wcm.01.2026.01.08

Our study examines the impact of climate change on the hydrology of the Charvak Lake watershed in Uzbekistan, focusing on streamflow from the Pskem, Chatkal, and Koksu rivers during the 1990–2022 period. The analysis evaluated the contributions of snowmelt and glaciers to river flows while addressing modelling limitations, including the absence of dedicated land classes for snow cover and glaciers. This study, conducted under the CGIAR NEXUS Policy Innovation initiative, focused on hydrological modeling using the QSWAT+ tool to better understand these dynamics. Calibration efforts improved model performance, with statistical parameters indicating a correlation coefficient (R) of 0.77, a coefficient of determination (R²) of 0.59, and a percent bias (PBIAS) of –15%, demonstrating reasonable agreement between observed and simulated data. However, the Nash–Sutcliffe Efficiency (NSE) was low at 0.27, highlighting challenges in accurately simulating extreme flows during peak and low-flow periods. Mann–Kendall and Sen’s slope tests showed no statistically significant trends in streamflow for both simulated and observed flows (p = 0.69 and p = 0.31, respectively), though observed data suggested a slight potential increase likely linked to glacier melt.