a river in the Mongolian People’s Republic (MPR) and China. Length, 1,264 km (1,090 km in the MPR); basin area, 116,400 sq km.

The Kerulen has its sources on the southeastern slopes of the Henteyn Mountains; in its upper reaches it flows through a narrow wooded mountain valley, sometimes in canyons. In its middle and lower course it flows through a broad, terraced valley. The river bed has a great many islands, oxbow lakes, and swampy sections. The Kerulen empties into Lake Hulun (Dalai Nor). Its upper terraces are occupied by arid steppe; its lower terraces, by meadows and tugai (bottomland with forest and scrub). The river’s water capacity decreases along its course because of evaporation and the diversion of the water for irrigation. The high-water period occurs during the summer, and every year there are several flash floods caused by rains. The river is icebound from November through April, and in many places it freezes over completely. The river is abundant in fish (taimen, carp, and catfish). The city of Choibalsan (MPR) is located on the Kerulen.