Black Sea–Caspian Steppe 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
Caspian Sea is the saline eastern inlet of the Caspian, which is part of Turkmenistan and at times has been a lake in its own right due to the isthmus that cuts it off from the Caspian. Differences between the three regions are dramatic. The Northern Caspian only includes the Caspian shelf, and is very shallow; it accounts for less than 1% of the total water volume with an average depth of only . The sea noticeably drops off towards the Middle Caspian, where the average depth is . The Southern Caspian is the deepest, with oceanic depths of over , greatly