Olekma

a river in Chita and Amur oblasts and the Yakut ASSR, a right tributary of the Lena River. It measures 1,436 km long and drains an area of 210,000 sq km.

The Olekma originates in the Muroiskii Range of the Olekma Stanovik mountain system and flows in a broad intermontane valley toward the northeast. Turning northward, it flows between the Chel’baus Range on the east and the Southern and Northern Dyrynda and Kalar ranges. It then flows in a deep valley formed by the gap between the Udokan and Stanovoi ranges. Here there are rapids, and the current’s speed reaches 5–5.5 m per sec. Farther downstream, the deep valley of the Olekma separates the Chuga and Choruoda plateaus. The river then curves around the eastern side of the Olekma-Chara Plateau, the valley widens, and the current’s speed falls to 0.5–1.2 m per sec.

The Olekma is fed by rain and snow, with snow predominating downstream. In summer there are turbulent freshets. The mean flow rate is 1,950 cu m per sec. The river freezes in October, and the upper course in some years is frozen solid from February through March. The ice breaks up in May. The chief tributaries of the Olekma are the Tungir and Niukzha on the right and the Chara on the left. Freight is transported on the Tungir, which is linked by a highway with the Trans-Siberian Railroad; farther on, it is transported on the Olekma. The river is navigable by launch from its mouth to Eniuk. The city of Olekminsk is situated on the left bank of the Lena, near the mouth of the Olekma.