Importance of glacier shrinkage for sustaining runoff in Panj River of Pamir, Central Asia

Study region The study area is the Panj River basin, situated in the upper reaches of the Amu Darya basin. Study focus Glacier and snowmelt runoff are vital for sustaining streamflow in the Panj River Basin, a key cryospheric water source region in Central Asia. However, the impacts of glacier retreat, snow changes, and precipitation variability on long-term runoff remain unclear under global warming. This study applied the Hydrologiska Byråns Vattenbalansavdelning (HBV) model to quantify runoff components, including rainfall, snowmelt, and glacier runoff, and integrated the Budyko framework, scenario simulations, and glacier retreat experiments to assess runoff drivers and the hydrological response to glacier loss. New hydrological insights The results showed that total runoff, rainfall runoff, and snowmelt runoff exhibited significant decreasing trends during 1982–2020, whereas glacier runoff increased, reflecting a temporary compensation effect from enhanced glacier melt under climate warming. Meltwater runoff accounted for 67.9% of total runoff and played an important role in regulating streamflow, particularly during dry years. Attribution analysis revealed that runoff changes were mainly controlled by climatic factors (122.5%), with precipitation being the dominant driver, while human activities (−22.5%) partially offset the decline in runoff. Glacier retreat scenarios indicated that continued glacier loss would reduce summer meltwater supply and may alter the seasonal distribution of runoff, with potential implications for the stability of downstream water supply. The impacts of glacier change on mountain runoff processes and regional water resources provide a basis for understanding potential changes in downstream water availability in Central Asia.