Lake Cerknica is intermittent lake appearing at the bottom of closed depression Cerkniško polje extending on the area of 38 km2. The karst features are associated with carbonate rock, both with limestone and dolomite. About 80 % of inflow consists of karst and only 15% of surface waters. The outflow is completely karstic. In spring and usually late in autumn the lake reaches normal level 550 m a.s.l., covering the area of 26 km2. Polje is flooded for 9 and dry for about 2 months, usually in summer. Lake Cerknica is a highly diverse ecosystem that changes in time and space. Vegetation pattern shows clear zonal distribution that depends on extent and frequency of flooding. The lake supports rich fauna with many endangered species, providing temporary shelters and food for protected large carnivores, such as brown bear, wolf, lynx and numerous species of water birds. In recent decades, flood and drought events have become increasingly irregular altering processes and conditions for many species.