a lake in Vologda Oblast, RSFSR, in the Severnaia Dvina basin. In 1917 it was converted into a reservoir. It has an area of 648 sq km, with the lake proper totaling 407 sq km. Its average depth is about 3 m.
Stretching from northwest to southeast, the lake lies in a swampy lowland at an elevation of 109 m. It is about 60 km long and up to 15 km wide. The lake’s banks are shoaly and its bottom mostly sandy. It is fed by mixed sources, chiefly by snow. The lake’s level may vary by as much as 1.5 m, with the highest levels occurring from May through July and August. There is a great deal of turbulence.
The lake freezes in October or November and thaws at the end of April or in May. It is part of the Volga-Severnaia Dvina Waterway system (built in 1828 and rebuilt in 1917). At the point where the Sukhona River flows out of the lake there is a dam for seasonal regulation of flow and a navigation lock. The Porozovitsa River, which flows into the lake, and the Severnaia Dvina Canal connect the lake with the Sheksna River of the Volga basin. White salmon, bream, pike, and pike perch are caught in the lake.