The Římov reservoir was constructed in 1971–1978 at 21.85 km of the Malše River (tributary of the Vltava River), downstream its confluence with the Černá stream. The reservoir serves as an important drinking water supply for South Bohemia and helps to maintain a minimum flow downstream. The dam is 47 m high and 290 m long. Reservoir volume is 34.3×106 m3, the catchment area is 489 km2.Mean annual flow is 4,3 m3 s-1 and mean theoretical water retention time 92 days. The Římov reservoir is a canyon-shaped impoundment with steep banks, the „tower“ for drinking water input is at 5 m distance from the dam. Being a drinking water source, Římov Reservoir is protected and no other uses are allowed.
Regular investigations of the Římov reservoir in its lacustrine part started in 1979 and have continued at three-week intrevals up to now. Since 1996, the Římov reservoir has been a part of the Czech LTER network. The parameters studied include physical, chemical and biological data on pelagic organisms like bacteria, protists, phytoplankton and zooplankton. Once per year, the abundance and species composition of fish is investigated. Besides regular monitoring, a lot of extensive studies were done of pelagic organisms, their diversity, interactions and functions as well as chemical processes in water and sediment, both in the lacustrine part and in the canyon-shaped riverine part near the inflow. Such intense studies were possible due to the vicinity of well equipped labs in České Budějovice and the construction of a field station at the dam (in 1994).