a reservoir formed in 1957–58 by the dam of the Iriklinskii Hydroengineering Complex on the Ural River in Orenburg Oblast, RSFSR. The reservoir covers an area of 260 sq km, has a volume of 3.3 cu km, measures 70 km long and 8 km across its widest part, and has a maximum depth of 34 m and an average depth of 12.7 m. It forms a large embay-ment in the Suunduk River.
The purpose of the reservoir, whose level fluctuates within a range of 11 m, is the long-term regulation of water flow. The reservoir was created as a water supply source for industrial enterprises and municipal services of the cities of Orsk, Novotroitsk, and other centers of population. It is also used for flood control in the vicinity of Orsk, for irrigation, and for power and water transport purposes.