Case Studies from the Dinaric Karst of Slovenia

The other problem of karst is water, especiallyalong Adriatic coast where the highestlack of water occurs during summer. Thisis a result of low amount or precipitation andhigh evapotranspiration. For the water supply,some aqueducts were made in antiquity (Bonacci1987). More common are wells, whichwere often built in closed depresions (Fig. 35).Fig. 36: During Austro-Hungarian Empire and Yugoslaviakingdom surface streams were regulated, ponors were widenedand screens were installed in front of them to holdback deposits, all in order to shorten the flood time in karstpoljes. Example from Šica ponor at Radensko polje (Račnapolje; Slovenia; photo: M. Prelovšek).A greater impact was made by the irrigationof some poljes to avoid long lasting floods.They enlarged ponors on poljes and even dugsome tunnels for the floodwaters. None theless, enlargement of ponors successfully reducedthe length of floods only at places,where a restristions were close to the ponors.At places with regional rise of water level, enlargementof ponors brought only minor success.However, the main impact on the karst wasmade by the use of waters in power stations.Especially high mountainous karst has beenvery interesting from the hydroenergeticsaspect due to a high amount of precipitation,high runoff coefficient (about 0.7), high reliefamplitude and relief suitability. Especiallyduring the 1950s and 1960s, big hydroenergeticprojects were initiated on Dinaric karst poljesin Croatia, Bosnia and Herzegovina. Largeworks were done in the Trebišnjica river karstby flooding part of the karst (Fig. 37 and 38),by diverting water to other catchment areas(Fig. 39) and stopping regular flooding of thePopovo polje (Milanovič 2006). Importanthydroenergetic objects were placed also inCetina, Lika-Gacka and Zeta river basins. Inthe present day situation, hydroelectric powerplants in the Dinaric karst have a total installpower of over 2,727 MW. Nevertheless, thelevel of environmental concern about someareas (e.g., Planinsko polje, Cerkniško polje,Pivka basin, Reka valley, and the Kupa/KolpaRiver) was so high that these areas remainhydroenergetically untouched.Fig. 37: Hutovo accumulation lake at the downstream end of Popovo polje (on the right), Herzegovina (photo: M. Prelovšek).47