a reservoir formed by the dam of the Ust’-Ilimsk Hydroelectric Power Plant on the Angara River. Filling began in 1974. Area, 1,873 sq km; volume, 59.4 cu km. Length along the Angara, 300 km; along the Him, 299 km. Maximum width, 12 km; average depth, 32 m; maximum depth, 91 m. The level of the reservoir fluctuates up to 1.5 m, regulating seasonal changes in discharge. The reservoir was built for energy production, water transportation, and the floating of timber.