The Plitvice Lakes National Park, founded in 1949, is located in the central part of the Dinaric karst region in Croatia. Large karst springs and 16 lakes separated by tufa barriers and waterfalls are the fundamental natural phenomenon of the national park, which has a million visitors a year. Lakes are recharged by water from the mountainous region of Lika, and the runoff is directed towards the Black Sea catchment. The whole area of the National park is composed of carbonate rocks with different levels of natural permeability and very complex tectonic relationships, which allowed discharge of groundwater, maintaining the lake and fi nally partial loss of water to the karst underground after passing through the lake system. Prošćansko and Kozjak are the two largest lakes which dominate and by their internal dynamics ensure maintenance of the high water quality of the whole system. A conceptual hydrogeological model of the Plitvice Lakes was the result of complex research in the framework of international cooperation between the University of Zagreb and the Joanneum Research Institute in Graz. The research identifi ed completely new data about the genesis of the water system, the hydrogeological characteristics of the karst water catchment, the dynamics of the water in the lakes, locations of water loss from the Plitvice Lakes system, the "hanging" position of Lake Kozjak in relation to groundwater and a whole range of other data important for the preservation and protection of water resources in the National Park. Throughout the project were made 3022 measurements of different physicochemical parameters, 7885 of the chemical analysis of water and 1082 analysis of stable isotopes.

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IzvlečekUDK 556.3(497.56) Ranko Biondić, Hrvoje Meaški & Božidar Biondić: Hidrogeologija ponornega območja reke Korane dolvodno od Plitviških jezer, HrvaškaDolvodno od Nacionalnega parka Plitviška jezera vode, ki tečejo skozi sistem jezer, oblikujejo reko Korano. Nekaj sto metrov pod to izvirno cono v času poletnih sušnih obdobij voda v strugi ponika in s časom povsem presahne. Ponorno cono gradijo zelo dobro prepustne karbonatne kamnine in šele po prehodu na manj prepustne dolomite približno 17 km nižje po strugi Korana postane stalna reka. V članku so obravnavane hidrogeološke razmere v coni ponikanja vode v strugi in odnosi s sosednjim porečjem reke Une, pa tudi možnosti prestavitve vira oskrbe s pitno vodo iz jezera Kozjak (Plitviška jezera) na novo lokacijo v ponorni coni reke Korane. V ta namen so bile izvedene hidrogeološke raziskave, izvrtanih je bilo več piezometrskih vrtin in izvedena sta bila dva sledilna poskusa za določitev smeri podzemnega toka v času nizkih vod. Rezultati so pokazali, da je v sušnih obdobjih v ponorni coni reke Korane nivo podzemne vode z aktivnim vodonosnikom približno 25 m pod strugo. To odpira možnost dodatnih raziskav za rešitev problema oskrbe z vodo in prestavitve zajetja vode na tem območju. Oba sledilna poskusa sta dokazala povezavo z izvirom Klokot (Bosna in Hercegovina) v sosednjem porečju reke Une, kar kaže na čezmejni značaj vodonosnika. Minimalni pretok izvira Klokot je približno 3 m 3 /s, maksimalni pa več kot 75 m 3 /s. Zajetje za oskrbo z vodo v ponorni coni reke Korane z izdatnostjo približno 60 l/s ne bo imelo vpliva na pretok izvira Klokot. Ključne besede: Dinarski kras, ponorna cona reke Korane, Plitviška jezera, sledilni poskus, čezmejni vodonosnik, zajetje podzemne vode. AbstractUDC 556.3(497.56) Ranko Biondić, Hrvoje Meaški & Božidar Biondić: Hydrogeology of the sinking zone of the Korana River downstream of the Plitvice Lakes, CroatiaDownstream of the Plitvice Lakes National Park, water that pass through the water system of the lakes begins its flow as the Korana River. A few hundred meters downstream of the source zone, during the summer dry periods, there are losses of water in the riverbed resulting in its total drying. The sinking zone in that area is built of high permeable carbonate rocks and with the appearance of less permeable dolomite rocks, about 17 km downstream, the Korana River becomes a permanent river. This paper focuses on the explanation of hydrogeological relations in the zone where losses of water occur in the riverbed, relationship to the neighbouring Una River catchment, as well as possibilities of relocating the source of water supply from the Kozjak Lake (Plitvice Lakes) to the new site in the sinking zone of the Korana River. For this purpose hydrogeological researches were performed, with drilling of several piezometric boreholes and two tracing tests to determine the direction of groundwater flow during the dry season. The results show that during the dry periods in the sinking zone of the Korana River the groundwater level with ac...

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