VELIKA VODA - REKA - A KARST RIVER VELIKA VODA-REKA - KRAŠKA REKA DANIEL ROJŠEK Izvleček UDK 551.444.3(450+497.4) Daniel Rojšek: Velika voda-Reka - kraška reka Veliko vodo-Reko najdemo v naravoslovni in drugi literaturi od antike naprej. Reka je klasični primer kraške reke na otoku neprepustnih kamenin sredi obsežnega kraškega sveta. O Reki imajo na Inštitutu za raziskovanje krasa ZRC SAZU v Postojni obdelanih kar 399 bibliografskih enot (V). Hidro-geografske značilnosti (2') Quvialno kraškega porečja Velike vode-Reke smo v tem prispevku povzeli po objavljenih študijah, rečni režim 40-letnega obdobja (1953-1992) (3') pa smo obdelali na novo. Ključne besede: rečni režim, fluvialno-kraško porečje. Seznam svetovne dediščine pri UNESCO, Velika voda-Reka, Timav, matični Kras, Slovenija, Italija Abstract UDC 551.444.3(4504-497.4) Daniel Rojšek: Velika Voda-Reka - a Karst River The Velika voda-Reka river is known in natural sciences and in literature since antiquity. The river is a classical representative of a karst river, isolated in a huge karst area. In the Postojna Karst Institute a rich bibliography containing 399 units exists (1'). Hydro-geographical features (2') of the Velika voda-Reka fluviokarst basin have been studied, published and summarized in this paper. The river regime for a period of 40 years (1953-1992) (3*) is presented for this paper. Key words: river regime, fluvio-karst drainage area, the World Heritage List by UNESCO, Velika voda-Reka, Timav - II Timavo, Karst, Slovenia, Italy Address - Naslov Mag. Daniel Rojšek, - MSc The Institute for Conservation of Natural and Cultural Heritage Delpinova 16 SI-5000 Nova Gorica Slovenia r Many thanks for the data to Mrs M. Kranjc from Inštitut za raziskovanje krasa ZRC SAZU at Postojna 2' Many thanks for the 1:400.000 map to Mr B. Rojc, PhD from Inštitut za geodezijo in fotogrametrijo FAGG in Ljubljana. 3'Many thanks for the data to Mr M. Kolbezen and Mrs D. Medvešček from Hidrometeorološki zavod Slovenije in Ljubljana. introduction The Velika Voda-Reka is a living name for the world famous karst river used by locals of the drainage area (Rojšek, 1992, 1993-2). Less adequate synonyms as the Notranjska Reka, Brkinska Reka, Timavo Superiore and similar can be found in the literature, too. The Velika voda-Reka is narrowly linked by the the Skocjan Cave System. The Reka is one of the most interesting natural features of the Skocjan World Heritage Site by U.N.E.S.C.O. (Rojšek, 1995). Sinking of the river into the Kras region, karst springs of Timav - II Timavo and Brojnice - Sorgenti di Aurisina - Nabrežina and hydro-geographical properties of the Reka have been admired and studied since antiquity. The Velika Voda-Reka is a classical representative of a karst river. The Reka drainage basin is caught between karst areas of the Snežnik massif, the upper Pivka fluvio-karstic drainage area, the Košansko-Slavinski ravnik karst plain and the Kras region (Fig. 1). karst river The karst river is a stream influenced by karst features. A surface karst river or its tributary can either spring out of a karst massif or the river sinks into it. The underground flow is either shallow or deep in the karst massif. The Velika Voda-Reka is the widest known sinking stream of the classical Kras. The drainage basin lies on the Brkini sinkline Eocene flysch rocks, that are isolated in a huge Mezozoic karst area. There are four karst tributaries to the Reka drainage network: the Bistrica, Podstenjšek, and Rakulšca Sušica-Mrzlek are the right ones, and the Završka Sušica is the left one (Fig. 1). About one cubic meter per second of the Reka water sinks into the Požiralnik Reke and in other swallow-holes near Gornje Vreme at the contact of Eocene flysch and Paleocene limestones at the beggining of the Vremska dolina blind valley (Rojšek, 1984). Sinking conditions at the contact change. The pothole that had opened on the 14th September, 1982 was flooded by high waters on the 2nd October, 1982. Cavers descended 22 m, 26 m and 20 m into the pothole for three times and found different levels of the cave. Its entrance was 9.4 m long and 5.5 m wide in August 1983 later it was widened (10.3 X 7.1 m in October 1985), but it was filled up with gravel few years ago. Fig. 1: The Velika voda-Reka drainage network and the Kras karst water junctions Soe*'^^ Vipava 0 2 4 6 8 10 km a>3a ^V^Slav^Ro- , Koäanski ^ K , ■ ravnik^ Snežnik KARST TRIBUTARIES: 1 Bistrica 2 Podstenjäek 3a Rakuläca - 3b Sužica 4 zavržka Sušica PONOR CAVES: a Markov spodmol b Požiralnik Reke C Škocjanska jama d Mejame KARST SPRINGS: A Brojnice - Sorgenti di Aurisina - Nabrežina B Timav - D Timavo ESTAVELLE E Gabranca WATER CAVES: K Kačja jama L Lobodnica -Grotta di Trebidano Scheme of the main channel network 3b Suäica-Mrzlek d=9.20 s S a, 2 Podstenjäek d=3.65 / 1 Bistrica d=1.65 •2 S e- r- IS 4 SuSica d=5.1I 5 Padež d=9^8 6 Posrtev d=9.28 d=5.11 - lenght of the main tributary channel in kilometres ^d - distance from the ponor in kilometres 7 Mola d=19.11 The main quantity of the water sinks into Škocjanska jama, the first cave of the Skocjan Cave System. Frequent floods make damages in the System's show part, and Šumeča jama is flooded up to the cave ceiling from Müllerjeva dvorana downwards. Waters of Senožeško Podolje, the Rasa, Branica, Vipava and Soča rivers, sink in the Kras aquifer, too. Brojnice - Sorgenti di Aurisina - Nabrežina and Timav - II Timavo springs represent direct outlets of the aquifer into the Adriatic Sea. The Brojnice submarine spring is the Reka's basic runoff outlet, but the Soča underground water prevails in Timav springs average discharge (Rojšek, 1987, 1993-3, Fig. 1). Basic hydro-geographic parameters of the basin: * the basin surface = 335 km^, * the mean sea level = 570 m, * the mean basin slope (without the Bistrica karst basin) = 26 %, * the permeability coefficient = 0.40, * the Velika voda-Reka length from the spring to - the swallow pothole Požiralnik Reke = 45.07 km, - the ponor Škocjanska jama = 51.60 km, - the syphon in Marchesettijevo jezero = 53.94 km. - the Mrtvo jezero underground lake = 54.02 km (Fig. 2), * the Velika Voda-Reka mean channel slope from the spring to - the swallow-hole Požiralnik Reke = 0.330 %, - the ponor in Škocjanska Jama = 0.332 % and - the syphon in Marchesettijevo Jezero = 0.676 % (Fig. 2). Some authors divided the basin into three parts: the upper, the middle and the lower one, but from hydro-geographical point of view there are three main hydro-geographical units: the Velika Voda-Reka fluvio-karstic drainage area, the classical Kras aquifer and marshy basin of the Timav springs (the Potok river - II Timavo) at the coast, where karst water drain into the Adriatic Sea. There are many drainage zones with different permeability in the Kras aquifer. The Reka underground course belongs to one zone of the aquifer, but the main affluent throughflow of the Timav belongs to the zone with underground water from the Soča drainage basin. The Kras aquifer surface of different limestones is estimated to 700 km^ where about 70 km^ belong to the Senožeško podolje and the Rasa fluvio-karst drainage area and about 20 km^ to other smaller areas. The aquifer permeability coefficient is estimated to 0.79 (Rojšek, 1981: 18). Data for the Velika Voda-Reka longitudinal profile were read in the 1:25.000 scale map and in works of Mihevc (1984-1, 2)*! and Rojšek (1981). Many thanks for the unpublished data to Mr A. Mihevc MSc from Inštitut za raziskovanje krasa ZRC SAZU in Postojna. S § g - S - a s _ sJ a : ä-B s P B 'S- i X o z u p s Ig K s 1 p s § H' to s ä to 8 i p 1 p © o o 1 S S -J s S i ti s 00 ^ ^ W K) I-. jiSpSpSSg'^ ^^ ^ to fJ g s s ts lis m pr-pppgopp ^aassssEE s 5' Ii' a I IS w r > to w w I Sä s g • f ^ vo ) 6 O^ s K S W w o ä is § iS III |Sf S š S g g O O 8 S p r- S S llgliiiis iiiisisii Si f TI crS" i to I Ki 5" 0 (Q 1 0 1 13 rt ^ 1 K S K Ei K _ as II §1 tSK^^SKKK-s »^ppopj^w^x ft B. «-f i 0 s 1 X/1 5* The Bistrica stream is the strongest karst tributary of the river. Water springs out of the Snežnik massif and the Koritniška Kotlinica small relief basin in the hinterland. There are some registered, but not explored and surveyed caves in the spring area, which is dammed for the reginal water supply. Basic hydro-geographical parameters are published (Rojšek, 1987: 14, 16). The Podstenjšek springs are located at the contact area of flysch and limestones. The highest water flows out of Kozja luknja, 85 m long and 20 m deep cave, where Proteus anguinus has been found. The Stržen-Sušica-Mrzlek channels network is the most developed among the right tributaries. The network of 45 channels with total lenght of 43.17 km is located in the area of 49.25 km^. Orographic watershed of this fluvio-karstic basin is uncertain and from the estavelle pothole Gabranca high waters of the Rakulšca stream from the other side of the Košansko-Slavinski ravnik flow off (Fig. 1). The Rakulšca karst water is accessible in the cave Vodna jama v Lozi between Markov spodmol and estavelle (F. Habe, F. Hribar, 1964). The Završka Sušica stream is the tributary without permanent flow consisting of 24.90 km long channel network of 11.04 km^ fluvio-karstic drainage basin. the velika voda-reka river regime Ilešič (1947: 101-102) was the first who was studied the Velika Voda-Reka river regime for the period 1898-1913. He determined the regime as pluvio-nival with poor nival influence related only to water level at the gauging station Ilirska Bistrica. Dukič (1968: 138-145) defined it as Mediteranean variant of the pluvial type regime with the highest average runoff in December and the lowest in August, but he used unrelevant data and his hydro-geographical study of the Reka is worthless. Rojšek (1981, 1983, 1984, 1987, 1990) studied and published the regime of the limnigraph gauging station Cerkvenikov mlin (25 and 30 years period 1953-77 and 1953-1982). According to data of 40 years period 1953-92 the last average regime was ascertained, illustrated with histogram and runoff regimes of the lowest and the highest waters (Figs. 3-6). Fig. 3: fflSTOGRAM OF THE MEAN RWOFF Velika voda-Reka gauging station Cerkvenikov mlin period 1953-1992 sQsCmV) JAN FEB MAft APR MAY lUN JUL AUG S > OCT NOV DEC Fig. 4: Velika voda-Reka runoff regime of the mean waters - Qs in m'^s ' gauging station Cerkvenikov mlin period 1953-1992 sQs" = 832 sQs(n)*= = L20 sQs(v)*' = 27.2 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC YEAR 15.9 6.66 2.20 4.76 5.85 6.95 6.98 1.01 2.73 732 9,09 3.2« 1953 6.47 4.84 10.7 3.49 12.4 4.78 2.24 0.50 133 3.16 936 12.7 1954 10.9 20.1 193 3.98 4.03 6.19 4.63 4.23 3.28 8.12 821 9.86 1955 10.9 11.6 3.98 15.1 11.2 6.98 2,31 0.64 0.48 4.09 143 2.00 1956 9.57 15.8 2.73 9.10 434 2.97 1.28 0.73 0.63 1.70 7.19 7.65 1957 13.9 14.7 11.8 9.01 1.% 2.88 136 0.69 0.62 3.13 8,45 23.8 1958 10.8 1.97 2.88 13.8 13.6 231 1.22 139 0.71 5,27 21.7 39.1 1959 13.7 26.8 20.8 4.10 121 L31 2.47 3.90 19,1 41.7 24,6 39.3 1%0 18.4 5.28 1.96 834 3.10 8.20 4.^2 1.93 0,47 10,7 23,6 11.0 1961 19.8 4.39 15.6 16.8 9.70 Z94 4,06 0.51 0,60 0.45 292 10.8 1962 20.1 9.26 14.2 8.0r7 5.25 7.88 1.16 4.11 7,18 12.4 21,8 835 1963 6.27 3.76 15.1 10.6 3.34 1.27 1.00 1.01 237 37,1 7,00 19.6 1964 20.2 5.72 13.6 6.66 10.6 16.0 3.46 1.76 35,4 4,57 16,8 243 1965 5.79 15.0 4.77 10.7 3.93 2.78 333 6,63 3,16 17,1 25,6 20.0 1966 8.20 11.8 8.76 19.2 8.47 4.94 1.02 0,62 1,06 1,05 8,33 492 1%7 7.11 32.6 5.76 2.90 6.94 4.96 132 4,05 5,96 Z17 22,8 9.88 1968 9.16 21.3 9.24 5.61 8.98 6.25 1.86 6.42 103 0,92 19,0 6.99 1%9 17.1 7.51 24.6 32.8 6.23 3.13 2.35 2.15 2,02 1,07 8,19 8.76 1970 15.7 12.5 15.3 12.4 4.93 7.13 1.16 0,58 033 0.49 5,23 434 1971 6.47 1L8 13.2 8.08 25.4 3.66 1S9 L15 2.66 1,74 16,6 122 1972 6.14 8.05 1.60 6.42 1.40 1.61 0.98 038 6,80 8,41 10,0 8.67 1973 726 10.6 6.17 5.42 113 IIJ Z80 0,91 334 25,4 7,70 4.35 1974 3.47 2.45 23.5 22.0 5.96 4.35 4J6 1,19 1,77 1,75 16,1 13.1 1975 1.20 14.1 6.90 9.50 2.93 1.96 0.83 1.77 9,91 820 193 31.0 1976 27.4 22.7 4.43 10.6 194 1.73 Z14 113 1.66 3,56 7,54 6.88 1977 17.7 14.5 12.0 15.5 1Z4 3.00 0.97 1.53 1,70 122 2,46 142 1978 28.2 28.2 20.9 18.4 4.61 1.06 0.60 0.58 5,54 634 20,6 11.1 1979 8.59 6.85 5.76 5.56 3.50 939 5.46 1,60 3,03 23,4 25,9 11.7 1980 3.29 Z73 a7 3.42 10.6 3.68 1.52 0,89 4,66 14,1 3.63 243 1981 1S.4 1.84 6.17 4.42 853 7.26 1.50 1.82 0,92 18.7 14.7 20.7 1982 3.80 3.42 12.6 lOJ 2.77 !.17 0.86 0.91 1.03 1.01 0.64 12.2 1983 9.21 11.2 7.29 12.1 6.74 6.10 2.49 L54 4,91 25.0 6.85 14.1 1984 16.4 8.11 17.4 14.6 10,4 4.01 2.03 1,21 1.23 0.75 3.20 3.42 1985 SS7 6.67 10.0 11.7 3.62 8.77 1.19 1.15 1.29 1.11 3.69 4.84 1986 4.44 24.6 4.11 6.61 10.2 3.45 2.47 2.29 3,19 9.46 26.6 10.1 1987 12.0 17.5 1Z3 123 4.69 9.25 1.19 1,76 231 5.43 0.91 3.49 1988 1.23 3.99 14.0 11,6 2.96 10.2 4.26 3.15 3,72 2.05 10.1 5.12 1989 4.18 3.44 2.11 10.7 1.99 5.51 1.52 1.75 234 11.1 223 18.1 1990 9.05 8.71 2.87 3.76 24.8 7.59 1.56 1,23 1.19 4.18 31.7 3.72 1991 1.84 4.27 1L2 11.5 337 232 Z98 1.33 1,49 28.6 183 242 1992 1.20 1.84 1.60 2.90 1.21 1.06 0.60 038 0,47 0.45 0.64 2.00 1.20 10.9 11.2 10.2 103 7.18 5.19 2.28 2.06 4.08 938 14.0 13.1 832 28.2 32.6 24.6 32.8 25.4 16.0 6.98 11.3 35,4 41.7 31.7 393 272 "the mean water of the period *®the lowest month mean water of the period •^the highest month mean water of the period Fig. 5: Velika voda-Reka runoff regime of the lowest waters - Qn(k) in mV gauging station Cerkvenikov mlin period 1953-1992 nQn(k)'' = 0.12 vQn(k)» ^ = 13.7 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC YEAR 2.37 1.98 128 1.28 119 1.28 038 0,30 0.12 0.44 0.79 034 1953 2.65 1.28 2.65 036 1:28 1.28 031 0,20 0.16 1.00 L75 2.49 1954 1.88 3.82 6.95 1.63 1.39 1.88 1,18 0,92 0.67 1.00 233 2.33 1955 3.00 3.40 1.27 3.20 2.60 2.60 0,80 0,36 0.29 0.36 3.62 1.05 1956 1.94 1.56 1.04 1.68 1.80 0.74 0.48 030 0.46 0.68 036 0.40 1957 2-22 3.22 6.32 338 0.80 0.62 0.68 0,37 0.43 030 1.12 1.12 1958 4.12 132 0.69 3.40 1.44 1.04 036 030 0.40 0.40 3.94 10.2 1959 250 4.40 632 1.68 0.74 036 0.96 120 1.04 12.2 5.84 9.04 1960 1.80 1.44 1.04 120 104 1.20 0.62 0,62 0.37 037 3.94 2.36 1961 4.83 2.52 2.85 334 1.93 130 0.80 0.28 0.28 0,19 033 2.52 1962 2.52 3.01 334 3.34 1.65 133 0.46 039 1.52 132 132 232 1963 2.95 1.20 2.62 3.97 1.41 0.86 033 033 0.48 0,78 1.65 189 1964 4.88 0.94 1.10 130 1.77 1.10 0.71 0.38 3.62 033 0,38 7.55 1965 2.84 4.11 2.84 3.25 2.47 194 1.87 2.00 194 3,25 8,76 4.47 1966 4.64 2.67 3.98 636 4.82 117 0.39 0,46 0.46 036 0,92 1.48 1967 250 230 2.85 1.70 2.04 156 1.03 1,03 1.27 1,07 1,17 1,96 1968 1.7) 337 3.22 275 2.60 2.25 131 103 168 0.60 032 3.16 1969 0.90 2.79 3.28 13.7 2.70 171 0.42 030 0.67 0.80 0,92 1.88 1970 2.70 2.70 1.71 3.18 236 1.62 0.86 0,22 0.32 0.22 0,22 1.19 1971 1.66 1.10 2.29 1.80 2.95 0.80 0.65 0,57 032 037 1,66 1,80 1972 1.15 2.08 1.25 1.25 0.57 0,39 0.48 0,30 030 1.35 135 1,35 1973 1.75 1.75 1.75 1.05 2.41 2.41 0.75 0,48 0.70 3.78 210 1,80 1974 1.66 1.10 2.16 Z55 1.74 1,42 1,26 0,97 0.90 0.84 103 2,94 1975 0.78 0.91 1.70 2.11 1.1« 0,68 0,49 0,63 111 0.97 211 200 1976 4.48 4.55 2.15 2.05 1.76 1,43 146 1,68 0.73 2.45 210 130 1977 2.20 5.49 5.29 Z80 4.10 0.80 0,68 0,52 0.64 0.80 0,56 1,30 1978 2.76 5.08 1.80 160 0.80 0.68 0,48 039 039 0.90 140 2,28 1979 2.30 2.00 1.90 2.30 1.90 2.30 1,80 130 1.30 120 5,05 2,90 1980 0.75 1.11 1.47 129 2.94 147 0.75 0,53 033 2.19 2,01 3,14 1981 2.37 1.35 1.07 1.69 135 1.52 035 0,64 0.28 0.37 2.55 3,07 1982 I.2I 2.20 2.72 1.69 1.21 035 0.46 0,46 0.28 0.28 0.19 035 1983 1.75 1.26 2.10 1.26 0.83 138 0.83 0,83 0.70 4.85 321 3,78 1984 2.48 2.48 3.07 6.84 1.39 1.39 0.91 0,91 0.60 030 0.91 1,52 1985 2.29 1.79 2.64 2.82 0.96 1.08 035 0.44 0.28 0.28 0.62 108 1986 2.02 2.98 2.02 2.59 2.39 2.02 0.63 031 0.31 2.02 3.18 338 1987 4.31 531 4.56 334 2.44 2.23 0.47 0.18 0.97 0.97 0.58 0,82 1988 0.50 0.87 Z04 2.64 0.87 1.67 1.67 0.87 1.33 1.33 149 167 1989 1.34 1.50 1.03 3.30 118 US 1.03 0.88 I.I8 1.68 2.65 5,26 1990 1.15 2.25 1.31 2.48 2.71 1.47 0.88 0.76 0.65 0.46 115 0,14 1991 1.32 1.57 132 2.45 1.40 1.25 1.40 0.74 111 til 3.03 2,45 1992 0.50 0.87 0.69 0.56 037 0.39 0,35 0.18 0.12 0.19 0.19 0,14 4.88 5.49 6.95 13.7 4,82 2.60 1,87 2.00 3.62 12.2 8.76 10,2 •'the lowest recorded peak of the lowest waters •^the highest recorded peak of the lowest waters Fig. 6: Velika voda-Reka runoff regime of the highest waters - Qv(k) in m^s ' gauging station CerJtveniifov mJin period 1953-1992 nQv(k)*' = 032 vQv(k)«='= 305 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC YEAR 192 74.9 4.24 29.9 18.0 19.6 363 7.00 17.6 65.S 96,0 18,0 1953 25.4 24.2 364 28.6 633 203 10.4 0.61 28.2 13.4 129 543 1954 102 68.2 167 14.4 16.7 40.8 274 314 30.2 68.2 27,8 47,1 1955 63.7 49.9 12.8 81.2 48.6 25.4 17.0 L16 3.40 56.7 92,6 12.2 1956 54.0 76.7 7.36 42.9 233 24.9 11.2 1.94 1.04 125 66,7 443 1957 115 136 40.0 39.4 4,88 29.7 4.40 3.58 132 412 57,3 203 1958 465 4.12 14.9 65.7 107 13.8 4.40 7.08 2.50 103 115 174 1959 69.7 147 128 11.2 1.80 15.6 6.56 215 182 235 85,1 186 1960 198 66.2 6.08 553 170 58.7 93.6 135 0.74 142 145 5.20 1961 88.9 14.9 84i 62.1 67.6 12.4 47.8 0.80 3.88 1.08 109 62.6 1962 166 94.8 65.6 166 33.7 83.3 6.80 36.7 34.9 169 183 33.9 1963 31.1 26.6 81.5 44.5 9.56 5.65 2.62 5.45 307 248 30,7 109 1964 87.8 26.2 105 52.6 111 110 19.8 68.7 277 255 85,1 185 1965 36.6 49.8 12.2 49.8 24.0 18.9 14.2 612 263 93.0 195 204 1966 3Z2 149 17.4 . 119 63.7 54.7 Z93 0.85 3.57 4.82 87,8 29.8 1967 48.7 147 183 263 96.0 56.1 4.69 61.7 59.6 8.61 231 276 1968 «5 15T 28.» 17.7 m J9.4 3.5J 31.6 77.7 155 240 19.6 1969 109 16.8 174 123 19.0 12.4 9.15 42.2 143 356 72,7 131 1970 86.7 151 162 134 11.3 44.0 3.05 0.86 1.08 7.00 48,7 23.0 1971 77.4 61.5 126 19.1 305 23.4 25.6 631 14.2 16.6 101 68.8 1972 113 633 2.61 23.1 7.49 3.71 0.83 0.32 0.32 11.1 813 61.1 1973 39.3 116 94.8 651 58.6 97.2 2U 3.10 34,2 172 41,9 13.6 1974 44.6 8.57 204 91.8 57.7 610 43.2 21.6 13,6 13.9 262 116 1975 2.11 174 231 39.4 10.9 8.00 lil 263 151 188 77,7 178 1976 98.4 115 14.9 94.8 23.6 2.80 223 118 9.61 14.4 65,1 96.6 1977 224 56.2 36.2 93.0 63.5 22.1 2.44 50.0 111 104 54.7 94.2 1978 lOl 69.9 85.2 138 223 3.82 1.00 1.40 93.6 105 214 96.6 1979 101 48.2 26.7 46.4 15.7 67.8 23.9 253 73.2 119 119 84.0 1980 10.4 13.1 52.8 29.8 106 18.6 4.31 7.52 39.7 912 9,65 159 1981 104 2.72 65.1 21.0 753 65.6 5.20 12.0 290 97.2 157 73.2 1982 13.2 7.13 102 60.5 9.84 2.90 2.03 1.69 4.80 10.4 5,41 121 1983 94.0 81.4 62.1 112 47.7 23.6 16.8 4.15 45.2 233 53,7 150 1984 113 543 lis 40.8 44.2 17.1 433 5.67 1.82 1.82 16,1 22.9 1985 56.1 54.6 49.2 79.8 301 833 6.95 8.39 9.35 5.09 614 345 1986 15.0 124 3Z4 21.7 36.6 18.1 9.78 27.2 66.9 76.7 235 27.9 1987 53.9 77.5 101 68.9 18.0 75.7 456 12.8 38.1 68.9 2,44 16.0 1988 330 643 106 56.0 8.86 67.5 225 372 33.9 9.16 162 20.1 1989 16.0 772 7.72 47.0 6.33 30.9 6.33 10.7 8.86 73.1 168 229 1990 52.3 110 5.71 6.83 160 66.2 3.80 3.27 20.8 315 243 15.0 1991 4.01 20.S 117 593 23.0 12.0 23.8 3,42 8.54 175 844 259 1992 2.11 2.72 2.61 6.83 1.80 2.80 0.83 0.32 0.32 1,08 1,44 5.20 102 115 105 79.8 63.7 61.0 2Z5 314 39.7 105 162 159 104 116 106 81.2 67.6 65.6 23.8 36,7 45.2 119 168 174 109 124 117 91.8 753 66.2 23.9 37.2 59.6 142 183 178 113 136 118 93.0 96.0 67.5 25.6 37.6 66.9 169 195 185 115 147 126 94.8 106 67.8 27-4 42.2 732 172 214 186 US 147 128 112 107 75.7 363 50.0 77.7 175 231 203 166 149 162 119 111 833 43.2 61.2 93.6 188 235 204 192 151 167 123 160 833 433 61.7 151 233 240 229 198 157 174 134 198 972 47.8 68.7 182 235 243 259 224 174 204 138 305 110 93.6 118 277 248 262 276 *^the lowest recorded peak of the highest waters *^the highest recorded peak of the highest waters The Velika Voda-Reka river regime of the 40 years period is determined as Submediteranean pluvio-nival with influence of karst retention. The average water level related to the period is 8.32 m-''s"'. The highest mean water occurs in November, and the lowest in August. The highest mean monthly discharge belongs to the late autumn, winter and spring (Nov., Dec., Jan., Feb., Mar., Apr.). From November the average discharge decreases to January, it fluctuates from February to April and decreases again from May to August, to increase in November (Figs. 3, 4). Total subaverage discharge (20.79 m's ') does not reach one and the half of the highest average monthly discharge. The runoff regime of the lowest waters shows that the lowest monthly peak of the period does not exceed one cubic meter per second, but one hundred and twenty liters per second (0.12 m^s ') is the lowest recorded discharge. The highest monthly peaks of the lowest waters range from 1.87 to 13.7 m's'^ (Fig. 5). Oscillating flood waves are characteristics of the highest runoff regime. The highest discharges have been not measured. The Cerkvenikov mlin gauging station discharge curve is uncertain in the upper part, thus the highest discharges displayed in the Fig. 6 are too low. The highest peak was recorded in September 1965 with discharge 277 m's', but in the Fig. 6 the highest discharge of 305 m's ' (May 1972) is shown. Hidrometeorološki zavod Slovenije - the Slovene hydrological institute processed the data of both flood waves (Rojšek, 1987: 19). The wave computation showed lower peak discharges. By the curve 222 m's ' was computed as the 1972 wave's peak, but afterwards by the runoff and precipitation comparative analysis the peak of 305 m-^s ' was estimated. The analysis of the 1965 wave has not yet been done. In six months of the period (Jan., Feb., Mar., Oct., Nov. and Dec.) the highest peaks at least ten times expand beyond 100 m-^'s '. The peak more than 100 m-'s"' appeared every month of the period, except in July (93.6 m-^s '). In seven months of the period (Jan., Mar., May, Sep., Oct., Nov. and Dec.) 200 m's"' appeared in November six times even (Fig. 6). A ratio between the lowest and the highest discharge is unknown, but it is more than 1:3.000. degradation The Velika Voda-Reka river was also known by overpollution of its waters from the Ilirska Bistrica town downwards. The river was degraded to sewer and the Cave System to sewage outlet of the town and regional agricultural, communal and industrial waste waters. The basic river pollution parameters were published by Rojšek (1987, 21, 1990). From that time quality of the water improved, particulary after the independance of Slovenia in 1991. After that time the last big pollutant the Tovarna organskih kislin (Factory of organic acids ) collapsed; Yugoslav army left barracks, and they are abandoned as military objects, however some pollutants still exist. Building of projected communal water treatment plant for town, which should be built up in the year 1991 did not even started; also the validity of the plan location permission expired. The location procedure must start again, because inhabitants of Topole village opposed to the plant location. The main reason of their discontent was the presumable plant stinking. The water is no more overpolluted, but it is still in the 2nd to 3rd class, according to discharge. Diluting of communal waste water by fresh outlets from two accumulations in the Mola drainage basin is not appropriate and sufficient method to maintain the Velika Voda-Reka quality in the 2nd class. The functional communal cleaning plant is the only right way and a guarantee to maintain the river quality in the 2nd class. conclusion A karst river is a stream influenced by karst features. A surface karst river or its tributaries either flow out of a karst massif or sink into it. The underground flows are shallow or deep in the karst massif. The Velika Voda-Reka is a classical representative of a karst river. Its drainage basin lies mostly on the Brkini sinkline of the Eocen flysch rocks, which is isolated in a huge Mezozoic karst area. The Reka is narrowly linked by the Škocjan Cave System, the World Heritage Site. The river frequently floods the cave system (Figs. 1 and 2). The Reka has a Submediteranean pluvio-nival river regime with influence of karst retention. The average water level for the period 1953-1992 is 8.32 m-'s"'. The highest average water appears in November, the lowest in August. The runoff regime of the lowest waters shows that the lowest monthly peak of the period does not exceed one cubic meter per second, but one hundred and twenty liters per second (0.12 m-''s ') is the lowest recorded discharge. Oscillating flood waves are characteristics of the highest runoff regime. The highest discharges were not measured. The Cerkvenikov mlin gauging station discharge curve is uncertain in the upper part, thus the highest discharges in the figure 6 are too low. The highest discharge of the period was estimated to 305 m-^s"', however the peak was higher (Figs. 3-6). A ratio between the lowest and the highest discharge is unknown, but it exceeds 1:3.000. The water is no more overpolluted, but it is still in the 2nd to 3rd class, according to discharge. The water treatment plant of the Ilirska Bistrica town and industry is the only appropriate way to guarantee that the river quality remains in the 2nd class. references Dukič, D., 1968: Režim reka u krasu Jugoslavije.- Cvijičev zbornik SANU, 138-145, Beograd. Habe, F. & F. Hribar, 1964: Sajevško polje.- Geografski vestnik. Vol.: 36, 13-49, Ljubljana. Habe, F. 1982: Notranjska Reka izginila v breznu.- Proteus, Vol.: 45, No.: 3, 96-99, Ljubljana. Mihevc, A. 1984-1: Nova spoznanja o Kačni jami - New discoveries in the Kačna jama cave.- Naše jame. Vol.: 26, 11-20, Ljubljana. Mihevc, A. 1984-2: Kačna jama.- 9. Jugoslavenski speleološki kongres, 417-422, Zagreb. Ilešič, S. 1947: Rečni režimi v Jugoslaviji.- Geografski vestnik, Vol: 19, 71-108, Ljubljana. Kranjc, A. & A., Mihevc 1988: Poplavni svet ob Notranjski Reki - Flood Area Along the Notranjska Reka River.- Geografski zbornik. Vol.: 28, 193-218, Ljubljana. Rojšek, D. 1981: Hidrogeografske značilnosti in degradacija porečja Reke.-Diplomska naloga. Knjižnica Oddelka za geografijo Filozofske fakultete v Ljubljani. Rojšek, D. 1983: Hidrogeografske značilnosti in degradacija porečja Notranjske Reke ter Škocjanske jame.- Mednarodni simpozij "Zaščita Krasa ob 160-letnici turističnega razvoja Škocjanskih jam", 52-56, Sežana. Rojšek, D. 1984: Vodne razmere v porečju Reke in v Škocjanskih jamah leta 1983.- Naše jame, Vol.: 26, 69-71, Ljubljana. Rojšek, D. 1987: Fizičnogeografske značilnosti in naravne znamenitosti porečja Notranjske Reke - Physico-geographical Characteristics and Natural Features of the Notranjska Reka R. Drainage Basin.- Varstvo narave, No.: 13, 5-24, Ljubljana. Rojšek, D. 1990: Human Impact on Škocjanske jame System.- Studia casologica, No.: 2, 120-132, Brno. Rojšek, D. 1992: O nekaj imenih s Krasa in Posočja - About some geographical names from the Kras and the Posočje,- Geografski vestnik, Vol.: 64, 185-190, Ljubljana. Rojšek, D. 1993-1: O imenih jam - About Cave Names.- Naše jame. Vol.: 35, No.: 2, 114-116, Ljubljana. Rojšek, D. 1993-2: Nekaj imen s Krasa - Some geographical names from the Kras.- Naše jame. Vol.: 35, No.: 2, 116-120, Ljubljana. Rojšek, D. 1993-3: Škocjanski jamski splet - The Škocjan Cave System.- Naše jame. Vol.: 35, No.: 2, 120-123, Ljubljana. Rojšek, D. 1995: Inventory of the Škoqan World Heritage Site,- Acta carsologica. Vol.: 24, 477-485, Ljubljana. velika voda-reka - kraška reka Povzetek Med domačini v porečju je Velika voda-Reka živo ime za svetovno znano kraško reko (D. Rojšek, 1992, 1993-2). V literaturi najdemo bolj ali manj neustrezne sinonime: Notranjska Reka, Brkinska Reka, Timavo Superiore in podobno, reka Reka pa je zagotovo med najbolj nesmiselnimi. Ponikanje Reke v matični Kras, kraška izvira Timav in Brojnice pod Nabrežino ter druge hidro-geografske značilnosti Reke so občudovali in preučevali od antike dalje, kajti Velika voda je klasični primer kraške reke. Kraško reko bistveno zaznamujejo vplivi krasa. Površinska kraška reka oziroma njen pritok lahko izvira iz krasa ali pa reka vanj ponika, podzemeljska se skozenj pretaka bolj ali manj globoko. Porečje Velike vode se razteza na eocenskih Hišnih kameninah brkinske sinklinale, ki tvori otok neprepustnih kamenin v obsežnem, večinoma mezozojskem kraškem svetu Snežniškega pogorja, Košansko-Slavinskega ravnika in matičnega Krasa ter fluvialno-kraškega porečja zgornje Pivke. Velika voda je del Škocjanskega jamskega spleta, kjer ima svoje mesto med zagotovo najbolj zanimivimi naravnimi pojavi v naravni in kulturni dediščini, ki je vpisana v Seznam svetovne dediščine pri UNESCO. Poplave v jamskem spletu so pogoste. Najvišje poplavne vode zalijejo Šumečo jamo do stropa od Miillerjeve dvorane navzdol. Reka ima štiri kraške pritoke: Bistrica, Podstenjšek in Sušica-Stržen-Mrzlek so desni, završka Sušica pa levi (sliki 1 in 2). Reka ima pri Cerkvenikovem mlinu submediteranski pluvio-nivalni rečni režim z vplivi kraške retinence. Srednja voda obdobja 1953-1992 znaša 8.32 Najvišji poprečni odtok je novembra, najnižji pa avgusta (sliki 3 in 4). V odtočnem režimu najnižjih voda vidimo, da najnižja konica nikdar ne preseže kubičnega metra v sekundi, stodvajset litrov v sekundi (0.12 ra-''s"') pa je najnižji opaženi pretok (slika 5). Temeljna značilnost odtočnega režima najvišjih voda je nihanje višine silovitih poplavnih valov. Najvišjih pretokov niso nikdar izmerili, temveč so jih izračunali. Pretočna krivulja vodomerske postaje Cerkvenikov mlin v zgornjem delu ni zanesljiva, tako da so konice iz sHke 6 prenizke. Obdobna konica iz 305 mV (maj 1972) je ocenjena, najvišja se je pojavila septembra 1965, vendar je nihče še ni na novo ovrednotil. Razmerje med najnižjim in najvišjim pretokom ni znano, presega pa 1:3.000. Voda Reke ni več tako onesnažena kot pred leti, vendar njena kakovost še vedno niha med 2. in 3. razredom, kar je večinoma odvisno od pretoka. Razredčevanje odplak v Reki s svežo vodo iz zadrževalnikov Klivnik in Mola ni pravi niti zadovoljivi način čiščenja Reke. Učinkovita komunalna čistilna naprava bi bila edino, kar bi nedvomno jamčilo da Reka ostane v drugem kakovostnem razredu.