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
Black Sea is a marginal sea and is the world's largest body of water with a meromictic basin. The deep waters do not mix with the upper layers of water that receive oxygen from the atmosphere. As a result, over 90% of the deeper Black Sea volume is anoxic water. The Black Sea's circulation patterns are primarily controlled by basin topography and fluvial inputs, which result in a strongly stratified vertical structure. Because of the extreme stratification, it is classified as a salt wedge estuary. The Black Sea only experiences water transfer with the Mediterranean Sea, so all inflow and outflow occurs