Ob River

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Ob River
Ob-Irtysh watershed
Origin	Altai Krai
Mouth	Kara Sea
Basin countries	Russia
Length	3,650 km (2,268 mi) from the head of the Katun River; 5,410 km (3,362 mi) from the head of the Irtysh River
Source elevation
Avg. discharge	12,500 m³/s (441,500 ft³/s)
Basin area	2,972,497 km² (1,131,273 mi²)

Ob River (Russian: Обь), also Obi, is a major river in West Siberia, Russia, the country's fourth longest.

It is known to the Khanty people as the As, Yag, Kolta and Yema; to the Nenets people as the Kolta or Kuay; and to the Siberian Tatars as the Umar or Omar.

The Ob is formed eight miles southwest of Biysk in Altai Krai by the confluence of the Biya and Katun rivers. Both these streams have their origin in the Altay Mountains, the Biya issuing from Lake Teletskoye, the Katun, 80 mi long, bursting out of a glacier on Mount Byelukha. The Ob zigzags west and north until it reaches 55° N, where it curves round to the northwest, and again north, wheeling finally eastwards into the Gulf of Ob, a long (600 mi) bay of the Kara Sea, which adjoins the Arctic Ocean.

The river splits into more than one arm, especially after joining the large Irtysh tributary at about 69° E. Originating in China, the Irtysh is actually longer than the Ob from their sources to the point of their confluence. From the source of the Irtysh to the mouth of the Ob, the river flow is the longest in Russia at 5,410 km. Other noteworthy tributaries are: from the east, the Tom, Chulym, Ket, Tym and Vakh rivers; and, from the west and south, the Vasyugan, Irtysh (with the Ishim and Tobol rivers), and Sosva rivers.

The navigable waters within its basin reach a total length of 9300 mi. By means of the Turn, an affluent of the Tobol, it secures connection with the Ekaterinburg-Perm railway at Tyumen, and thus is linked to the Kama and Volga rivers in the heart of Russia. Its own length is 3700 km (2,260 mi), and the area of its basin 2,600,000 km² (1,125,200 mi²).

The combined Ob-Irtysh system, the third-longest river system of Asia (after China's Yangtze and Yellow rivers), is 5,410 km (3,362 mi) long. The largest river port is on the Irtysh in Omsk, with a link to the Trans-Siberian Railway.

In the late 19th century, a system of canals, utilizing the Ket River, 560 mi long in all, was built to connect the Ob with the Yenisei, but soon abandoned as being uncompetitive with the railway.

The river basin of the Ob exists mostly of steppe, taiga, swamps, tundra, and semi-desert topography. The floodplains of the Ob are characterized by many tributaries and lakes.

The Ob is ice-bound at southern Barnaul from early in November to near the end of April, and at northern Salekhard, 100 miles above its mouth, from the end of October to the beginning of June. Its middle reaches have been navigated by steamboats since 1845.