enriched in the heavier carbon isotope, a change towards the more positive values can be expected. Most of the samples for the 7"' SWT project were taken from springs, yet some of them were also taken from lower course of surface flow, e.g. from streams on flysch rocks and from river Soča. In order to evaluate the scope of isotope exchange, sampling was carried out along the Bela stream above VIPAVA Jan-93 Apr-93 Jui-93 Oct-93 Jan-94 Apr-94 Jul-94 Oct-94 Jan-95 Apr-95 Jul-95 Date 13C-DIC o Alkalinity Fig._ 5.34: Carbon isotope composition and alkalinity of Vipava spring. PODROTEJA -6 -7 -- -9 --£-10 -- o 1, I CO -12 + -13 -- 1 -14 ^ -15 - -16 Jan-93 -4,5 -4 __^ CT -3 NNNNNNN aicotDoicocdoico (NOOO'-'r-^CM Fig. 6.2: Comparison of the Hubelj discharge behaviour during the second tracing experiment in April 1994 with the characteristic discharges (gauging profile Hubelj -Ajdovščina). Measured Hubelj discharge at the time of injection in Belo Brezno (October 14, 1993, 13:00) was Q.= 2.786 mVs. The following discharge data (Q in mVs) was evaluated: Oct 14 to Dec 31, 1993 Oct 14 to Nov 13, 1993 long-time (1961-1990) Q 1993 ^mean Q Q ^mean Q ^max 1.085 5.73 34.59 2.11 6.77 2914 0.382 3.03 5950 Oct Nov Dec average 10.1 7.64 5.11 7.6 3.58 4.19 3.51 3.76 6.2.2. The Hubelj Spring in the Time of the Second Tracing Experiment (April 16 to July 31, 1994) The values of discharges of the Hubelj were below average in the time of tracing experiment, if compared to the average over many years for the same period (April, May, June, July 1961-90). The mean discharge amounted to 2.08 mVsec in the time of tracing experiment and was by one third lower than the mean discharge of the period. The lowest discharge of 0.29 mVsec was only one quarter of the mean of extremes of the minimum low discharges in the period, and the highest discharge of 31.27 mVsec exceeded by 2-times and a half the mean of extremes of the maximum high discharges in the period. At the injection of the tracer on April 16, 1994, the initial discharge of 5.409 mVsec was higher than the mean discharge of the period and it was higher by 5-times than the mean discharge in the time of tracing experiment. THE HUBELJ HOURLY DISCHARGES 1994 lltllf I 2 S 2 S E;; - 0,1 0 ^pr 94) ft j ^ ' fd iJOj 1 \ A 3(4ugö5) - - ^^, ^ i-- 25 50 75 time after inaction [d] 0,6 0.5 0,4 cn E 0,3 OH 3 0,2 in o> 0,1 0 100 0,200 <5-0,150 Ol -0,100 CO ^ 0,050 0,000 (Oct 93) i sjAug 95) I ■ ......... i i <2 Api j 94) 1 i j i jl... M/V^i 0,020 0,015 "a E, 0,010 a ih ro 0,005 S 0,000 25 50 75 time after injection [d] 100 Fig. 6.19: Comparison of the uranine breakthrough in the Hubelj spring for the three repeated injections in the ice cave Belo Brezno in 1993, 1994 and 1995. The ice cave Belo Brezno, the injection point for repeated uranine tracing under different hydrologic conditions in the central part of the Trnovski Gozd plateau, is developed in the limestones of the Trnovo nappe. Following the general SW dip of the Uppertriassic, Jurassic and Cretaceous carbonate rocks of the Trnovo nappe, directed by the mainly NW-SE striking strike slip faults main reoccurrence of the tracer injected in Belo Brezno is the karst spring Mrzlek at the deepest regional base level of the karst groundwater. During all hydrologic situations tested the Mrzlek spring was the main outlet. A direct comparison of the breakthrough curves resulting from the three uranine injections in experiments is given in Figs. 6.18 and 6.19. Caused by the flooding of the spring outlet by the Soča river due to the construction of the Solkan hydropower plant, no current discharge measurements are available. Based on a mean discharge calculated from existing long-term observations from 1960 to 1990 the recovery was roughly estimated. 6.3.3. Results of the Vipava Area 6.3.3.1. The Second Tracing Experiment in Spring 1994 (H. BEHRENS, R. BENISCHKE, W. KÄSS, M. ZUPAN) From the individual sampling stations at the Vipava springs the samples have been delivered in different packages (Tab. 6.5). After analysis of a first series of samples some promising results showed a steep but smooth increase of the concentrations. So it could be expected for the first moment that this was a beginning of a rather classical breakthrough curve. But in the samples of the following series the pattern of breakthrough was quite different and brought concentrations for all sampling stations that could be interpreted in many different ways (influence of biological, chemical or photochemical decay, hydrological events, analytical errors and so on). The most likely interpretation is, that the samples have been influenced by some decay or adsorption processes. During evaluation and comparison of the results from the different outlets it became apparent, that a component separation based on the data of the artificial tracer would lead to unreliable results, especially for those, where the concentration values of Vipava 4/8 (the total runoff) were higher then those of the individual springs. This is impossible, because any mixing can result at the best in the same concentration as it can be observed in the springs (Fig. 6.20). The breakthrough-curve shows in the beginning a normal increase and is not influenced by secondary discharge peaks, also the discharge peak at approx. 500 h after injection had no influence on the concentration. The strong discharge pulse on 19th of May caused a new concentration peak, showing that the tracer which remained obviously in the system until that time has been washed out. From this time on only a decrease in concentration could be observed until the end of the sampling program. The shape of the first concentration peak cannot be explained by special hydraulic influences from subsystems of the Vipava aquifer, because there is no indication in the discharge curve. Irregular changes or fluctuations in the time-concentration graph a short time after the main peak and a significant concentration dropdown (approx. 300 h after injection) may be a hint on other than hydraulic influences. Possible explanations will be given later in this section. With exception of station Vipava 4/8 no other spring was equipped for continuous recording of discharge or stage, only Vipava 4/6 and Vipava 4/7 were measured at a bridge of their joint runoff channel about 100 m downstream of the outlets. This was a pity insofar that there was no other possibility to compare the tracer breakthrough curves at the springs with their individual discharge. Before the tracing experiment it was known from hydro-chemical analyses and conductivity measurements that the most northern spring T I 2D 18 16 1>t 12 10 \ g v 1 6 k \ 4 1 o A 0 ^---- /u 2m 4D «D 8CD 1he I" r s 8 L 4 2 O \ \ J 1 1 ^ an 4D eoo 11mn^li(ecllcn aoD 120 Fig. 6.25: Second experiment, April 1994: Breakthrough curve of Uranine at Vipava 4/5 (Pod Skalo). KÄSS (ref. to chapter 8.1.) could be irregular adsorption at the walls in the sample flasks, or it is a combined influence of both adsorption and biodegra-dation. Summarising the characteristic data from all breakthrough-curves it can be said that the first arrival and therefore the maximum flow velocity is quite similar for all stations (Tab. 6.14). The data for peak concentration and the flow velocity calculated for the concentration peak are very influenced by the above mentioned irregularities in the concentrations; they depend on the degree of possible degradation effects. Despite these influences the calculated recovery for Vipava 4/8 (the only station where discharge data were available) is rather high. But a recovery of about 74 % means that approx. 25 % remained in the system until the end of the sampling program. But taking into account, that the measured concentration values are the result from unknown effects mentioned above, the total recovery could also be nearly 90 or 100 %. Attempts to separate runoff components only by the uranine data failed. Corresponding concentration values could not be compared in the strong mathematical sense and for separating the discharge of Vipava 4/6 and Vipava 4/7 from Vipava 4/8 was not possible by means of the uranine data, because there was no sampling station at the gauging section for Vipava 4/6 and 4/7. Tab. 6.14: Summary of tracer data from all sampling stations. Injection Start Injection End Hor. Distance Vert. Difference 1994.04.16/12:45 1994.04.16/ 12:50 12990 365 Tracer: Amount (gross;kg): Reference (net;kg): Amount (net;kg): Uranine 7.000000 0.004228 6.995772 Spring Date/Time Flow time after inj. start (h) Flow velocit y(m/h) Conc. (mg/m^) Std. Conc. (m-=) Load (mg/s) Vipava 4/1 (Pri Kapelici) 1. Arrival 1994.04.19 14:00 73.25 177.3 0013 0.186 Peak 1994.04.23 10:00 165.25 78.6 0.939 13.429 Vipava 4/2 (Pod Lipo) 1. Aiiival 1994.04.19 15:00 74.25 174.9 0013 0.187 Peak 1994.04.23 11:00 166.25 78.1 1.305 18.654 Vipava 4/3,(Perhavčeva Klet) 1. Arrival 1994.04.19 11:00 7025 184.9 0.008 0.119 Peak 1994.04.20 09:00 92.25 1408 1.467 20.975 Vipava 4/4 (Vipavska Jama) 1. Arrival 1994.04.19 14:30 73.75 176.1 0.065 0.929 Peak 1994.04.22 08:00 139.25 93.3 1.512 21.614 Vipava 4/5 (Pod Skalo) 1. Arrival 1994.04.19 14:30 73.75 176.1 0.048 0.686 Peak 1994.04.22 08:00 13925 93.3 1.258 17.986 Vipava 4/6 (Pod Farovžem A) 1. Arrival 1994.04.19 14:30 73.75 176.1 0054 0.771 Peak 1994.04.22 08:00 139.25 93.3 1.219 17.429 Vipava 4/7 (Pod Farovžem B) 1. Arrival 1994.04.1911:00 70.25 184.9 0.001 0.014 Peak 1994.04.19 21:00 80.25 161.9 0.074 1.059 Vipava 4/8 1. Arrival 1994.04.19 10:00 69.25 187.6 0.005 0.067 0091 Peak 1994.04.20 20:00 103.25 125.8 1.455 20.796 13.963 Load - peak conc. 1994.04.20 20:00 13.963 Peak load at: 1994.04.20 18:00 14.121 Recovery until: 1994.07.28 09:00 5.14 kg Recovery until: 1994.07.28 09:00 73.46 % 6.3.3.2. The Fourth TVacing Experiment in Autumn 1995 (M. ZUPAN) The last tracing experiment in the framework of the program was performed during prevailing low water condition. It was a repetition of the tracing experiment in spring 1994 (Chapter 6.3.3.1) with the injection of pyranine to the Lokva stream below the Predjama castle. Additional a second injection point was chosen on the central Nanos Plateau, the pothole Slapenski ledenik (Chapter 2.5) to get information about the vertical water flow from Nanos towards the Vipava springs. Here uranine was injected (Tab. 6.1). Pyranine Astonishingly, the dye tracer pyranine was not at all detected. One possibility could be a dramatic change in the hydrogeological situation, respectively in the flow directions, in the catchment area of the Vipava depending on the hydrologic situation. While by prevailing high water conditions the water from the sinking stream Lokva is directed more or less directly to the Vipava spring as proved by a recovery rate of about 74 % in spring 1994 (compare Chapter 6.3.3.1), the flow direction during low water conditions as in autumn 1995 could change towards Timava. Hence no sampling was carried out which could prove this hypothesis, it is still pure speculation. Beside the hydrogeological conditions of the catchment area the various possibilities of biological, chemical or photochemical decay, which can destroy completely pyranine (ICäss 1992), have to be taken into account. The tracer amount injected was with 8 kg pyranine almost in the same range as in spring 1994 (7 kg uranine), when dilution was higher due to the high water conditions. Therefore a high dilution of the tracer pyranine below detection limit can be excluded. Uranine Uranine appeared in all three Vipava springs, which were chosen for the observation. The times of the first uranine appearing and the time of the maximal concentration are close together (Tab. 6.15). The concentration curves of the Vipava 4/2 (Fig. 6.28) and 4/5 (Fig. 6.29) are very similar, while the curve of the Vipava 4/7 (Fig. 6.30) is periodical different. These results prove once more the assumption that the various Vipava springs have different catchment areas, which are influenced by the hydrologic condition. 0,180 „0,160 0,140 °>0,120 i.0,100 ® 0,080 E 0,060 2 0,040 0,020 0,000 Sampling point: VIPAVA 4/2 26.10.95-30.5.96 o o CM § S CM P5 to CO o o s 8 8 8 § ? Time (h) Fig. 6.28: Fourth experiment, October 1995: The concentration curve of uranine in the spring Vipava 412. Fig. 6.29: Fourth experiment, October 1995: The concentration curve of uranine in the spring Vipava 415 point: VIPAVA 26.10.95-25.5.^ -wamne r»ne(h) QVip(4/6+4/7XiB3/s) Tab. 6.15: Overview of relevant parameters derived from the uranine breakthrough in the Vipava springs 5/5 and 417 in the fourth tracing test in autumn 1995 (injection into the pothole Slapenski ledenik, Oct 10, 1995): time(t^^^), concentration (C) and velocity of the first appearance, time of maximal concentration (^max)> fnaximal concentration (C^^J and dominant velocity (v^^J in the springs and the recovery (R). Spring C [mg/m ^max [h] Vmax [m/h] Cmax [mg/m tdom [h] Vdom [m/h] R [kg] R [%] Vipava-4/5 0,0015 406 19,7 0,1794 502 15,9 1,412* 1) 28,2 Vipava-4/7 0,0011 405 19,7 0,1457 503 15,9 0,233* 2) 4,66 +1) = recovery rate calculated for 4/1 and 4/5 +2) = recovery rate calculated for 4/6 and 4/7 6.3.4. The decomposition of tracers in the spring waters (M. ZUPAN) The decomposition of the uranine is different in different types of water (BEHRENS & ZUPAN 1976; ZUPAN 1991). To estimate this characteristic the analyses of limited number of samples taken in spring Hubelj and Vipava was repeated. The concentration of uranine in the samples taken in the spring Hubelj from October 22, 1993, till October 30, 1993, was determined for the first time from October, 28 till November 16, 1993. We repeated the uranine analysis in 89 of the mentioned samples in February 1994. The differences between the two determinations were in the interval of analytical repeatability and the concentrations of the second determination were practically the same as of the first one. During the 4"" tracing experiment (compare Chapter 6.3.3.2) we stored consecutive samples of the spring Vipava one in a glass flask and the second in a plastic flask. The samples in the glass flasks were analysed in maximal 10 days after sampling. Because of the lack of the time, the samples stored in the plastic flasks were analysed not before January, 25, 1995. The measured concentration of uranine in the consecutive samples was significant lower in the samples stored in plastic flasks then the concentration of the samples stored in the glass flasks. The difference between two consecutive samples decreased 15 to 100 % and in the next sample stored in the glass flask increased again in the same percentage spread. Repeated analyses of 33 samples of the Vipava spring 4/2 taken from November, 13, 1995 till November, 21, 1995 was performed. The decrease of the uranine concentration of the samples stored in glass flasks ranges between 1 and 9 %, while the decrease in the uranine concentration of the samples stored in the plastic flask was 3 to 100 %. Therefore in calculating of the tracer recovery for the 4"' tracing experiment we considered only the concentrations measured in the samples stored in the glass flasks. 6.3.5. The Background Concentrations of the Used Fluorescent Dyes (M. ZUPAN) Most of the spring water in the investigation area is used for water supply and therefore the number of appropriate tracers was very limited. Only the use of two fluorescent dyes, uranine and pyranine, was permitted. Additional the time intervals between the tracing tests were relatively short. Therefore we measured a great number of samples to estimate the background concentration in the springs. As background samples we took into account all intermediate samples between two consecutive tracing experiments. In Tab. 6.16 the number of measured samples and the concentrations were shown. Beside the dyes used in the tracing test we determined some signals at the characteristic wavelengths for other fluorescent dyes. During the first tracing experiment emission peaks with maximal wavelength, significant for eosine appeared in the samples of the Hubelj spring. We evaluated these peaks according to the calibration curves of eosine. It would be possible that they belong to compounds of an unknown source. Eosine we determined in 88 samples taken from November 2, 1993, to February 18, 1994. The measured concentrations were 0.010 - 0.115 mg/m^. Tab. 6.16.: Minimal and maximal background concentrations of fluorescent dyes in the springs in the investigation period. Minimal and maximal concentration of fluorescent dye - mg/m' Spring Year Number of samples uranine pyranine eosine ifaodamine Hubelj 1993 27 udl»- 0.001 (2) udl udl udl 1994 52 udl-0.002(2) udl udl udl 1995 50 udl udl-0.04(1) udl udl-0.007 (1) Vipava 1993 40 udl - 0.001 (2) udl udl udl-0.002(1) 1994 51 udl udl-0.04 (2) udl udl-0.005(1) 1995 53 udl udl udl udl Mrelek 1993 9 udl udl udl udl 1994 10 udl udl - 0.04 (1) udl udl 1995 5 udl udl udl udl Podroteja 1993 9 udl udl udl udl 1994 10 udl - 0.005 (2) udl udl udl 1995 5 udl udl udl udl Bela 1993 3 udl udl udl udl 1994 10 udl udl udl udl 1995 5 udl udl udl udl Belščica 1993 3 udl udl udl udl 1994 10 udl udl udl udl 1995 5 udl udl udl udl Hotešk 1993 8 udl udl udl udl 1994 10 udl-0.006(1) udl - 0.03 (1) udl udl 1995 5 udl udl udl udl Kajža 1993 8 udl udl udl udl 1994 10 udl udl udl udl 1995 5 udl udl udl udl Prelesje 1993 9 udl-0.029(1) udl udl udl 1994 10 udl - 0.037 (1) udl udl udl 1995 5 udl udl udl udl udi = mder detection limit (1) = number of samples which contained the dye 6.4. RESULTS WITH PHAGES (M BRICELJ) 6.4.1. Introduction Phage P22H5 was first introduced in Greece (BRICELJ et al. 1986) in a combined tracing experiment on the Central and Eastern part of Peloponnesus. The phage of mouse typhoid bacterium was chosen because the phages of Salmonella typhimurium had been rarely encountered in surface waters (SEELEY & PRIMROSE 1982). In such manner, high background coliphage titres, usually encountered in natural polluted waters, that can interfere with tracer curve, could be avoided (ALTHAUS et al. 1986). Phage P22H5 is clear plaque mutant of transducing phage P22 (SMITH & LEVINE 1967) and produces very discernible clear plaques in the lawn of growing host bacteria. Besides this feature, P22H5 phage (Podoviridae) could be propagated to high titres in controlled growing conditions (BRICELJ 1994). During several tracing experiments in the Slovenian karst region (KRIVIC et al. 1987; KRIVIC et al. 1989; HABIČ et al. 1990) and in a tracing experiment in the Styrian karst near Graz (BEHRENS et al. 1992) in ten tracing experiments only once the background for salmonella phage was positive, but only in some samples. The phage P22H5 proved to be a better tracing agent in comparison to coliphage T7 in several deactivating experiments at the air-water interface (BRICELJ & ŠIŠKO 1992) and in recovery experiments of clay mineral adsorption tests (BRICELJ 1994). 6.4.2. Injection data The phage tracer - P22H5 virulent mutant of host bacterium Salmonella typhimurium LT2 (TL474 w.t.) - was injected, subsequently three times at the location Zavrhovc - Otlica 88, which is a kilometre away from the Hubelj spring on the plateau below Črni Vrh. In the first tracing experiment a hole with the diameter of 5 cm was drilled in the floor of the doline, 5.5 m deep into permeable strata. Before the injection, 1.5 m^ of water was poured into the drilUng hole, following with 16,500 ml of phage broth that were subsequently washed with additional 3.5 m' of water. The injection of phage tracer began at 14.25 on 14 October, 1993 and was continuing for 3 minutes. The total concentration of injected phage particles was 3.0 x 10'^ pfu (= 1.84 x 10» pfu /ml x 16,500 ml). The second injection place for the phage tracer lied in other doline next to the place of the first injection. The injection of lithium and phage tracer took place on 16 April, 1994. A fissure at the bottom of the dohne, was first washed with 3.5 m^ of water, from 10.20 to 10.25 hthium chloride in quantity of 110 1 (30 kg) was poured into the fissure, followed by the washing of 1.0 m" of water. From 10.29 to 10.30 phage tracer in the quantity of 20,500 ml was poured and then washed with 3.0 m^ of water. The total quantity of phage tracer was 3.75 x 10'^ pfu ( = 1.83 x 10" pfu/ml x 20,500 ml). The place of the third injection of phage tracer was equal to the second one. On the 1 August, 1995 the phage tracer in quantity of 26,000 ml was poured into the same fissure, at the bottom of the doline. Injection began with the washing of the fissure with 3.5 m^ of water at 10.21. Between 10.25 and 10.28 phage tracer was poured into fissure, followed by washing with additional 3.5 m' of water. The total quantity of phage tracer was 6.6. x 10'^ pfu (= 2.52 X 10" pfu/ml x 26,000 ml). 6.4.3. Results The relevant parameters derived from all three experiments with the phage tracer P22H5 are summarised in the tables Tab. 6.17, 6.18 and 6.19. In the first tracing experiments with phage tracer P22H5 the samples for the determination of phages were taken at samphng points Hubelj, Skuk, Gorenje Studenec, Lijak, Mrzlek and Hotešk. The phage tracer reappeared only in the Hubelj spring (Fig. 6.31). The first positive result was evaluated on October 16, 1993 at 07.02 as 0.6 pfu/ml. Maximum concentration 32.4 pfu/ml was determined in the sample from October 17, 1993 at 11.02. On November 4, 1993 there was the last positive resuh of 0.4 pfu ml at 23.00. The sampling was stopped on November 13 after several negative results. 30 - 25 70 IS ^ ! 10 5 W K 200 2S) 300 «tee fem iqectiai 350 400 4S) 500 l4i«ge -«ntoflcmt The recovery of tracer was 0.78 %. The gravity centre position of tracer curve t, was calculated to 94.32 hours. The empirical formula = a * tj,..^^ * Q = quantity of tracer needed in tracing experiment; a = deactivation factor; t^^.^^ = time of tracer travel in sec; Q = waterflow in ml/s; Q was taken as average waterflow, including the data from the first appearance of tracer, to the last positive result) was used to calculate the needed quantity of phage tracer for a = 1, Q = 27.79 m3/s and t^^.^^ = 94.7 h. The resultant quantity was 9.5 x 10'^ pfu. The quantity injected was 3.0 x 10'^ pfu, therefore the calculated inactivation factor is in the magnitude of 316.6. The real inactivation factor calculated from the recovery value 2.43 x 10'^' was 128.0, that means 2.8 times lower than the calculated one. Concerning the negative values of control samples, negative background of salmonella phage, sufficient quantity of phage tracer and flowthrough curve of the reappearing tracer, the conclusion could be, that the connection between drill hole in the doline at Zavrhovc and the Hubelj spring does exist. In the second tracing experiment in spring 1994, the samples for the determination of phage were collected only in the springs of Gorenje Studenec, Skuk and Hubelj. The first positive result was evaluated after 54.30 hours on 18 April, 1994 as 0.5 pfu ml. The maximum value of 1.1 pfu ml 1 was determined on the same day, between 21.00 and 23.00 hours. The last positive result was determined on 25 April, 1994 found in the sample at 01.00 hour (Fig. 6.32). 100 150 time torn i^jectai (h) Mg/1 tg Uttdwi pflitol tgiAi«g« The recovery of tracer was 0.012 %. The gravity centre position of tracer curve t^ was calculated to 99.61 hours. The resultant quantity for empirically calculated tracer quantity that we need in the case of a = 1, Q = 4.38 mVs and = 99.61 h was 1.57 x 10'^ pfu. The injected quantity was 3.7 x 10'= pfu, so the calculated inactivation factor is in the magnitude of 2,354.6. The real inactivation factor calculated from recovery value 4.45 x 10" is 8,314.6, that means about 3.53 times greater than the calculated one. In the third tracing experiment, in the summer of 1995, the samples for the determination of phage were collected only in the spring of Hubelj. The first positive result was evaluated almost after one month, on August 29, 1995 at 00.00 hours as 0.5 pfu/ml. The maximum value of 1.0 pfu/ml was evaluated on the same day at 12.00 hours. The last positive result as 0.1 pfu ml determined on August 31 at 00.00 hours. The additional positive value was recovered from the sample taken on September 11 at 06.00. The value of the determined phage was 0.2 pfu/ml. The recovery of tracer was 0.001 %. The gravity centre position of tracer curve t^ was calculated as 678.2 hours. The resultant quantity for empirically calculated tracer quantity in the case of a = 1, Q = 3.19 mVs and t = 678.2 h was 7.8 X 10" pfu. The injected quantity was 6.6 x 10" pfu, therefore the calculated inactivation factor is in the magnitude of 846.4. The real inactivation factor, calculated from the recovery value 4.62 x 10" is 16.9 times greater than the calculated one. Tab. 6.19: Measured and calculated data for the three tracing experiments with phage tracer P22H5, injected at the location Zavrhovc, a = deactivation factor calculated from injected and recovery values; av. precipit. = average precipitation in the month period before the injection of phage took place; av. Q inj. = average day's throughflow in the time of injection of tracer; max. con. Q = Q value at the peak concentration of tracer curve; recovery = calculated recovery of the phage tracer from injected and recovered quantity of phage tracer. a av. precipit. av. Qinj. max.conc. Q recovery October 1993 128.0 15.4 mm 2.81 m^/s 2.90 mVs 0.78 % April 1994 8314.6 11.8 mm 6.33 mVs 9.21 m^/s 0.012 % August 1995 1.0 X 10 2.8 mm 0.51 mVs 9.50 mVs 0.007 % Tab. 6.17: The values of the time of appearance of phage tracer and its velocity in the spring of Hubelj for three tracing experiments. The distance between the injection point and the sampling point suits 1000 m for each tracing experiment: t^^.^^ - time elapsed from injection and the first appearance of tracer, t^^^^ = time elapsed from injection and the maximal quantity of tracer; t^ = time calculated from following equation Z ci*ti / £ ci; = velocity calculated with t^^.j = velocity calculated with t^. ^max ~ velocity calculated with ? V ma^ Ig tmin Vmin tmax vmax tg Vtg Octob er 1993 40.61 h 0.007 m/sec 592.2 - m/day 68.62 h 0.004 m/sec 350.5 m/day 94.7 h 0.003 m/sec 253.9 m/day April 1994 54.50 h 0.005 m/sec 442.9 m/day 59.30 h 0.005 m/sec 405.5 m/day 99.61 h 0.003 m/sec 241.4 m/day Augus t 1995 661.5 h 0.0004 m/sec 36.4 m/day 673.5 h 0.0004 m/sec 35.7 m/day 678.2 h 0.0004 m/sec 35.5 m/day Tab. 6.18: Comparison of the determined parameters of the phage and the lithium (Chapter 6.5) breakthrough in the Hubelj during the second tracer experiment in April 1994. (explanation of the abbreviations, are given in Tab. 6.17). Tracer. ^min Vmin ^max vmax tg vtg phage P22H5 50.5 h 0.0051 m/sec 59.5 h 0.0046 m/sec 99.61 0.0028 m/sec 442.9 m/day 405.5 m/day n 241.4 m/day lithiu m 82.5 h 0.005 m/sec 98.5 h 0.0028 m/sec 1265 h 0.0022 m/sec 442.9 m/day 244.1 m/day 190.1 m/day 6.4.4. Conclusions The tracing experiments with phage P22H5 and other tracers on the karst plateau were performed in three different water level situations, low, high and medium. The first tracing experiment was performed in the medium level of water in the spring of Hubelj (compare Chapter 6.2.1). The medium day's water level in the time of injection, was 2.81 mVs. The average precipitation in the month period before the injection was 15.4 mm (Tab. 6.19). It is beheved, that the underground passages under the permeable strata in the bottom of doline were partly saturated by water, after the steady raining, before the tracing experiment took place. In such conditions the bacteriophage tracer was injected to the permeable strata for the first time instead of directly into the water as was commonly done in preceding experiments in several karst locations (Tab. 6.20). The recovery of tracer in the first experiment was the highest comparison to the recovery values of the two subsequent tracer experiments (Tab. 6.17), although a part of phage tracer was adsorbed to the underground surfaces. This can obviously be seen in the breakthrough curve of phage tracer at the Hubelj spring (Fig. 6.31), where the second peak of phage tracer with 9.2 pfu/ml in 180.6 hours after the injections strictly follows the sudden augmentation of water throughflow at the Hubelj spring. Second tracing experiment was performed after the melting of the snow, which gave high water with the average day's throughflow of 6.33 m^s in the time of the injection. The recovery of the phage tracer was lower than in the first tracing experiments because of the high dilution of phage tracer and possible dispersion of the phage tracer in highly saturated strata, away from the main flow. The difference in the values of deactivation factor in both experiments could be contributed to the dispersion of the phage tracer rather than to the enhanced adsorption. The effect of lithium chloride on phage tracer could not be omitted, but we think that because of the high dilution the effect of lithium tracer on phage is of less importance. Nevertheless, the velocity of phage tracer calculated from the centre of the gravity of tracer curve was a little bit lower than in the first tracing experiment (Tab. 6.17). The gravity values of tracer curves from the both mentioned tracing experiments have a difference about five hours (Tab. 6.17). The difference could be contributed to the different injection locations or different underground water conditions. Comparing the phage reappearance data of the second tracing experiment with the data of lithium that was injected in the same location simultaneously (Tab. 6.18 and Fig. 6.31), we can conclude that the phage tracer preceded the lithium for approximately one day (26.9 h). The first appearance of the phage tracer occurred on 18 April at 17.00 (54.5 hours after injection) and from the smoothed curve of hthium tracer we can conclude, that first appearance of lithium occurred on 19 April, at 17.00 (82.5 hours after the injection). The difference in recovery quantity of both tracers is very high. comparing 1.69 % of lithium with 0.012 % of phage. This difference could be contributed to water level conditions and velocity of both tracers. The phage that was quicker in moving towards Hubelj area was probably more diluted on April, 18 when the through-flow augmented from 7.5 m sec (17 April) to 12.56 m sec than lithium that appeared on 19 April, when the throughflow at Hubelj lowered to 6.92 m sec. Completely different conditions were in the time of the third tracing experiment, when the average precipitation in the monthly period before the injection was only 2.8 mm (Tab. 6.19). The phage tracer that was injected on 1st August and washed into the permeable strata with water, remained there immobile, or moved very slowly for nearly a period of a month. The high water level, which is indicated by the sudden augmentation of throughflow from 0.52 mVs (27 of August) to 13.03 m'/s pushed the adsorbed and extremely slowly moving phages into the Hubelj spring., where the peak of tracer curve occurred on 29 August at 12.00. Recovery value of 0.001 % could be contributed partly to the deactivation of adsorption to different underground surfaces and partly to dilution of phage tracer because of the sudden augmentation of the ground water levels. Keeping in mind the time of the passage of phage tracer in first and second tracing experiment, that was 94.7 and 99.6 hours respectively and the day values of precipitation at Otlica in the time of reappearance of phage tracer; we can conclude that the main water which pushed the phages into the Hubelj spring came from other direction than from the background of Otlica, where the precipitation achieved the maximum values on 29 August with 98.5 mm in the time when the peak value of phage tracer in the Hubelj spring was already determined. The recovery values for phage tracer P22H5 in both three experiments at Nanos plateau are for several magnitudes lower than in the preceding tracing experiments in different karst regions, where bacteriophage was injected directly into flowing waters (Tab. 6.20). Nevertheless, the results of all the three tracing experiments with the phage P22H5 on high karst plateau confirm, that the phage tracer could also be injected into permeable strata with additional washing, where the water flow doesn't occur. The best recovery values for phage tracer can be expected, when permeable strata are sufficiently saturated due to longer rainy periods. Tab. 6.20: The centre of gravity values (tj, and average velocity of phage tracer based on value for several tracing experiments with P22H5 phage in karst environment. Recovery values for some tracing experiments are also included. injection point sampling point distance [m] t« [h] Vtg [m/day] recovery [%] Kapsia Kiveri 39,000 233.0 4017 - Smokavska vala Rižana 3880 348.0 268 0.006 Hotičina Rižana 12,450 482.0 620 4.5 Lurbach Hammerb ach 3000 53.4 1348 2.5 Kačji potok Radeščica 19,200 511.4 901 3.0 Kačji potok Obrh 20,000 704.6 681 - Bajer Krupa 6000 99.1 1453 - Vrčice Krupa 6000 156.8 818 - Movražka vala Ara 800 80.8 237 - Movražka vala Mlini 1000 94.6 165 3.4 Movražka vala Sopot 1043 145.1 173 - Zavrhovc Hubelj 1002 94.7 255 0.78 Zavrhovc Hubelj 1002 99.61 247 0.012 Zavrhovc Hubelj 1002 678.2 36 0.007 6.5. RESULTS WITH SALTS (W KÄSS) 6.5.1. Lithium IVacing Test at Zavrhovc (April 16, 1994) The kation lithium was used as a tracer together with bacteriophages (compare chapter 6.4) in the second tracing experiment in spring 1994. As briefly described in chapter 6.1 (Tab. 6.1) the injection of 30 kg lithium chloride solved in 110 1 of water took place on April 16, 1994 at 10:25 and was followed by the injection of 20.5 1 phage suspension at 10:30 (compare chapter 6.4) in the rocky doline below the Zavrhovc farm. The salt suspension was rinsed down with about 1 m' water. After flushing of both tracer injections was performed with 3.5 m-'' water. As observation points for lithium the spring Hubelj (altitude: 240 m a.s.l.) and the two smaller karst springs in the vicinity of the Hubelj spring, Gorenje (243 m a.s.l.) and Skuk (520 m a.s.l.) were chosen. Results Hubelj Between April 16, 13:00 and May 25, 1:00 the total of 232 samples were investigated. The extremely low background between 0.01 and 0.04 /xg/l allowed a good recognition of influences from the tracing, even when they were very low. Between April 20 and 26 a significant Li-increase above the background could be detected (Fig. 6.33). For the interpretation the background was subtracted (net-values for the increase above the background) and the breakthrough-curve between April 19, 1:00 and April 27, 23:00 was fivefold smoothed (Fig. 6.34). The injected 30 kg LiCl only contain 16.4 %, resp. 4.92 kg lithium. By means of the discharge values, made available by Hydrometeoroloski Zavod, Ljubljana, a recovery of 70.52 g lithium was calculated for the lithium passage during the period above given. These are only 1.43 % of the injected quantity. A second Li-passage took place between May 19 and the end of the observation on May 25, 1:00. This passage was aroused by heavy rainfalls which caused a discharge of the Hubelj-spring up to 31,600 1/s (Tab. 6.21): A rough calculation of this second lithium passage between May 19, 13:00 and May 25, 1:00 resulted in an additional lithium recovery of 81.95 g. Thus 152.7 g lithium, resp. 3.1 % reappeared completely with this test in the spring Hubelj. In Fig. 6.35 the cast-line for the whole observation time is depicted. 16.04.94 21.04.94 26.04,94 01.05.94 06,05.94 11,05.94 16,05.94 21.05.94 26.05.94 Date -Lithium ------Discharge Fig. 6.33: Second tracing experiment: analysed lithium-values in the spring Hubelj in connection with the discharge of the Hubelj (m^/s). 0,16- ____ 0,14 "o) E 0,12- 0,1- Ö) o v_ o 0,08- E 0,06- E =j 0,04- x: 3 0,02 0 19.04.94 21.04.94 23.04.94 25.Ö4.94 Date 27.04.94 29.04.94 Lithium Fig. 6.34: Lithium-netto-values in the Hubelj spring between April 19 and 27. Tab. 6.21: Lithium passage in the spring Hubelj between May 19 and 25 due to a significant increase in the discharge. l>ay Time Li iu^h Oi^Vs) 18.5.1994 13:00 0.01 677 18.5.1994 19:00 0.01 677 19.5.1994 1:00 0.02 792 19.5.1994 7:00 0.01 4,220 19.5.1994 13:00 0.02 27,000 19.5.1994 17:00 not observed * 31,600 21.5.1994 1:00 0.04 20,500 21.5.1994 13:00 0.03 13,100 22.5.1994 1.00 0.05 22.5.1994 13:00 0.05 6,130 23.5.1994 1:00 0.02 5,060 23.5.1994 13:00 0.04 4,390 24.5.1994 1:00 0.03 3,910 24.5.1994 13:00 0.04 3,450 25.5.1994 1:00 0.05 3,170 * the sampling was interrupted because ot high water! 0.9- 0,8 0,7 I 0,6- E "'S' £ 0,4- 0,3- 0,2- 0,1 16.04.94 26.04.94 06.05.94 Date 16.05.94 26.05.94 Fig. 6.35: Cast-curve for the Li-breakthrough in the Hubelj spring. Gorenje and Skuk No lithium passage was observed at the other two observation points, Gorenje and Skuk. For the observation of a possible lithium breakthrough in the karst spring Gorenje 50 water samples were analysed for the observation period from April 16, 12:15 to May 24, 13:00. The highest Li-value observed was 0.11 /zg/l, the lowest 0.06 fig/l, with a medium value of 0.0866 /x.g/1. The standard deviation was 0.013 and the variance 0.00017. Period of observation: 16.4., 12:00 - 24.5., 13:00 with 51 samples. Highest Li-value: 0,08, lowest value: 0,04, medium value: 0,0586 jug/1. Standard deviation: 0,0088, variance: 0,000078. 6.5.2. Strontium Tracing Test at Mrzli log (April 16, 1994) A second salt injection was carried out with the kation strontium in the framework of the second combined tracing experiment. As injection point the deepest doline (784 m a.s.l.) of the karst depression Mrzli Log was selected (Fig. 6.1). The tracer solution consisted of 50 kg strontium chloride hexahy-drate, resp. 16.3 kg strontium, dissolved in 120 1 of water and 7 kg pyranine dissolved in 40 1 of water. The injection took place simultaneously at April 16 at 11:00 after a preflushing of the doline with about 1,000 1 and was followed by a after flushing of about 6,000 1. Main aim of this injection was to define the watershed between the Hubelj spring at the one side and the karst springs Podroteja and Divje Jezero at the other side (Fig. 6.1). Therefore 6 karst springs were selected as observation points for a possible strontium breakthrough (Tab. 6.22). Tab. 6.22: Observation points for a possible strontium recovery for the combined tracing experiment in Mrzli Log (April 16, 1994) with the distance from the injection point, the altitude of the spring outlet and the incline. Observation points Distance fm) Altitude (m a.s.l.) Incline 1 DIVJE JEZERO 7221 350 0.060 2 PODkO'l'EJA 7630 330 0.0595 3 VIPAVA 4/1 9594 99 0.0713 4 VIPAVA 4/7 9594 99 0.0713 5 GORENJE 10183 243 0.053 6 HUBELJ 925i 240 0.059 Results Divje Jezero Observation period: 19.4, 9:20 - 27.5., 18:25 Amount of samples: 44 Highest value: 31 jug/l Sr Lowest value: 18 ju,g/l Sr Medium value: 23 /ig/l Sr Standard deviation: 2,81 Variance: 7,9 Result: No Sr-passage Podroteja Observation period: 19.4, 9:25 - 20.7., 12:00 Amount of. samples: 51 Highest value: 45 ^tg/1 Sr Lowest value: 19 ^ig/1 Sr Result: The Sr-values constantly increased from the beginning to the end of observation (Fig. 6.36). Whether this has been influenced by the tracing, remains open. Fig. 6.36: Strontium values in the Podroteja spring. Vipava 4/1 (Kapelica) Observation period: 16.4, 10:00 - 28.7.,9.00 Amount of samples: 198 Highest value: 113 fig/l Sr Lowest value: 27 /zg/1 Sr Medium value: 49 ixg/l Sr Standard deviation: 17,8 Variance: 319 Result: The Sr-content constantly increased from the beginning to the end of the observation with some interruptions. Vipava 4/7 (Pod Farovžem-L.) Observation period: 16.4, 13:00 - 28.7.,9.00 Amount of samples: 198 Highest value: 113 ßg/l Sr Lowest value: 27 fig/l Sr Medium value: 49 /j,g/l Sr Standard deviation; 14,9 Variance: 221 Result: The Sr-content increased from the beginning to the end of the observation with distinct interruptions (Fig. 6.38). Fig. 6.38: Sr-contents in the spring Vipava 417 between April 16 and July 28. Gorenje Observation period: 16.4, 12:15 - 24.5., 13:50 Amount of samples: 50 Highest value: 19 fj,g/l Sr Lowest value: 9 /ig/l Sr Medium value: 13,5 /xg/l Sr Standard deviation: 1,88 Variance: 3,53 Result: No Sr-passage Hubelj Observation period: 16.4., 12:00 - 25.5., 1:00 Amount of samples: 232 Highest value: 9 fxg/\ Sr Lowest value: 2 fig/l Sr Medium value: 4,96 jjLg/\ Sr Standard deviation: 1,42 Variance 2,04 Result: No Sr-passage 6.6. MATHEMATICAL MODELING WITH THE MULTI-DISPERSION-MODEL (A. WERNER & P. MALOSZEWSKI) 6.6.1. Introduction Numerous tracer experiments have been carried out within the research program of the 7"'SWT on the Trnovski Gozd plateau (Slovenia). The area between the springs Mrzlek, Lijak and Hubelj (Fig. 6.1) formed one main focus of the investigations of the ATH. In the following the mathematical interpretation of the uranine tracer experiments of the input location Belo Brezno (Fig. 6.1, Tab. 6.1) will be described. At this place one tracer test was performed in each of the years 1993, 1994 and 1995 (compare chapter 6.3.2). Therefore it was possible to evaluate mathematically experiments with different hydrological boundary conditions. The main output was the karst spring Mrzlek in a distance of 19.8 km to the injection point and not the nearby located Hubelj spring (6.9 km distance). As described previously current discharge measurements of the Mrzlek spring are not available, due it's outlet in the dammed Soča river. 6.6.2. The Multi-Dispersions-Model (MDM) The Multi-Dispersion-Model (MDM) was used for the evaluation. This model was developed by MALOSZEWSKI et al. (1992) for the interpretation of tracer tests in Styria. The MDM is an extension of the classical convection-dispersion model after LENDA &. ZUBER (1970). The resulting breakthrough curve of a tracer experiment is seen as the outcome of different flow paths. Step by step the breakthrough curves of the individual flow paths and the parameter of convection (mean transit time) and dispersion (dispersivi^^y) processes are determined. The mathematical background of this model was illustrated detailed in the report of the SWT (MALOSZEWSKI et al. 1992). The following solution is vahd for every flow path: / N M, 471 p. = -exp \ t 1- V ^oj t [h (1) with C. = tracer concentration M = tracer mass Q = discharge t„ = mean transit time D a Pd= — = - VX X Pp = dispersion parameter D = dispersion v = mean flow velocity a = dispersivity i = index of the flow path The total concentration is the superposition of the individual flow paths: (2) i=l The discharge Q is normally necessary for a full calculation. Unfortunately this information was not available because of the location of the spring at the bottom of a river. However, it is possible to normalize the solution (1) to the maximal concentration. In the past the MDM was used for the interpretation of tracer tests in different karst areas (MALOSZEWSKI et al. 1994; BARCZEWSKI et al. 1996; LÖHNERT et al. 1996; WERNER et al. 1997a; 1997b). 6.6.3. The TVacer Tests of the Injection Place Belo Brezno Three different tracer experiments were selected for the mathematical interpretation. The ice cave Belo Brezno was the injection place for all of these tests. The injection was performed at the lowest point in this cave. An additionally injection of water should ensure that the tracer was flush out direct in the saturated zone. The experiments were carried out under the following hydrological conditions: Karst water level Number of Rain Events • 1993 very high many • 1994 high very few • 1995 very low no, first after 500 h The main outcome of the injected tracers was the Mrzlek spring. In the Hubelj spring it was only possible to detect very low concentrations with an episodic behavior (compare Chapter 6.3.2). A further detection of the uranine was only possible in the Lijak spring. The activity of this periodical spring strongly depend on the karst water levels. More details about the performance of the experiments, the sampling and the results are given in the chapters 6.1, 6.2 and 6.3. 6.6.3.1. The First Tracer Test (1993) This tracer test was carried out in the autumn 1993. The water level of the karst system was very high due to a longer precipitation period. The resulting breakthrough curve (Fig. 6.39) of the Mrzlek spring could be divided in different single peaks. However, these four peaks were not the result of the individual flow paths but of the multiple flow of one or two paths. Due to the high karst water level the tracer was transported very fast into the saturated zone. This leads to a quick transport. The less values for the dispersivity (Peak I and II) are typical for the transport in the conduit system of a karstic aquifer. However, a smaller part of the tracers was hold in the unsaturated zone and flush out a short time later by following rain events. The higher values for the dispersivity and mean transit times of the Peak III and IV show this behavior. Due to the high karst water level the Lijak spring was active during this tracer test. The determined values are comparable with the results for the Mrzlek spring. Therefore the Lijak drained probably the same part of the karst system. MRaLEK r>riO&3 ft — h. Peak3 v«y high karst wa» Iw^ Tiaoer 5 kg 10/14/1993 h m V[illlh] «itm] 222 89 35 272 73 28 359 SS 137 UJAK _ynmm_ I4*k fU l-L -nimiaai »"....... « -J multipteittteiMv Ttacer Skg • Date: 1W'W19»3 um 245 54 IS 381 35 49 572 35 122 «3 16 6S4 Fig. 6.39: Evaluation of the first tracing experiment from autumn 1993. 6.6.3.2. The Second Tracer Test (1994) This tracer experiment was also performed during high karst water levels, but after the injection no rain events were observed for the first 470 h (Fig. 6.40). A natural flush out of the tracer by the rain events like 1993 was not possible. The lower flow velocities and the higher values for the dispersivity (Peak 11) in comparison to the experiment of 1993 are the result of a delayed entry in the saturated zone. Because of the missing rain events the tracer was hold back in the unsaturated area. The following transport in the conduit system of the saturated zone is also very quickly. The third peak is caused by the rain events after 470 h. No tracer was detected in the Lijak spring because during the experiment the karst water level was decreased. The discharges of the Lijak spring were in the beginning about 5 ml/s and within two days they were fall down to values of less than 10 1/s. MRZLEK tiran ine n |'10E-3 mgflnT 2 Mnd« TtmeMa««li4KS<>n CrnicenliaiiM noE-3 me/ml i . e* . i mrOek / " \ \ / K/ V K aOP «9 500 Time sfler Injection Peak I Peak 2 Peak 3 Hydrrilogic Situation: hi^ karat watsa- levels until 470 h: no rain events ate470 h: several rain evajts Trace- Experiment Input: Belo Brezno Tracer; 5 kg lAanine Date: 04/16/1994 io[h] 307 393 502 v[iii/h] 64 50 39 OLlm] 495 44 71 Fig. 6.40: Evaluation of the second tracing experiment from spring 1994. MR21-EK Uranine ConeanlraSon flOe-S ms/nr^ 1 WIZM k -S Af u 6« SCO 1G00 1200 MOe 1600 TIraslh] «er Injealon Concantitfiiin [*10e.3 mgMl^ 1 Mtziek 1 ft hA ■. i W» 16W Time till aAerlniectioR Peak 1 Peak 2 Peak 3 Peak 4 Hydrologie Situation: • Very low karst water levels • Till 650 h: no intensive rain events • after 650 h: intenäve rain events Trac» Bxpo-iment • Input: Belo Bremo • Tracer: 7 kg Uranine • Date: 08/01/1995 to[h] vJniA] ai[m] 897 22 28 1046 19 22 1212 16 17 MRZLEK Uranine CoiK8nti;3tion [10E-3 mglnfl VT lime ^ter {{^ecson ConoBKMOB [lOE-s raBlinl Peak 1 Corrected interpretation: Effective Input afte 650 h 245 395 v[m/h] 81 50 OlW 299 222 1389 14 28 Peak 2 Fig. 6.41: Evaluation of the third tracing experiment of summer 1995. 6.6.3.3. The Third Tracer Test (1995) This experiment was carried out during a dry period in the summer of 1995. (Fig. 6.41)The karst water level was very low during the whole experiment. No larger rain events were detected during the first 650 h of this tracer test. The evaluation of the experiments (Fig. 6.42 above) shows great mean transit times but only very less dispersivity values. Therefore it can be assumed that the tracer was first hold in the epikarst. The following intensive rain events (after ca. 650 h) flush out the tracer into the saturated zone. The less dispersivity values show then the same transport behavior in the conduit system as in the years before. A fictive input after 650 h (28.8.) was simulated for comparison. The evaluation (Fig. 6.42 above) shows mean transit times in the order of the other experiments. The high dispersivity values are caused in the distribution of the tracer in the epikarst during the first hours. r I I 0.10 aos Ii « I 40 aw*............................................../igmiitiwn V ■"■i I - ---t'« 3ao7Äs^ 100 m) and the long mean transit times. The migration processes in the epikarst are also responsible for the episodic tracer detection in the Hubelj spring. A further quantitative evaluation is not possible because of the missing discharge values of the Mrzlek spring. The performed normalization can lead to deviations of the determined parameters. However, these differences are normally not very large (WERNER 1997). 7. CONCLUSIONS REGARDING THE INVESTIGATION AREA 7.1. UNDERGROUND CONNECTIONS IN DEPENDENCY TO HYDROGEOLOGICAL CONDITIONS (J JANEŽ) Geological cross-section 1-1' (Fig. 7.1) shows the structure, that makes the underground water flow from the western and middle part of Trnovski Gozd to the West, to the springs near the Soča river, possible. The whole area is part of the Trnovo nappe, where the Uppertriassic, Jurassic and Cretaceous carbonate rocks dip towards South-west. There is no hydrogeological barrier between Belo Brezno and the Soča valley. The Uppertriassic dolomite is found in the basis of karstified Mesozoic limestone. The dyeing in Belo Brezno likewise the older tracing test in Čepovan shows that the regional faults (Avče fault, Rasa fault) do not influence the general direction of the karst groundwater flow. The horizontal distance between Belo Brezno and the Mrzlek spring is 21 km, and the altitude difference is 970 m. The position of Uppertriassic and Jurassic beds, that dip towards Southwest enables the groundwater outflow from Belo Brezno to Hubelj. Uppertriassic dolomite is relative hydrogeologic barrier in the grounding of Jurassic limestone. By drawing the lifting of the flysch beds in the nearest hinterland of Hubelj at the Avče fault we try to show that interrupted and periodical appearance of the tracer in the Hubelj spring can be a consequence of the hydrogeological structure, too (Fig. 7.2). Cross-section 3 - 3' (Fig. 7.3) shows geologic and hydrogeologic conditions between the Vipava spring, injection points Malo Polje and Mrzli Log and the spring Divje Jezero near Idrija. At Malo Polje the dye was injected into the Jurassic limestone. Under the Uppertriassic dolomite of the Trnovo nappe and Čekovnik interjacent slice the dye flowed off towards Divje Jezero. The horizontal distance is 10,0 km and the altitude difference 295 m. Considering the geological conditions it can be expected that Malo Polje also belongs to the catchment area of the Hubelj spring although the tracing test did not confirm that supposition. Fig. 7.1: Geological cross-section 1-1'; Belo Brezno - Mrzlek. Fig. 7.2: Geological cross-section 2-2'; Belo Brezno - Hubelj. Fig. 7.3: Geological cross-sec-tion 3 - 3'; Vipava-Malo Polje-Mrzli Log-Divje Jezero. Fig. 7.4: Geological cross-section 4 - 4'; Rakitnik-Lokva-Vipava. Much more difficult is to explain the underground connection between Mrzli Log and Divje Jezero. The dye was injected in the sinkhole formed in the Uppertriassic dolomite of Trnovo nappe. As in the Čekovnik interjacent slice near Črni Vrh a hanging fissured aquifer is proved by a hydrogeological borehole it can be supposed that the dye gets lost through the shallow dolomite lid into the lower limestone of Koševnik interjacent slice, where a normal karstic flow towards Divje Jezero is possible. The horizontal distance between Mrzli Log and Divje Jezero is 7,2 km, while the altitude difference is 455 m. This geological cross-section (Fig. 7.4) explains the hinterland of the Vipava spring. P. Habič (1989) proved that the sinking stream Stržen near Rakitnik in the Postojna basin flows away in two directions, towards the Timava springs as towards the Vipava. The cross-section shows that the Lokva can have a normal underground karst flow towards the Vipava spring without any hydrogeological barrier. It has to be pointed that Lokva at low water can flow of into the limestone of Snežnik thrust sheet and trough it towards Timava. Although this geological cross-section is only supposed, it gives an explanation for the phenomenon, that the dye injected at low water in the Lokva stream did not appear in the Vipava spring. 7.2. UNDERGROUND WATER CONNECTIONS DEPENDENT ON HYDROMETEOROLOGICAL CONDITIONS (P. HABIČ) 7.2.1. The aim of water tracing by artificial tracers From 1993 to 1995 combined water tracing tests in the area of Trnovski Gozd and Nanos were achieved mostly at the same points but during various meteorological and hydrological conditions. Using mostly the same tracers provided that tracing results may be well compared one to another. Except in two cases, the tracers were poured into epikarst vadose zone, this is why their travel up to springs highly depended on rainfall, in particular on consecutive showers that washed the tracer from the injection area. The analyses of water and tracer pulses in such cases are specially interesting. The results of three consecutive water tracing tests in Belo Brezno below Golaki are important to understand water drainage in the area of Trnovski Gozd. Major part of tracer from the injection point at 1200 m a.s.l was flushed by rainwater into Mrzlek near the Soča (77 m a.s.l.), distant 19 km and partly into Lijak (water level between 77 and 116 m); smaller part flowed into near, 6,9 km distant Hubelj spring near Ajdovščina (water level between 220 to 270 m; See Chapter 6 about water tracing). Water tracing in immediate recharge SLEDENJE PODZEMNIH VODA NA TRNOVSKO-BANJSKI PLANOTI IN NANOSU, 1993 - 1997 UNDERGROUD WATER TRACING EXPERIMENTS ON TRNOVSKO-BANJSKA PUNOTA AND MT. NANOS, 1993 - 1997 zavod R Slovenije. LJubljano InWttut 20 TOztskovo krosa, Postojno Institut 20 9a