A storage reservoir (777 ha) on the Samica river, connected by the Wonieæ channel to the Obra river. The reservoir comprises five former lakes (Drzeczkowskie, Witos³awskie, Wojnowskie, Jezierzyckie, Wonieæ), connected by a narrow channel (c.13 km long, 200-1,300 m wide), with meadows between them. A dam and sluice divide the upper part of the reservoir, where aquatic vegetation is well-developed, from the lower, where such vegetation is very localized. Adjacent there are fish-ponds, forests, meadows and cultivated fields. The reservoir stores water for agriculture and fire-fighting.
The globally threatened Aythya nyroca has not bred here since 1995, but the habitat remains and it is believed there is a good chance that it could breed here again, therefore criterion B2 is still applied. Breeding species of global conservation concern that do not meet IBA criteria: Haliaeetus albicilla (one pair). Other notable breeding species include Anas strepera (22 pairs) and Chlidonias niger (20-60 pairs).
Pressure/threats to key biodiversity
Birds are disturbed by fisheries, hunting, tourism and angling, and are also threatened by rapid changes in water-level.
National High International None900 ha of IBA covered by Protected Landscape Area (Krzywiñsko-Osiecki, 71,425 ha).