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(also, in Yakut, Ulakhan-Iuriakh, “big river”), a river in Eastern Siberia; one of the largest rivers in the USSR and the entire world. Length, 4,400 km. Basin area, 2,490,000 sq km. It flows through Irkutsk Oblast and the Yakut ASSR. Rising (under the name of Bol’shaia Lena) from a small lake on the western slope of the Baikal Range at an elevation of 930 m, the Lena empties into the Laptev Sea. The major part of the Lena basin is situated in a region of perennially frozen rock and soil and is covered by taiga, with the exception of a small area north of 71°N lat., which is situated in tundra and forest-tundra.
The upper reaches of the Lena and a considerable part of the basins of its right tributaries flow through mountain areas including the Baikal and Transbaikal regions and the Aldan Plateau. The main part of the left-bank basin of the Lena is located in the Central Siberian Plateau. The lowest section of the Lena basin lies along its middle (Central Yakut Lowland) and lower course.
The river is divided into three main sections: the upper (from its source to its confluence with the Vitim), the middle (from the mouth of the Vitim River to the confluence of the Lena with the Aldan), and the lower (from its confluence with the Aldan to its mouth). In its upper course the Lena passes through a deep-cut valley, whose rocky and steep slopes frequently tower over the river by as much as 300 m. The width of the valley ranges from 1–2 to 10 km, narrowing at certain points to 200 m. Pianyi Byk (“Drunken Bull”), the most famous narrow point in the river, is located 237 km downstream of the city of Kirensk. Here, the Kirenga, a large right tributary, flows into the Lena.
Along its middle course the Lena becomes a deepwater river, but it especially increases in size after it receives the Olekma. The width of the channel reaches 2 km, and the valley, 30 km. At this point there is an extensive floodplain with numerous small lakes. Below the mouth of the Olekma (up to Pokrovsk) the river valley is narrow with precipitous, deeply dissected limestone slopes, which form separate cliffs that are frequently of unusual shapes (the “Lena Columns”). Large tributaries flow into the Lena along its middle course: the Vitim, Bol’shoi Patom, Olekma with the Chara, and the Aldan from the right and the Niuia from the left.
Below the mouth of the Aldan River the Lena enters the region of the Central Yakut Lowland. Its valley again widens to 20–25 km, and the width of the floodplain is 7–15 km. The floodplain contains many lakes and swamps. The river channel branches, and navigability varies. Depths reach 16–20 m. In the lowermost reaches, near the village of Bulun, where the river passes between the Kharaulakh Mountains and the Chekanovskii Ridge, the valley narrows to 2 km. In this section the Lena receives the Viliui, a large left tributary.
Before flowing into the Laptev Sea, the Lena forms a vast delta (with an area of approximately 30,000 sq km), which is divided by numerous branches (up to 150). The largest channels of the delta are the Trofimov (discharging up to 70 percent of the river’s water into the sea), Bykov, and Olenek. The Bykov channel (106 km long), which connects the Lena with Tiksi Bay, is the most important one for navigation.
The Lena is fed mainly by melted snow (50 percent of annual flow) and rain. Groundwater accounts for 1–2 percent. The regimen of the river is characterized by high floodwater (along the middle course water levels rise by 10–15 m and along the lower course by 18 m), summer rain freshets, and little flow in the winter. In terms of water volume the Lena occupies second place (after the Enisei) among the rivers of the USSR. Average annual discharge at the mouth is approximately 17,000 cu m per sec (with a maximum of 200,000 cu m per sec and a minimum of 366 cu m per sec). Above the mouth of the Kirenga River the average annual discharge is 480 cu m per sec; at the mouth of the Vitim, 1,700 cu m per sec; at the mouth of the Olekma, 4,500 cu m per sec; at the mouth of the Aldan, 6,800 cu m per sec; and at the mouth of the Viliui, 12,100 cu m per sec. Average annual flow into the Laptev Sea totals approximately 540 cu km. Each year the Lena discharges into the sea about 12 million tons of suspended sediment and 41 million tons of dissolved substances. Water turbidity does not exceed 50–60 g per cu m. Mineralization of water varies from 80–100 mg per liter during high-water periods and freshets to 160–500 mg per liter during lowwater periods. The highest water temperature is 19°C in the upper course and about 14°C in the lower course (July). The Lena is free of ice for five or six months in the south and four or five months in the north. The river usually becomes icebound ten days after the tributaries. In the upper course the Lena becomes icebound in late October and in the lower course, sometimes in late September. The ice breaks up as late as mid-May in the upper course and by early June in the lower. Ice jams occur during spring ice flow, sharply raising water levels. Ice layers are characteristic of the rivers of the Lena basin.
The Lena is navigable from Kachug to the mouth. Up to Ust’-Kut it may be traveled only by ships with small draft. The river is navigable for about 160 days in the upper course and 120 days in the lower. The major landings are Bulun, Zhigansk, Yakutsk, Olekminsk, Lensk, Vitim, Kirensk, Osetrovo (Ust’-Kut), Zhigalovo, and Kachug. Navigable tributaries include the Kirenga, Viliui, Vitim, Olekma, and Aldan. In the summer regular tourist cruises are organized on the Lena.
The rivers of the Lena basin have rich reserves of hydroelectric energy. The Viliui Hydroelectric Power Plant has been constructed on the Viliui River, and the Mamakan Hydroelectric Power Plant operates on the Mamakan River. The Lena basin has abundant supplies of minerals. The Bodaibo and Aldan goldbearing regions are found in the Vitim and Aldan river systems, respectively. The basin of the Viliui River contains diamond deposits. There are also deposits of coal (Lena and South Yakut basins), natural gas, iron ore, mica, and rock salt. Commercial fishing is well developed on the lower course of the Lena, where the main part of the catch consists of muksun, Siberian cisco, nelma, Arctic cisco, taimen, and burbot. Lenok, grayling, dace, pike, and perch are caught on the upper course.
Information about the Lena was first obtained by Russians in the early 17th century. The Ust’-Kut winter station was founded in 1631 and the Yakut fortress in 1632. Scientific investigations of the Lena and its tributaries were first conducted by participants of the Second Kamchatka Expedition (1733–43). In the 1820’s investigations were conducted by an expedition under the direction of P. F. Anzhu and later by A. L. Chekanovskii (1873–75) and E. V. Toll’ (1885–86). In 1897 water-measuring observations were begun in Kirensk and Ust’-Kut, and in 1899, in Yakutsk and Vitim. From 1910 to 1915 the Lena team of the Amur Basin Waterways Administration conducted cartographic work on the Lena. Expeditions headed by F. A. Matisen (1919—20) and N. I. Evgenov (1921) compiled descriptions of the Lena from its mouth to Yakutsk. At present the Yakutsk Branch of the Siberian Division of the Academy of Sciences of the USSR is conducting systematic research on the Lena and rivers of the Lena basin.
REFERENCESKozhov, M. M. Presnye vody Vostochnoi Sibiri [Irkutsk] 1950.
Muranov, A.P. Velichaishie reki mira. Leningrad, 1968.
Zalogin, B. S., and N. A. Rodionov. Ust’evye oblasti rek SSSR. Moscow, 1969.
Domanitskii, A. P., R. G. Dubrovina, and A. I. Isaeva. Reki i ozera Sovetskogo Soiuza. Leningrad, 1971.
Mostakhov, S. E. Reka Lena. Yakutsk, 1972.
I. V. POPOV