Mean monthly river flow data are available for the Kura, Samur, Sulak, Terek, Volga and Ural rivers. The Table shows the mean annual inflows recorded for these rivers for 1936-96. There are no data for the Iranian rivers but these – in combination with other smaller rivers – are thought to contribute about 10 km3 per year, with groundwater adding a further 4 km3 per year. On the basis of the 1936-96 period, the mean annual inflow to the sea is therefore estimated at 280 km3/year.

  Recorded mean annual inflows to the Caspian Sea

Running the various climate model scenarios, it seems that for the Volga basin, runoff into the Caspian Sea will increase, peaking earlier than at present. This is because the warmer temperature will mean more rain than snow, which will run off quickly since soil moisture capacity will be exceeded. In the Ural basin, the runoff generated by the increased rainfall predicted for this basin is also expected to peak in April rather than May. The more southern Terek and Kura rivers are expected to produce rather less runoff than present because precipitation is likely to be less and evaporation will increase, meaning that less water will be available to flow to the sea.

Variability in monthly inflows to the Caspian Sea