The Caspian Sea - the largest on the planet closed lake occupying a large and deep continental depression within the most significant in Europe inland runoff. In early 2000, the level of its surface lay at around - 27 abs. meter, and the area is 393 km2 with a value of 78,600 km3 of water. Up to date, the total damage from the growth of the Caspian Sea is estimated hundreds of billions of rubles. In this regard, there was a lot of research on various aspects of the problem of instability level of the reservoir (the Caspian Sea), but there is still no clarity about the latter. The Caspian Sea forming is characterized by the repeated change of transgressive and regressive level phase with variety of magnitude and duration. It is known, in Pleistocene (last 700-500 thousand years) the level of the Caspian Sea has undergone large-scale fluctuations in the range of approximately 200 m from (-140) to (+50) abs. meter. In the period 1929-1941, the Caspian Sea surface sharply declined by almost 2m from (-25.88) up to