The region is located in the drainage basin of Vltava river. Other significant rivers are Malše, Lužnice, Otava, Nežárka and Lomnice. South Bohemia is known for its many ponds. In the past, more than seven thousand ponds were established across the region. With its 489 ha Rožmberk is the largest one, followed by Bezdrev (450 ha) and Horusice pond (415 ha). In the 20th century, a series of dams was constructed on Vltava river. Lipno Dam is the largest dam in the Czech Republic and has area of 4,870ha. Other dams in the region are Orlík Dam, Římov Dam and Hněvkovice Dam.