Siberia’s Ob and Irtysh forge the world’s seventh-longest system
The Ob forms in western Siberia where the Biya and Katun meet from the Altai, then partners with the Irtysh in a combined course measuring 5,410 kilometres—ranked seventh among the planet’s longest river systems. Novosibirsk—Siberia’s largest city and Russia’s third—straddles the banks where the Trans-Siberian Railway crosses.
The Ob is the westernmost of Siberia's three great Arctic-bound rivers, alongside the Yenisei and the Lena. Its farthest source is actually the Irtysh, which rises in China and runs 4,248 kilometres to the junction, compared with 2,538 for the Ob itself above that point. Tributaries reach into northern Kazakhstan, a corner of China and a sliver of western Mongolia, draining a basin of about 2,990,000 square kilometres. The Katun, one of its two headstreams, flows some 700 kilometres from a glacier on Mount Byelukha. Near its end the river turns east and empties into the Gulf of Ob, a Kara Sea inlet stretching 1,000 kilometres that splits the Yamal and Gyda peninsulas.
The river crosses several climate zones: grapes and melons grow along its upper valley, while its lower reaches are tundra. Ice locks it at Barnaul from early November until late April, and at Salekhard, 150 kilometres from the mouth, from late October to early June. More than 50 fish species live in it, and navigable channels across the basin total about 15,000 kilometres.
Novgorod traders reached the lower Ob by at least the eleventh century along two routes from Ustyug. Beryozov, Obdorsk and Surgut were founded late in the sixteenth century, steamboats worked the middle river from 1845, and 49 steamers plied it by 1916. A 900-kilometre canal system linking the Ob with the Yenisei was built in the late nineteenth century but soon abandoned because railways were cheaper.
A dam near Novosibirsk in 1956 created what was then Siberia's largest reservoir. A vast Soviet plan to divert Ob and Irtysh water toward Central Asia and the Aral Sea was dropped in 1986. Oilfields of the West Siberian basin now pollute the river: in its lower reaches petroleum levels exceed permitted limits nine to ten times and dissolved oxygen is a quarter of normal.
Source: Ob
