Editing Ob (section)

==Geography==
[[File:Operational Navigation Chart C-4, 4th edition.jpg|thumb|left|Map including the mouth of the Ob River]]
The Ob forms {{convert|25|km|abbr=on}} southwest of [[Biysk]] in [[Altai Krai]] at the confluence of the [[Biya (river)|Biya]] and [[Katun (river)|Katun]] rivers. Both these streams have their origin in the [[Altai Mountains]], which gradually give way to the [[Ob Plateau]].<ref name="GSE">[https://www.booksite.ru/fulltext/1/001/008/092/860.htm Приобское плато] {{Webarchive|url=https://web.archive.org/web/20220702034243/https://www.booksite.ru/fulltext/1/001/008/092/860.htm |date=2022-07-02 }}; ''[[Great Soviet Encyclopedia]]'' in 30 vols.  — Ch. ed. [[A.M. Prokhorov]]. – 3rd ed. – M. Soviet Encyclopedia, 1969–1978. {{in lang|ru}}</ref> The Biya has its sources in [[Lake Teletskoye]] and the {{convert|700|km|mi}} long Katun in a glacier on [[Mount Byelukha]].<ref name="EB1911"/>

The Ob itself is in Russia. Its tributaries extend into northern [[Kazakhstan]], a western corner of China and a tiny upland parcel of the western tip of Mongolia, where the wider borders match the drainage basin almost precisely. The river splits into more than one arm after the large [[Irtysh]] flows into it at about 69° E. Originating in China, the Irtysh is the furthest source of the Ob. From their respective sources to the confluence, the Irtysh measures 4,248 kilometers (2,640&nbsp;mi) and the Ob 2,538&nbsp;km (1,577&nbsp;mi). Other noteworthy tributaries are: from the east, the [[Tom (river)|Tom]], [[Chulym (Ob)|Chulym]], [[Ket (river)|Ket]], [[Tym (Ob)|Tym]] and [[Vakh]] rivers; and, from the west and south, the [[Vasyugan]], Irtysh (with the [[Ishim (river)|Ishim]] and [[Tobol]] rivers), and [[Severnaya Sosva]].

The Ob zigzags west and north until it reaches 55° N, where it curves to the northwest, south of the [[Siberian Uvaly]], at the western end of which it bends northwards, wheeling finally eastwards into the [[Gulf of Ob]], a {{convert|1000|km|mi|abbr=off|adj=mid|-long}} bay of the [[Kara Sea]], separating the [[Yamal Peninsula]] from the [[Gyda Peninsula]].

The combined Ob-Irtysh system, the [[List of rivers by length|fourth-longest river system]] of Asia (after [[Yenisei]], and China's [[Yangzi]] and [[Yellow River|Yellow]] rivers), is {{convert|5410|km|mi}} long, and the area of its basin {{convert|2990000|km2|mi2}}.
The river basin of the Ob consists mostly of [[steppe]], [[taiga]], swamps, [[tundra]], and [[semi-desert]] topography. The floodplains of the Ob are characterised by many tributaries and lakes.
The Ob is icebound at southern [[Barnaul]] from early in November to near the end of April, and at northern [[Salekhard]], {{convert|150|km|abbr=on}} above its mouth, from the end of October to the beginning of June.{{Update inline|reason=likely climate change since 1911|date=October 2023}}<ref name="EB1911"/>
The Ob River crosses several climatic zones. The upper Ob valley, in the south, supports grapes, melons and watermelons, whereas the lower reaches of the Ob are Arctic tundra. The most temperate climates on the Ob are at [[Biysk]], Barnaul, and [[Novosibirsk]].

[[File:Yenisei Ob Kara Sea.jpg|thumb|Yenisei and Ob (right) flow into Kara Sea]]