Podkamennaia Tunguska

(also called Chulakan and Sredniaia Tunguska), a river in Krasnoiarsk Krai and Irkutsk Oblast, RSFSR, a right tributary of the Enisei. The Podkamen-naia Tunguska measures 1,865 km long and drains an area of 240,000 sq km. It rises in the Angara Ridge. The upper course, known as the Katanga, flows through a broad and deep valley. At the mouth of the Tetere River, the valley narrows and the Podkamennaia Tunguska enters a zone of trap development. There are numerous rapids—Nizhnii, Oron, Chambinskii, Pano-likskii, Miriuginskii, Dedushka, and Vil’minskie—and the speed of the current here is 3–4 m/sec. At a distance of 250 km from the mouth, the valley widens to 20–23 km, and there are many bars in the channel.

The Podkamennaia Tunguska is fed predominantly by snow (60 percent); rain accounts for 16 percent, and groundwater for 24 percent. The high water period is from early May to late June; in the lower course it lasts until early July. The low water period is from July to October, with periodic flash floods (one to four per season), which raise the water level by as much as 5.5 m. The mean flow rate at the mouth is 1,750 cu m per sec; the greatest flow rate is 35,000 cu m per sec, and the least, which occurs in the winter, 3–15 eu m per sec. Ice begins forming in mid-October. The autumn ice drift lasts seven to 16 days, and ice dams develop. By late October, the river is completely frozen. The ice breaks up in mid-May, at which time there is ice drift of five to seven days in the upper course and up to 10 days in the lower course. The ice drift is very rapid. The resulting ice dams cause the river’s water level to rise to 29.7 m.

The tributaries are the Tetere and Chunia on the right and the Kamo and Vel’mo on the left. The Podkamennaia Tunguska is navigable for 1,146 km. During the high water period, large vessels travel as far as Baikit (571 km); river launches with barges are used above that. Vanavara, Baikit, and Podkamennaia Tunguska are the principal population centers on the river.