Abstract
The possibility of making scenario forecasts of water-resources of the Zhayik-Caspian rivers’ basin on separate water management areas is considered. To characterize the modern climate, the period 1980-2000 was used as the initial one. To characterize the climate of the 21st century, the projects of climate updated until 2050 were used, which obtained in Kazgidromet by S.A. Dolgikh. The basis of the forecasting method consists of the dependence of the spring flood runoff from the degree of moistness of soil, and dependence from the amount of water reserves kept in the snow before melting begins. Takethe sum of autumn precipitation from September-October as an indicator of degree of the indirect soilmoistness, and take the amount of precipitation from November-March as the indicator of the amount ofwater reserves kept in the snow. The total annual runoff is determined depending on the magnitude ofthe spring runoff. There is a close relationship between these characteristics of the runoff. The quality ofthe predictive dependence is tested by using the S / Ϭ criterion. Satisfactory dependence was obtainedfor 10 sites. Based on scenario forecasts of the climate of the Zhayik-Caspian water management’s basinfor the period up to 2050, forecasts of water resources of the individual sites were compiled for 2025,2030, 2035, 2040, 2045, 2050. In general, according to the Zhayik-Caspian basin, an average increasein runoff of 5-7% is expected on two scenarios for all the years. In some areas, the runoff may increaseup to 10-15%. In the basin of the river Sagiz, on the contrary, one should expect a decrease in runoff to80%. The predicted dependence is not obtained for the site 05.03.09.00, because the expected amountof runoff depends on the amount of water flowing to an anabranch of the Volga river.