engleski

Contribution to understanding some hydrogeological relationships in Dinaric Karst

Beside lithostratigraphic and tectonic conditions, hydrogeological conditions are dominant factor in speleogenesis of all caves in Dinaric Karst. Remarkable examples of hydrogeological complexity of this area have been found in some caves. More precisely occurrences of bifurcation and high difference between groundwater levels. Many groundwater flows located in the vicinity of local river watersheds have been discovered in the Inner Karst area (Kordun). The depth of karstification in this area is estimated to be between 200 and 450 m and the deepest vertical caves explored are about - 150 m deep. „Jama pod Debelom glavom“ cave is the perfect example of this occurrence. One underground water flow of the cave belongs to Korana river catchment and the other, located just a few meters away, belongs to Glina river catchment. In the Outer Karst area, where the depth of karstification is estimated to be between 1500 and 2500 m „Jama kod Pavlinovica“ provides an information about water level fluctuation with minimum difference of 236 m. During the hydrogeological survey in 1976 speleologists have descent the cave several times to the depth of - 234 m. No active groundwater flow was found. A few months later, during the rainy season, the water was pouring out from the cave and created a lake with a depth about 2 meters. The cave still hasn't been completely explored. The main reason being the owners on the land who use the cave as a sewage drain for their household located just a dozen meters from the cave. In the Middle Karst area, where the depth of karstification is estimated to be between 500 and 1200 m examples of sudden demarcations between Adriatic and Black Sea watersheds were discovered. During the construction of highway A6 (Rijeka – Zagreb) near Lokve in tunnel „Sleme“ several deep caverns belonging to Adriatic watershed were discovered. Just a few meters away in the caverns in front of north-east tunnel entrance a Black Sea watershed was discovered. These examples show complexity of geological relationships caused by impermeable beds within the karstified limestones. Tectonics caused sudden changes of permeability which caused the changes in underground water flows.

Speleology, Karst Hydrogeology, Dinaric karst, Croatia

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