a river in Irkutsk Oblast and Krasnoiarsk Krai, RSFSR; right tributary of the Enisei. It is 2,989 km long and drains an area of 473,000 sq km. The Nizhniaia Tunguska River rises in the southern part of the Middle Siberian Uplands, east of the Angara Ridge. In its upper course (down to the mouth of the Ilimpeia River), it flows through a broad valley; its bed has many shoals. In its lower course, for a distance of 1,300 km, there are numerous lake-like widenings (up to 20–25 km). In crossing the traps, the river flows through gorges (less than 200 m wide) with precipitous sides (100 to 200 m high), forming rapids and long rocky shoals 8–10 m high. Downstream from the rapids are whirlpools and depths of 60–100 m. The river’s average depth is 4 to 6 m; at the shoals, depths range from 2.5 to 3.0 m. The largest rapids are the Zhdanovskii, Vivinskii, Uchaminskii, and Bol’shoi. At the rapids the river flows at a rate of 5 m/sec.
The Nizhniaia Tunguska is fed primarily by snow. High water occurs in the upper course in May and June and in the lower course from May through July. The mean flow rate at the mouth is 3,680 cu m per sec; the maximum flow rate is 74,000 cu m per sec 125 km from the mouth. In the winter the water level lowers significantly, with runoff amounting to less than 1 percent of the annual total. The river freezes in October or early November and thaws in May. The sheet ice moves from four to 11 days, during which time huge ice jams form in the narrows of the river and the water level rises by 20–35 m.
The principal right tributaries of the Nizhniaia Tunguska are the Kochechum, Vivi, Tutonchana, and Severnaia; the principal left tributaries are the Nepa, Bol’shaia Erema, Ilimpeia, Taimura, and Uchami. During high water, the river is navigable from the settlement of Tura (center of the Evenki National Okrug); there are boat and barge routes in the upper course. The harbor of Turukhansk is located at the river’s mouth. The Tunguska Coal Field is in the Nizhniaia Tunguska basin.
K. G. TIKHOTSKII