Hutovo blato was declared as park of nature in 1995. Because its outstanding beauty and significance. Karst water from hills makes larger number of lakes, gorges and river Krupa and ensures a high level of groundwater, coming down hill in valleys. High level of underground water effects on appearance of constant and semi-constant springs and wells. Lakes of Hutovo blato represents crypto depressions, because the bottoms of some lakes are under the sea level ( Jelim 18m ). The biggest lakes on Hutovo blato are: Deransko, Jelim, Drijen, Orah, Škrka and Svitava. Svitava lake is artificial accumulation, made during the construction of hydropower Čapljina. All lakes of Hutovo blato are mutually conected with large number of canals and gorges.