tributary of the Yenisey River in western Siberia, Irkutsk oblast (province), Russia. It has a total length of 1,159 miles (1,865 km) and a drainage basin of 96,100 square miles (249,000 square km). Known in its upper section as the Katanga, it rises on the Central Siberian Plateau near the watershed with the Lena-Angara system and flows generally northwestward to join the Yenisey at Podkamennaya Tunguska village. Its upper part has a wide, swampy valley; its lower section has numerous falls and rapids. The river is navigable for 710 miles (1,140 km) to the village of Vanavara.