formed in 1956–59 by the dam of the Irkutsk Hydroelectric Power Plant on the Angara River, in Irkutsk Oblast, RSFSR. It is actually the flooded valley of the Angara River between the dam and the source of the river from Lake Baikal; it has numerous narrow inlets.
The reservoir has an area of 154 sq km, a length of 65 km, and a width ranging from 4 km at the dam to 0.5 km at Lake Baikal. As a result of the backwater created by the Irkutsk Hydroelectric Power Plant, the average level of Lake Baikal has risen approximately 1 m over the years. The reservoir’s effective volume totals 46.5 billion cu m. The Irkutsk Reservoir is used for the long-term regulation of the water’s flow. The city of Irkutsk is located on the reservoir. There are houses of rest, camps for pioneers, and sports facilities on its shores.