Abstract
This study investigates hydrological variability and water stress dynamics in the Shu River basin, a semi-arid transboundary river system in Central Asia, under changing climatic and anthropogenic conditions. Using hydrological data from 2011 to 2024 collected at three key gauging stations (Kainar, Tashutkul, and Ulanbel), we analyzed temporal variations in river inflow, water balance components, and water stress indicators. A combination of statistical methods, including linear trend analysis, the Mann–Kendall test, Sen’s slope estimator, and the coefficient of variation, was applied to assess the direction, magnitude, and variability of hydrological changes. In addition, the Water Stress Index (WSI) and Environmental Flow Ratio (EFR) were used to evaluate pressure on water resources and ecological sustainability. The results reveal a consistent decline in river discharge across all observation sites, with the most pronounced decrease observed in downstream sections. Total inflow and river inflow show statistically significant negative trends, indicating a reduction in water availability over time. In contrast, local flow and water consumption exhibit no significant trends, suggesting relatively stable demand conditions. The WSI analysis indicates moderate to high water stress, with increasing variability and periodic exceedance of critical thresholds in recent years. Despite growing pressure on water resources, the EFR remains above ecological safety thresholds, indicating a certain resilience of the basin’s ecological system. Overall, the findings demonstrate that increasing water stress in the Shu River basin is primarily driven by declining water inflows rather than rising water consumption. The study highlights the importance of integrated water resource management strategies that address both climatic variability and anthropogenic pressures in transboundary river basins.