a river in Penza, Saratov, Voronezh, and Volgograd oblasts, RSFSR; a left tributary of the Don River. The Khoper River is 979 km long and drains an area of 61,100 sq km. It rises on the Volga Upland and flows through hilly terrain. It is fed primarily by snow. High water is in April and May. The mean flow rate 45 km from the mouth is 150 cu m per sec (maximum, 2,720 cu m per sec). The river freezes in November or December (in some years, in the first half of January); the ice breaks up in late March or April. The principal tributaries are the Serdoba and Buzuluk on the left and the Vorona and Savala on the right. The Khoper River is used as a water supply source. It is navigable from Novokhopersk (323 km). The cities of Balashov, Novokhopersk, and Uriupinsk are situated on the river; the Khoper Preserve is in the valley of the river’s lower course.