Severnaia Sosva

a river in Tiumen’ Oblast, RSFSR; a left tributary of the Malaia Ob’, which is a branch of the Ob’ River. The Severnaia Sos’va measures 759 km long and drains an area of 98,300 sq km. It is formed by the confluence of the Bol’shaia Sos’va and Malaia Sos’va rivers, which originate on the eastern slopes of the Northern Urals. It flows over the northwestern section of the Western Siberian Lowland in a wide marshy valley; its vast floodplain reaches 40 km in width. At its widest point, the river measures 1 km. The lower Severnaia Sos’va flows through the Ob’ River valley, parallel to the Ob’ River. Numerous streams connect the Severnaia Sos’va, the Malaia Ob’, and the Vogulka, a tributary of the Severnaia Sos’va, as a result of which numerous islands have been formed. The largest tributaries are the Liapin, on the left, and the Malaia Sos’va, on the right.

The Severnaia Sos’va is fed predominantly by snow. High water is from May through September. The average flow rate is 860 cu m per sec. The river freezes in late October or early November, and the ice breaks up in late April or May. Timber is floated on the Severnaia Sos’va. The river is navigable in the lower course, where there are also gas deposits.