a storage lake in the southwestern Karelian ASSR. Ianis”iarvi has an area of 200 sq km, an average depth of 12 m, and a maximum depth of 57 m. It is fed by snow and rain. The water level varies by 2.6 m; when the lake is regulated, it varies by 2.8 m. The highest levels are in early June, and the lowest in April. The lake freezes over in November or the first half of December, and the ice breaks up in late April or May. A hydroelectric power plant is located at the place where the Ianisioki flows out of the lake.