Study on the coupling processes of glaciers, snow and runoff in the Pamir Plateau

Study region The Vakhsh River Basin, the largest tributary of the Amu River, is located in the Pamir Mountains in Central Asia. Research focus The Vakhsh River Basin, contributing ∼24% of the Amu Darya’s discharge and over 90% of Tajikistan’s hydropower, provides a key case for studying climate-driven streamflow changes. However, due to observational constraints, the coupling among glaciers, snow, and runoff in this region remains poorly understood. Therefore, this study employs the SWAT-Glacier-SRD model under a multi-objective calibration framework to investigate hydrological responses to climate change. New hydrological insights Results indicate that the model could well simulate hydrological processes in this catchment with daily NSE being 0.81 and 0.78 during the calibration and validation periods. During 1971–2019, streamflow increased significantly (1.57 mm yr⁻¹), while its composition remained stable, dominated by snowmelt (58.2%), followed by rainfall (30.5%) and glacier melt (11.3%). At the seasonal scale, the contribution of rainfall increased in early spring. Further analysis showed that streamflow timing is highly sensitive to climate conditions, with warmer, drier conditions leading to earlier and more dispersed flow, and colder, wetter conditions producing later and more concentrated flow. Despite significant warming in this region, streamflow timing shows only a slight, insignificant advance (−0.129 d yr⁻¹), likely due to compensatory precipitation effects, but this stability may not persist under intensified warming. This study provides a reliable framework for simulating cryosphere–hydrology processes in Central Asian basins.