Black Sea–Caspian Steppe 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
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