Designing a national groundwater quantity monitoring network on groundwater bodies with alluvial aquifers in Slovenia
Načrtovanje državne mreže za spremljanje količin podzemne vode na vodnih telesih podzemne vode z aluvialnimi vodonosniki
Petra Souvent1, Zlatko Mikulič 1, Mišo Andjelov1, Vlado Savič 1
1 Environmental Agency of the Republic of Slovenia, Vojkova cesta lb, SI-1000 Ljubljana, Slovenia; E-mail: petra.souvent@gov.si, zlatko.mikulic@gov.si, miso.anjelov@gov.si, vlado.savic@gov.si
Received: July 31, 2007	Accepted: October 4, 2007
Abstract: Five out of 21 groundwater bodies (GWBs), which have been delineated in Slovenia with regard to the EU Water Framework Directive (WFD), comprehend mostly alluvial high permeability aquifers. They cover approximately 10 % of the country area but contribute to about 50 % of all groundwater abstraction and to about 40 % of all drinking water to the Slovenian water supply system. The existing groundwater quantity monitoring network (GWQMN) mostly covers the areas within the GWBs which are of drinking water pumping interest. To meet all the requirements of WFD and to enable reliable assessments of the quantity status of GWBs, the existing old network has been redesigned with the help of GIS tools with the great emphasis on hydrogeological, geological and pedological characteristic of GWB. Described method of network design leads to 36 new monitoring sites on GWBs with alluvial aquifers. Redesigned national GWQMN provides better coverage of spatial differences within GWBs and shall provide data needed to better understand the groundwater regime in the GWBs.
Izvleček: Za potrebe ocenjevanja stanja podzemnih voda in njihovega upravljanja je bilo v Sloveniji določenih 21 vodnih teles podzemne vode v skladu z Vodno direktivo. Pet vodnih teles podzemne vode, s pretežno visoko prepustnimi aluvialnimi vodonosniki, se razprostira na približno 10 % Slovenije, vendar se iz njih črpa okoli 50 % podzemne vode, oziroma 40 % vse pitne vode. Obstoječa državna mreža za spremljanje količin podzemne vode je do sedaj dobro pokrivala le področja, ki so pomembna z vidika vo-dooskrbe. Glede na nove prostorske enote ocenjevanja stanja voda je bilo potrebno državno mrežo za spremljanje količin podzemnih vod izpopolniti in zadovoljiti zahtevam metodologije ocenjevanja količinskega stanja.
Uporabili smo prostorsko analitično metodologijo v GIS tehnologiji, ki je upoštevala hidrogeološko, geološko in pedološko homogenost danega ozemlja ter pri analiziranju prostora upoštevali različne tipe in režime varovanja. Z opisano metodo smo določili 36 novih merilnih mest na vodnih telesih s pretežno aluvialnimi vodonosniki. Izpopolnjena državna mreža za spremljanje količin podzemne vode nudi boljšo pokritost prostorsko in hidrološko različnih območij znotraj vodnega telesa in zagotavlja boljše razumevanje režima podzemne vode v danem vodnem telesu.
Key words: groundwater, groundwater monitoring, groundwater monitoring network design, groundwater quantity, alluvial aquifer
Ključne besede: podzemna voda, monitoring podzemne vode, načrtovanje mreže, količina podzemne vode, aluvialni vodonosnik
Introduction
Underthe EUWaterFrameworkDirective[1], a total of 21 groundwater bodies[2] have been delineated in Slovenia, with mostly karst and fissured porosity aquifers (68.9 %), followed by aquifers with intergranular porosity (26.2 %) and special case of aquifers in napped tectonic structures and aquitards (4.9 %). Five GWBs (Figure 1) with mostly alluvial, high permeability aquifers are of special interest in this study as they contribute about a half of Slovenian abstracted groundwater, but their area cover just approximately 10 % of the country. In the year 2005, about 467x106 m3 of groundwater was available and 116.4*106 m3 abstracted from these GWBs.
The first groundwater quantity monitoring network (GWQMN) in Slovenia was
established in the year 1952 when observers started GW level measurements in 20 private wells. This was the beginning of the national monitoring in the alluvial aquifers. The number of monitoring sites has changed with the time with regard to the Slovenian water policy. The maximum was reached in the year 1960 with 244 monitoring sites (Figure 2). In the year 2007 the national GWQMN has 128 monitoring sites in the alluvial aquifers within 5 GWBs.
So far, the existing groundwater quantity monitoring network mostly covered the areas within the GWBs which are of drinking water supply interest. To meet all the needs of WFD and to enable reliable assessments of the quantity status of GWBs, the existing network has been redesigned using GIS tools[3].
Figure 1. GWBs with mostly alluvial high permeability aquifers
Slika 1. Vodna telesa podzemne vode (VTPodV) s pretežno aluvialnimi
vodonosniki
Figure 2. Development of the national groundwater quantity monitoring network in Slovenia
Slika 2. Razvoj državne mreže za spremljanje količin podzemne vode
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Designing the groundwater quantity
monitoring network
The leading idea was to divide the area of GWBs into logical units according to the hydrogeological, geological and pedologi-cal characteristics (Figure 3) and afterwards to add areas protected by law. These protected areas include Natura 2000 sites established under the EU Habitats Directive (92/43/EEC)[4] and the EU Birds Directive (79/409/EEC)[5] as well as Drinking Water Protected Areas established under Article 7[6] of the WFD.
Hydrogeological spatial data layer comprises all known hydrogeologically distinct units within specific GWB and distinguish between different hydrological regimes, such as: areas with direct infiltration of rainfall into alluvial aquifer were separated
from the areas fed by the runoff from the hills, as well as recharge from rivers and inflow from other aquifer systems. Perched aquifers were defined and delineated too. They overlay the lover hydrogeological unit. On Figure 4, an example of hydro-geologically distinct units is presented for the GWB Mura valley.
For each GWB pertaining catchment area was determined. Catchment area was divided in sub-catchment areas that represent catchments for each logically separated spatial unit. On Figure 5, as best and clear example among alluvial GWBs, a catchment area and its sub-catchment areas are presented for the GWB Savinja valley. In the case of trans-boundary GWB, the areas of groundwater inflow from another country and groundwater outflow from Slovenia were separated too.
Figure 3. Concept of joining spatial data layers (SDL) into one logical subsystem of GWB
Slika 3. Koncept združitve prostorskih podatkovnih slojev (PPS) v homogeni podsistem vodnega telesa
Figure 4. Hydrogeologically distinct units within GWB Mura valley Slika 4. Hidrogeološko različna območja znotraj mej VTPodV Murska kotlina
Figure 5. Catchment area and sub-catchments areas for the GWB Savinja valley
Slika 5. Zaledje in podenota zaledja prikazana za primer VTPodV Savinjska kotlina
The geological spatial data layer was constructed with the help of geological maps[7] (1:100000) and lithological cross sections, if available. In this layer, each GWB was divided into geological units according to the surface geology (Figure 6). Lithological cross sections were used for better understanding of the sub-surface geology.
Pedological spatial data layer consists of areas defined due to soil characteristic (Figure 7). The source of information in this process were the general digital pedo-logical map of Slovenia[8] with soil types, map of mean soil depth[8] and map of mean textural soil classes in Slovenia[8].
All three spatial data layers were combined into one composite layer (Figure 3) with GWB units, representing areas with a similar hydrogeological regime, geology and pedology (Figure 8). Such an analysis of GWBs has enabled selection of new monitoring sites by the principle: each logically separated spatial GWB unit should have at least one groundwater monitoring site. Within these units, protected areas were also separated, represented by one monitoring site as a rule. In the areas with no hydrological data of groundwater monitoring, the area of the groundwater body was divided due to aquifer systems defined by Geological Survey of Slovenia[9], and the density of network was adjusted accordingly.
Figure 6. Geological units within GWB Mura valley Slika 6. Geološke enote znotraj mej VTPodV Murska kotlina
Figure 7. Soil Characteristics within GWB Mura valley Slika 7. Tipi tal znotraj mej VTPodV Murska kotlina
Figure 8. Spatial data layer with the GWB units (13) indicating the similar hy-drological regime, geology and pedology (example for GWB Mura valley) Slika 8. Prostorski podatkovni sloj z območji (13), kjer je podoben hidrološki režim, geologija in pedologija (primer za VTpodV Murska kotlina)
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Table 1. Main alluvial GWBs (Figure 1) with existing and new monitoring sites Tabela 1. VTPodV s pretežno aluvialnimi vodonosniki (slika 1) z obstoječimi in novimi merilnimi mesti
	The Sava valley & Ljubljana moor	The Mura valley	The Drava valley	The Savinja valley	The Krško valley
Area in km2	774	591	429	109	97
Number of areas with the similar hydrological regime, geology and pedology (GWB units)	28	13	12	7	6
Number of existing monitoring sites (GW monitoring program 2007)	41	24	18	19	26
Number of new monitoring sites	28	1	3	2	2
Total number of monitoring sites	69	25	21	21	28
Results and discussion
Checking the existing GWQMN with the help of described method has shown that majority of the existing monitoring sites within relevant GWB fits well into this new concept of network design. Anyhow, redesign of existing national GWQMN still led to certain number of new monitoring sites (Table 1) which will be added to the GWQMN. On Figure 9, for example, the existing and planned monitoring sites
are presented for the GWB Sava valley and Ljubljana moor.
Following the design study phase in the office, field inspection has begun and is still in progress, with the purpose to confirm or to reject the chosen new locations. The GWQMN will be completed with the new monitoring sites gradually, till the year 2013, within the project: "Upgrading of hydro-meteorological system for monitoring and analysis of waters in Slovenia" [10].
Conclusions
Described method of network design has enabled easier selection of monitoring sites and has facilitated the set up of better GWQMN. Redesigned national GWQMN shall provide better data needed to under-
stand groundwater regime in the GWBs, enable reliable assessments of the quantitative status of a GWB, shall facilitate the national groundwater quality monitoring network redesign and offer additional data for a modeling of groundwater flow in the alluvial aquifers.
Figure 9. Existing (41) and planned (28) monitoring sites for the GWB Sava valley and Ljubljana moor
Slika 9. Obstoječa (41) in planirana (28) merilna mesta na VTPodV Savska kotlina in Ljubljansko barje
Povzetki
Načrtovanje državne mreže za spremljanje količin podzemne vode na vodnih telesih podzemne vode z aluvialnimi vodonosniki
Državna mreža za spremljanje količin podzemne vode na vodnih telesih podzemne vode s pretežno aluvialnimi vodonosniki (slika 1), vključuje večinoma obstoječe objekte, kot so: piezometri, vrtani vodnjaki in kopani vaški vodnjaki, ki prvotno niso bili namenjeni za spremljanje globine do podzemne vode v sklopu državne mreže. Državna mreža je bila v preteklosti usmerjena predvsem na območja, ki so bila pomembna za vodooskrbo. S sprejetjem Evropske vodne direktive - VD (EU Water Framework Directive (WFD)) in z definiranjem 21 vodnih teles podzemne vode na območju Slovenije, se je koncept za spremljanje količin podzemne vode prilagodil VD. Da bi zadostili potrebam VD, mora Slovenija spremljati in oceniti količinski status vodnih teles v skladu z zahtevami VD in z mrežo optimalno pokriti celotno vodno telo podzemne vode. Tako smo z novim pristopom načrtovanja državne mreže za spremljanje količin podzemne vode na vodnih telesih s pretežno aluvialnimi vodonosniki preverili, kako dobra je pokritost vodnih teles z dosedanjo mrežo in v primeru nezadostne pokritosti optimalno pokrili območja znotraj vodnih teles z novimi merilnimi mesti. Pri tem smo uporabili prostorsko analitično metodologijo v GIS tehnologiji, ki je upoštevala hidrogeološko, geološko in pedološko homogenost danega ozemlja ter pri analizi-
ranju prostora upoštevali različne tipe in režime varovanja.
Vodilna ideja metodologije je bila razdeliti območja vodnih teles na logične enote glede na hidrogeološke, geološke in pedološke karakteristike danega ozemlja. Tako smo za vsako vodno telo s pretežno aluvialnimi vodonosniki (za 5 teles - slika 1) kreirali tri prostorske podatkovne sloje, ki smo jih potem združili v skupen prostorski podatkovni sloj:
•	Hidrogeološki prostorski podatkovni sloj,
•	Geološki prostorski podatkovni sloj,
•	Pedološki prostorski podatkovni sloj.
Hidrogeološki prostorski podatkovni sloj Hidrogeološki prostorski podatkovni sloj vključuje vsa znana hidrogeološko različna območja znotraj danega vodnega telesa in tako razlikuje med različnimi hidrološkimi režimi. Izdvojena so bila tudi območja z visečo podtalnico. Območja s prevladujočo direktno infiltracijo padavin v aluvialni vodonosnik smo tako ločili od območij, ki se večinoma napajajo iz zaledja. Izdvojili smo območja, kjer reka napaja vodono-snik in območja, kjer je dotok podzemne vode iz drugih vodonosnih sistemov. Slika 4 prikazuje hidrogeološke enote znotraj VTPodV Murska kotlina. Za vsako vodno telo smo definirali odgovarjajoče zaledje, ki je razdeljeno na več pod-zaledij. Vsako pod-zaledje odgovarja enemu izdvojenemu območju znotraj vodnega telesa. Na sliki 5 je primer zaledja in pod-enote zaledja prikazan za VTPodV Savinjska kotlina. Ločili smo tudi cone dotoka podzemne vode iz sosednjih držav ter cone iztoka podzemne vode iz Slovenije.
Geološki prostorski podatkovni sloj Geološki prostorski podatkovni sloj je nastal na podlagi osnovne Geološke karte, znanih litoloških presekov vodnih teles in litologije pridobljene iz vrtin iz baz Geo-ZS in Oddelka za hidrologijo podzemnih voda. V tem podatkovnem sloju je vodno telo razdeljeno na območja glede na geologijo na površju vodnega telesa. Litološke preseke smo uporabili za boljše razumevanje geologije pod površjem. Na sliki 6 so prikazane geološke enote znotraj mej VT-PodV Murska kotlina.
Pedološki prostorski podatkovni sloj Pedološki prostorski podatkovni sloj je sestavljen iz območij, ki smo jih določili glede na karakteristike tal določenega vodnega telesa. Podatke o tipih tal smo pridobili iz osnovne pedološke karte Slovenije, karte o povprečni globini tal v Sloveniji ter karte o povprečnem teksturnem razredu tal v Sloveniji. Na sliki 7 so prikazani tipi tal znotraj mej VTPodV Murska kotlina.
Združitev vseh treh prostorskih podatkovnih slojev
Vsi trije podatkovni sloji so bili združeni v en prostorski sloj, ki predstavlja območja s podobnim hidrogeološkim režimom, geologijo in pedologijo. Združen prostorski podatkovni sloj je prikazan za primer VTPodV Murska kotlina na sliki 8.
Takšen pristop k izpopolnitvi mreže nam je omogočil preveritev obstoječe mreže in izbor novih merilnih mest oz. lokacij
po načelu: vsaka logično izdvojena enota na vodnem telesu mora biti pokrita z vsaj enim merilnim mestom. Na območjih, na katerih ne razpolagamo s hidrogeološkimi podatki, so bila območja znotraj vodnega telesa izdvojena na podlagi vodonosnih sistemov, ki jih je določil GeoZS, temu primerno je bila prilagojena gostota mreže.
Preveritev državne mreže za spremljanje količin podzemne vode na vodnih telesih z opisano metodo je pokazala, da se večina obstoječih merilnih mest znotraj danega vodnega telesa dobro vklaplja v opisani koncept izpopolnitve mreže. Opisana metoda je pripeljala do 36 novih lokacij na petih vodnih telesih s pretežno aluvialnimi vodonosniki. Po končanem kabinetnem delu smo začeli s terenskimi ogledi novih lokacij z namenom, da potrdimo ali ovrže-mo le-te.
Opisana metoda omogoča lažjo izbiro novih lokacij oz. merilnih mest in olajšuje postavitev optimalne državne mreže za spremljanje količin podzemne vode na vodnih telesih s pretežno aluvialnimi vodo-nosniki. Takšna mreža nam bo zagotavljala bolj kakovostne podatke za poznavanje hidroloških režimov na danih vodnih telesih in bo omogočala zanesljivo oceno količinskega stanja vodnih teles. Olajšala bo izpopolnitev državne mreže za spremljanje kvalitete podzemne vode in zagotovila dodatne podatke, ki jih potrebujemo za modeliranje toka podzemne vode v aluvialnih vodonosnikih.
References
[1]
[2]
[3]
[4]
[5]
[6]
Directive 2000/60/EC of the European Parliament and of the Council (WFD).
Official Journal of the European Communities. 2000, 72 p.
URL RS 63/05 (2005): Pravilnik o določitvi vodnih teles podzemnih voda (Rules on determining water bodies of groundwater).
Souvent, P., Gale, U., Mikulič, Z., And-jelov, M., Trišič, K, Savič, V. (2007): Strokovna izhodišča za izpopolnitev merilne mreže za spremljanje količin podzemne vode. Interno gradivo Sektorja za hidrologijo, (Hydrogeological Guidelines for Upgrading Groundwa-ter Quantity Monitoring Network), 104 str.
Council Directive 92/43/EEC of 21 May 1992 on the conservation of natural habitats and of wild fauna and flora.
Council Directive 79/409/EEC of 2 April 1979 on the conservation of wild birds.
Article 7 of the WFD (2000): Waters used for the abstraction of drinking water. Official Journal of the European Communities. p. 12.
[7]
[8]
[9]
[10]
Geological map of Slovenia (23 separate sheets) in GIS environment (2003). Geological survey of Slovenia.
Soil data of Slovenia (2007), Centre for Soil and Environmental Sciences of Biotechnical Faculty. Dostopno na svetovnem spletu http://www.bf.uni-lj.si/cpvo/Novo/main_PodatkiTalSlo-venije.htm.
Geološki zavod Slovenije (2004): Nacionalna baza hidrogeoloških podatkov za opredelitev teles podzemne vode Republike Slovenije. Sklepno poročilo 3. faze. (Geological Survey of Slovenia (2004): National base of hydrogeological data for groundwater body determination in Slovenia).
Agencija RS za okolje (2006): Projekt: Nadgradnja sistema za spremljanje in analiziranje stanja vodnega okolja v Sloveniji (SSSV). (Environmental Agency of the Republic of Slovenia (2006): Project: Upgrading of hydro-meteorological system for monitoring and analysis of waters in Slovenia).