Kura (Caspian Sea) emptying into the Caspian Sea at Neftçala. Most of the Kura River runs in the broad and deep valley between the Greater Caucasus and Lesser Caucasus mountains, and the major tributary, the Aras, drains most of the southern Caucasus and the mountain ranges of the extreme northern Middle East. The entirety of Armenia and most of Azerbaijan are drained by the Kura River, but the Kura does not pass through Armenia at all. Also in the Kura watershed are Turkey, Georgia, and a bit of northern Iran. Most of the elevation change in the river occurs within the first .
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