The Caspian Sea has 10 large gulfs: Comsomolets, Mangishlag, Kazakh, Gara-Boghaz-Gol, Turkmenbashi (former Krasnovodsk), Turkman, Gizilaghage, Astrakhan, and Gizlar. Iranian Caspian sector has two large gulfs: Hirkan (former Astrabad) and Anzali (former Pahlavi).

The most notable and large Caspian gulf is Gara-Boghaz-Gol. Having been controlled by the Caspian Sea level fluctuation the gulf area varies recurrently. Nowadays its surface embraces 25,000 sq km. The gulf area is connected to the Caspian Sea through the new 10-10.5 km long narrow channel which width varies from 110 to 300 m. Gara-Boghaz-Gol water level has always been lower than the Caspian one. The discrepancy between the gulf's water level and that of the sea depends on the latter and varies in the range from 2 to 6 m. Water continuously flows through the channel, however, it entirely evaporates from the gulf surface. Every year approximately 8-103 km of water flows into the gulf that is 20-3003  m of water per second (recently acquired data indicates even greater values). This water brings some 150,000 tons of dissolved salts into the gulf from the sea. During 1980-1984 the gulf remained isolated from the sea via a built-up dam. About 1500 mm of waters evaporates every year from its surface, whereas the amount of precipitation does not exceed 70 mm/yr. Therefore the gulf's water actually resembles salt-saturated solution (strong solution) which salinity reaches up to 300 ppm and it represents a single basin with the marine evaporates. Gara-Boghaz-Gol gulf is rich with such mineral salts as mirabilite, halite, astrakhanite etc. Currently, sulphite, bisulfite, epsomite, glauberite, medical and marine salts as well as chlorous magnesium production is underway there.


Over 130-rivers flow into the Caspian Sea and just 9 of their mouths are referred to as deltas. The biggest of these rivers is 3531 km long Volga River which average run-off approximates 251-254 km3 Another large river flowing into the Caspian Sea from Russia drainage area is Terek River (with average run-off varies from 8.5 to 11.4 km3).

The largest rivers flowing into the Caspian Sea from Azerbaijan territory are as follows: Rur River (average annual run-off measures 16 km3; Lankaranchay, Sumgayitchay, Valvalachay, Gudialchay, Astarachay (bordering river between Azerbaijan and Iran), and Samur River bordering Azerbaijan and Russia (2.7 km).

River drainage is almost absent along the Caspian eastern margin. Both Ural (run-off - 8.1 km3) and Emba Rivers flow into the Caspian Sea from Kazakhstan territory. In the 1920s, the Emba River had a vast delta with several distributary channels. Sea level drop that took place during the 1930s caused Emba river to disappear among the coastal sands. Nowadays, this river reaches the Caspian Sea only during years prone to atmospheric precipitation.

A single river flowing continuously in Turkmenistan is a 635 km long Atrek River, of which 500 km falls into Iran territory. Its drainage area measures 26.7 km2 Atrek River average annual run-off within Turkmenistan area amounts to 240 M km3. Frequently river is dried in its lower watercourse and reaches the Caspian Sea only during spring seasons. The Caspian Sea embraces only 12% of the total Iranian drainage area and captures only 5% of its run-off. Relatively large rivers are as follows: Safidrud 720 km long (Agh-chay), Haraz, Polerud, Babol, Calus, Hirkan, Techan and Talar. Of 1040km long Araz River, just 300 km serves as a borderline between Azerbaijan and Iran. The river changes its watercourse direction from the northernmost Iran bordering point to interflow with Kur River watercourse.


The major harbours within the Caspian Sea are as follows: Baku harbour (the largest one), Turkmenbashi, Astrakhan, Mahachgala, Aktau, Atiran, Bandar-Anzali, Noushahar.