Lena (Evenki, Ölüöne; Yakut, Ulakhan-Yuryakh – big river) – a river in eastern Siberia, one of the great rivers of Russia and the globe. By water content it is the sixth largest in the world. The length is 4,400 km; the basin area is 2,490,000 km2. It flows through the Irkutsk region and the Republic of Sakha (Yakutia). The L. originates from a small lake on the western slope of the Baikal Mountains and runs into the Laptev Sea at 73°N. The L. basin is located in taiga and tundra and a small portion north of 71°N in forest tundra. Permafrost soils are widely spread.
According to the nature of the valley and the riverbed, the Lena is divided into three major areas: the upper, from the source to the inflow to the Vitim; the middle, between the mouths of the Vitim and the Aldan; and the lower, from the inflow to the Aldan to the mouth of the Lena. The upper Lena is rapid mountain river flowing through a deeply incised narrow valley with rocky shores and rock cliffs closing to the water, the so-called cheeks (“Drunken Bull” and others, 237 km below Kirensk). The large right tributary is the Kirenga. On the Shishkin rocks (near the village of Shishkino), there are well-preserved paintings of people and animals, hunting scenes, etc. made by the ancient inhabitants of the basin.
In its middle reaches, the Lena is a deep river, especially after the influx into the Olyokma, with the width of the channel up to 2 km; the valley is up to 30 km. At this section the Lena takes major tributaries: on the right, the Vitim, the Big Patom, the Olyokma, and the Chara, and on the left, the Nyuya. Below the city of Uritsk, almost a 200 km section of the Lena Pillars begins – a wonderful creation of nature. The river here constantly undermines the limestone plateau; the shore breaks steeply, forming a chaotic pile of rocks resembling ruins of castles, minarets, columns, etc.
The lower Lena flows within the Central Yakutia lowland. Its valley extends to 20–25 km with numerous lakes and swamps. Here the Lena meets with its major tributaries – the Aldan (right) and the Viluy (left). Then the valley narrows. On the right bank of the Lena, there are spurs of the Verkhoyansky Ridge. From the village of Bulun, the river flows between the Kharaulakh Mountains and the Czekanowski Ridge in a narrow valley (up to 2 km). The mouth area of the Lena belongs to the delta type. It includes the largest river delta in Russia and a vast sea coast. 130 km from the mouth, the Lena is divided into numerous arms forming a vast delta of approx. 30,000 km2 (the second place after the delta of the Mississippi). The largest arms of the delta are the Trofimovskaya arm (delivers to the sea up to 70 % of river water), the Olenyokskaya arm, and, the most important for shipping, the Bykovskaya arm with a length of 106 km (links the L. with the Bay of Tiksi).
By the water content, the Lena takes second place after the Yenisei among Russian rivers. The average annual water flow is 17,000 m3/s, the maximum is 200,000 m3/s, and the minimum is 366 m3/s. The average annual runoff to the Laptev Sea is approx. 540 km3. The solid runoff is approx. 12 million tons.
By the nature of the water regime, the Lena refers to the rivers of the East Siberian type and has a stretched snow flood and rain floods. The ice formation in the upper reaches occurs from late October to mid-May and in the lower reaches from late September to early June. The ice cover of the Lena and its tributaries is used as winter roads for motor transport. There is a regular ice crossing near Yakutsk extending the period of land communication between the right and left banks of the river for 1.5–2 months. Spring floods and summer–autumn rain floods (80–90 % of the annual flow fall on a warm part of the year) are very indicative. Ice opening leads to frequent powerful ice blocks with a water level increase of 10–15 m. Ice buildups are very distinctive for the Lena Basin.
Navigation on the Lena existed since 1855. The first steamship, which came from the sea to the mouth of the Lena, was the steamer “Lena,” accompanied by “Vega” of the expedition of N. A. E. Nordenskiöld while sailing through the Northern Sea Route along the coast of Siberia in the 1878–1879. Currently, the Lena remains the main transportation artery of Sakha–Yakutia. In floods, the Lena is navigable from Kachug; regular navigation is from Ust-Kut (Osetrovo). The major ports and berthing areas are Kachug, Zhigalovo, Ust-Kut, Kirensk, Lensk, Olyokma, Pokrovskiy, Yakutsk, Sangar, Zhigansk, and Bulun. The Kirenga, the Viluy, the Vitim, the Olyokma, and the Aldan are navigable tributaries. Exit from the Lena to the sea is through the port of Tiksi, built in 1934 on the Northern Sea Route.
Rivers of the Lena Basin have large reserves of hydropower (Viluiskaya and Mamakanskaya HPP) and minerals. There are mines of gold (in the Aldan), diamonds (Vilyui Basin), coal, natural gas, iron ore, mica, rock salt, and woods. In the lower reaches of the Lena, there are commercial fishing areas, whitefish, Siberian whitefish, white salmon, perch, trout, and burbot; in the upper reaches, there is a less valuable fish of the commercial importance – grayling, dace, pike, and perch.