Аңдатпа
Water scarcity during the growing season remains a major constraint for irrigated agriculture in Central Asia, particularly in transboundary river basins where water availability depends on mountain snow accumulation and melt processes. This study aims to assess how seasonal snow dynamics influence water availability in the Kuragaty sub-basin of the Shu river basin, with focus on downstream agricultural areas located in Kazakhstan and Kyrgyz Republic. Snow cover dynamics were derived from Sentinel-2 satellite imagery for elevations above 1000 m over the period from November to May, using a threshold-based snow detection approach. Evapotranspiration over agricultural lands was estimated from Landsat data using an energy balance model, while river discharge data from hydrometric stations were used to characterize the hydrological response. The results show a stable seasonal pattern of snow cover, with maximum extent observed in winter, where mean values exceed 55% and reach 59 ± 11.7% in December. In spring, snow cover rapidly decreases to 27.6 ± 12.7% in April and below 10% in May. The spring snow index (March-April) averages 37 ± 8.2%, reflecting strong interannual variability. Evapotranspiration follows a consistent seasonal cycle, increasing to 2.1 ± 0.6 mm/day in May and reaching peak values of up to 7.4 ± 1.2 mm/day in June. The total evapotranspiration during the growing season, averages 214.4 ± 24.2 mm. River discharge during this period shows moderate variability, with mean values of 4.26 ± 1.34 m3/s and peak flows occurring in early summer. A consistent positive relationship was observed between late-winter to early-spring snow cover and evapotranspiration during May-June, indicating that snowmelt contributes to water supply at the onset of the irrigation period. At the same time, evapotranspiration patterns are also influenced by vegetation development and increasing atmospheric demand, suggesting that snow dynamics act as an initial, but not the only, controlling factor.