The West Siberian Plain is the largest and flattest plain on earth. Actually, it is somewhat concave, because the soft soils were compressed under glaciers. This concave shape, combined with the fact that the Ob flows northward, produces huge ice jams and a great deal of springtime flooding throughout the mid- and lower reaches of the Ob.

The Ob River is the fifth longest in the world when measured from the headwaters of the Irytsh (5,410 miles); when measured from the headwaters of the Katun it is 3,650 miles long.

Down south, upriver near Barnaul, the river thaws in late April, while up north, near its mouth, the Ob doesn't thaw until early June. This means that when the upriver reaches of the river thaw in the spring, the melt water meets an ice jam and backs up into the lowlands.





The gigantic marshland that is formed by flooding in the lowlands is one of the reasons why it is so difficult to get across Siberia. But it is also the reason that there is so much oil and gas. Geologically, the basement structure came into being 1.6-1.7 billion years ago and has undergone prolonged subsidence and deposition, resulting in Mesozoic-Cenozoic basin fill on top of a Paleozoic basin. The 66 fields discovered since the 1960s in the northern West Siberian basin contain at least 22 trillion m³ of proved gas, which is almost 1/3 of world's reserves. Half of these fields are giants (> 85 billion m³) and include the largest and second-largest gas fields in the world.

You can see the location of the fields in the Google Earth night view below (NASA Earth City Lights from the Google Earth Gallery) as well as the location of the Kuzbass coalfields and the Trans-Siberian Railroad, all of which are lit up while the rest of Siberia is without conspicuous artificial lighting. (You can explore this in the Google Earth KML file in the attachment section at the bottom of the page.)

The Katun, Biya, and Ob Rivers and Lake Teletskoye in the Altai Republic

In contrast to the marshy lowlands of the middle and lower Ob River, its headwaters are in rocky mountainous regions to the south.

Left: location of proposed dam on the Katun River (only partially completed). The Katun joins the Biya River to form the Ob just north of the Altai Republic near the city of Biisk.

The proposed dams on the Katun River were part of the effort by Soviet planners to divert water from Siberian rivers to supplement the flow to the Aral Sea.

In addition, a great many significant cultural resources would have been lost. The combination of scientific, cultural, and Indigenous values sparked a massive protest against the dams in the final years of the Soviet Union. We documented this in our paper The Sacred and the Scientific: Traditional Ecological Knowledge in Siberian River Conservation

Lake Teletskoye drains into the Biya River, which along with the Katun, forms the headwaters of the Ob River. Like Lake Baikal, Lake Teletskoye is a rift lake with a single outflow river (the Biya). 

Sources