Hydrological Drought Risks in the Balkhash-Alakol Basin Under Changing Climate Conditions

This study investigates the formation, development, and spatio-temporal variability of meteorological and hydrological droughts in the Balkhash-Alakol water management basin under current climate change and increasing anthropogenic pressure. The analysis is based on long-term observations of precipitation, air temperature, and river discharge from 10 meteorological and five hydrological stations representing different natural–climatic zones of the region. Drought conditions were quantified using the SPI, SPEI, and SDI indices, allowing for a comparative assessment of drought characteristics while accounting for precipitation deficits, temperature-driven evaporation, and water-balance processes. Since the 1970s, the basin has experienced a pronounced warming trend, particularly in winter and spring, accompanied by more frequent hot days and longer heat waves. These changes enhance evaporation and contribute to moisture deficits. A shift toward reduced summer precipitation in the latter part of the study period further increases the likelihood of hydrological drought and reduces the stability of summer–autumn low-flow conditions. All three drought indices indicate an increase in the frequency, duration, and intensity of drought events, especially since the 1990s. Lag-correlation analysis reveals a relatively short lag from meteorological to hydrological drought, with the strongest correlations between SPI-12/SPEI-12 and SDI-12 occurring at about 2–3 months. Anthropogenic water abstraction and river regulation, particularly in the Ile River basin, further amplify the sensitivity of water resources to climatic anomalies. The results improve understanding of drought development mechanisms in the Balkhash-Alakol basin and support a more robust assessment of water-resource vulnerability under ongoing climate change.