Lena (the Yakut. Ulahan-Jurah - the big river), the river in Eastern Siberia, one of the greatest rivers of Russia and globe. Length of 4400 km, the area of pool of 490 thousand km2. Proceeds on Irkutsk area and Yakut ÀÑÑÐ. Originates (under the name the Big Lena) from small lake on the western slope of Baikal mountains, at height of 930 m. Runs into Laptev sea. The most part of pool of Lena is located in the field of universal distribution of frozen rocks and covered with a taiga.
Lena is navigable from Kacug up to a mouth; up to Ust-Kut it is accessible only to courts with small îñàäêîé. Navigation proceeds about 160 day in to top of current and about 120 day in a lower reaches. The main quayes: Bulun, Zigansk, Yakutsk, Olyeklimsk, Lenek, Vitim, Kirensk, Osetrovo (Ust Kut), Zigalovo, Kacug. From inflows are navigable: Kirenga, Vilyui, Vitim, Olyekma, Aldan...
The rivers of pool of Lena possess rich stocks of hydraulic power. On ðíêå Vilyui - Vilyui HYDROELECTRIC POWER STATION, on the river Mamakan - Mamakan HYDROELECTRIC POWER STATION. The pool of Lena is rich with minerals. In system of the river Vitim it is located Bodajbo, and in system of the river Aldan - Aldan gold-bearing areas; in a river basin Vilyui - deposits of diamonds. There are also deposits of coal (Lenski and the Southern-Yakut pools), natural gas, iron ore, mica, stone salt, etc. Industrial fishery is advanced in a lower reaches of Lena.
The first data on Lena are received Russian in the beginning of 17 centuries; in 1631 it is based Óñòü-Êóòñêîå çèìîâüå, in 1632 - the Yakut jail. Scientific researches of Lena and its inflows have been started by participants of 2-nd Kamchatka expedition (1733-43). In 20th years of 19 centuries they were carried out by expedition under the direction of P.F.Anzhu, in 1873-1875 - A.L.Chekanovskogo, in 1885-1886 - E.V.Tollja, etc.