Caspian Sea
The sea has a surface area of 371,000 km (143,200 sq mi) (not including the detached lagoon of Garabogazköl) and a volume of 78,200 km(18,800 cu mi). It has a salinity of approximately 1.2% (12 g/l), about a third of the salinity of most seawater.
Black Sea–Caspian Steppe
The region is about 900 km at its widest and about 500 km from north to south. Low rainfall makes the whole area grassland. Rainfall decreases to the east and north (20-30 inches in the west, 13 in Volgograd and 9 in Astrakhan). Most of the area is less than 500 feet in altitude, rising to over 1000 feet in the Stavropol Highland. The Manych Depression is not much more than 65 feet above sea level and the area around Astrakhan and part of Kalmykia is below sea level.
Rivers: Through the center runs the northwest-tending Kuma-Manych Depression. This was once a strait connecting the Black and Caspian Seas and is now marked by the Manych River which is basically a chain of lakes. It will probably be the route of the Eurasia Canal if that great engineering work is ever built. In the south the rivers that flow north from the Caucasus are caught by the west-flowing Kuban River and the east-flowing Terek River. Between these the rivers are caught by the Malka River which is an east-flowing tributary of the Terek. In the west, since the Caucasus Mountains run parallel and close to the Black Sea coast, no significant rivers from this area reach the Black Sea. The western point is the Taman Peninsula. North of the Taman Peninsula the Kuban River, the Beysug River and the Yeya Rivers reach the Sea of Azov, and the long Manych River and the shorter Sal River reach the lower Don. In the north much of the lower Don is under the Tsimlyansk Reservoir and the Volga has a broad flood plain and a large delta. North of the Manych Depression the low Ergeni Highland forms the watershed between the Don and Volga. It drops off quickly to the Caspian Depression. To the east of this the Sarpinsky Lakes are a chain of lakes in Kalmykia that would be a north-flowing river if there were more rainfall. On the east the only important rivers that reach the Caspian are the Volga, Kuma River and the Terek. In the center the Yegorlyk River and Kalaus River flow north to the Manych and the Kuma River flows northeast to the Caspian. In the east there are many shallow lakes. Since the land is flat and the rainfall barely sufficient for agriculture there are important irrigation canals, most leading from the Caucasus peidmont to the Manych Depression. The Great Stavropol Canal leads northeast from the Kuban to the Kalaus and beyond and the Nevinnomyssk Canal runs from the Kuban to the Egorlyk. The Kuma-Manych Canal feeds water from the Kuma to the East Manych and Chyornozemsky Canal irrigates the interior of Kalmykia. There numerous canals around the lower Terek.