Irtysh in the context of "Tobol"

A tributary, or an affluent, is a stream or river that flows into a larger stream (main stem or "parent"), river, or a lake. A tributary does not flow directly into a sea or ocean. Tributaries, and the main stem river into which they flow, drain the surrounding drainage basin of its surface water and groundwater, leading the water out into an ocean, another river, or into an endorheic basin.

The Irtysh, a tributary of the Ob river, is the longest tributary river in the world with a length of 4,248 km (2,640 mi).The Madeira River is the largest tributary river by volume in the world with an average discharge of 31,200 m/s (1.1 million cu ft/s).

Omsk (/ˈɒmsk/; Russian: Омск, IPA: [omsk]) is the administrative center and largest city of Omsk Oblast, Russia. It is situated in southwestern Siberia and has a population of over one million. Omsk is the third largest city in Siberia after Novosibirsk and Krasnoyarsk, and the twelfth-largest city in Russia. It is an important transport node, serving as a train station for the Trans-Siberian Railway and as a staging post for the Irtysh River.

During the Imperial era, Omsk was the seat of the Governor General of Western Siberia and, later, of the Governor General of the Steppes. For a brief period during the Russian Civil War in 1918–1920, it served as the capital of the anti-Bolshevik Russian State and held the imperial gold reserves.

Khanty (also spelled Khanti or Hanti), previously known as Ostyak (/ˈɒstjæk/), is a branch of the Ugric languages composed of multiple dialect continua. It is varyingly considered a language or a collection of distinct languages spoken in the Khanty-Mansi and the Yamalo-Nenets Autonomous Okrugs in Siberia. It belongs to the wider Uralic language family. There were thought to be around 7,500 speakers of Northern Khanty and 2,000 speakers of Eastern Khanty in 2010, with Southern Khanty being extinct since the early 20th century. The number of speakers reported in the 2020 census was 13,900.

The Khanty language has many dialects. The western group includes the Obdorian, Ob, and Irtysh dialects. The eastern group includes the Surgut and Vakh-Vasyugan dialects, which in turn are subdivided into 13 other dialects. All these dialects differ significantly from each other by phonetic, morphological, and lexical features to the extent that the three main "dialects" (northern, southern and eastern) are mutually unintelligible. Thus, based on their significant multifactorial differences, Eastern, Northern and Southern Khanty may be considered separate but closely related languages.

Western Siberia or West Siberia (Russian: Западная Сибирь, IPA: [ˈzapədnəjə sʲɪˈbʲirʲ]; Kazakh: Batys Sıbır, IPA: [bɑˈtə̥s sɘˈbɘr]) is a region in North Asia. It is part of the wider region of Siberia that is mostly located in the Russian Federation, with a Southern part in Kazakhstan. It lies between the Ural region and the Yenisei River, which conventionally divides Siberia into two halves.

Western Siberia covers an area of 2,500,000 square kilometers (970,000 sq mi), nearly 80% of which is located within the West Siberian Plain. The largest rivers of the region are the Irtysh and the Ob. All major rivers of Western Siberia belong to the Kara Sea basin.

The Ob (/ˈɒb/; Russian: Обь) is a major river in Russia. It is in western Siberia, and with its tributary the Irtysh forms the world's seventh-longest river system, at 5,410 kilometres (3,360 mi). The Ob forms at the confluence of the Biya and Katun which have their origins in the Altai Mountains. It is the westernmost of the three great Siberian rivers that flow into the Arctic Ocean (the other two being the Yenisei and the Lena). Its flow is north-westward, then northward.

The main city on its banks is Novosibirsk, the largest city in Siberia, and the third-largest city in Russia. It is where the Trans-Siberian Railway crosses the river.