Vilyuy

The Vilyuy (Вилю́й; Бүлүү, Bülüü, ) is a river in Russia, the longest tributary of the Lena. About 2650 km long, it flows mostly within the Sakha Republic. Its basin covers about 454000 km2.

History
The river is first mentioned in the 17th century in connection with the Russian conquest of Siberia. In 1634, Russian Cossacks, headed by Voin Shakhov, established a winter settlement at the confluence of the rivers Vilyuy and Tyukyan. This settlement served as the administrative center of the area for several decades, after which it was moved to the Yolyonnyokh area 45 km down by the Vilyuy, where the ostrog (fortified settlement) of Olensk (now Vilyuysk) was founded in 1773.

In the 1950s, diamond deposits were discovered in the area, about 700 km from its mouth. This led to the construction of the Mir Mine, together with access roads and an airport, and the Vilyuy Dam complex to generate power needed for the diamond concentrators.

Geography
The Vilyuy has its sources in the Vilyuy Plateau, part of the Central Siberian Plateau, in the Evenkiysky District (Krasnoyarsk Krai) and, flowing east, soon enters Sakha. It turns towards the south and southeast in the Central Yakutian Lowland, then back towards the east, and finally enters the Lena about 350 km downstream of Yakutsk, near Sangar. The Ust-Vilyuy Range rises above the facing bank of the Lena, opposite the mouth of the Vilyuy.

To the west of the Vilyuy and Chona is the Nizhnyaya Tunguska basin. The Vilyuy basin is sparsely populated. Small settlements along the river include Vilyuysk, Verkhnevilyuysk, Suntar, Ekonda and Nyurba.

Tributaries
The main tributaries of the Vilyuy are the Ulakhan-Vava, Chirkuo, Chona, Chybyda, Ulakhan-Botuobuya, Ochchuguy-Botuobuya, Tangnary, Kempendyay, Tonguo and Bappagay on the right; and the Sen, Lakharchana, Akhtaranda, Ygyatta, Markha, Tyukyan, and Tyung on the left.

Geology
Vilyuy is associated with geological formations Yakutsk-Vilyuy Rift (Vilyuy Rift Basin) and Yakutsk-Vilyuy LIP (large igneous province), also known as Vilyuy Traps.