ASSESSMENT OF SPRING FLOOD RUNOFF IN THE ZHAIYK-CASPIAN WATER MANAGEMENT BASIN: CURRENT STATE AND SCENARIO FORECAST

This study presents a comprehensive analysis of the characteristics of spring runoff in the Zhaiyk-Caspian water management basin for the modern period, as well as an assessment of projected changes for the horizons of 2030, 2040, and 2050 based on CMIP6 climate scenarios (SSP3-7.0 and SSP5-8.5). The analysis of observations from 34 hydrological stations revealed a decrease in spring runoff volume of up to 35 %, a reduction in flood duration, and a decline in peak discharge on certain rivers of up to 45 %. It was established that rising air temperatures, an increased frequency of thaws, and reduced autumn soil moisture contribute to lower peak discharges and a transformation of the seasonal runoff regime. Scenario-based projections demonstrated pronounced spatial heterogeneity: some rivers are expected to experience an increase in maximum runoff of up to 72 %, while others show a steady decrease of up to 35 %. These findings highlight the necessity of transitioning to an adaptive water resources management system that takes into account the regional characteristics of river basins and the high sensitivity of small and medium-sized streams to climate change.