Impacts of future climate change on runoff and its components for the Vanj river basin in the western Pamir

The Vanj River Basin (VRB) in Tajikistan is a glacierized catchment where meltwater is a crucial water source for irrigation, hydropower, and downstream ecosystems in Central Asia. Extensive glacier coverage makes basin runoff highly sensitive to climate change. This study employed the cryospheric‑hydrological model Spatial Processes in Hydrology (SPHY) to project streamflow under future climate scenarios. The model was calibrated for 2000–2010 and validated for 2011–2015 using European ReAnalysis (ERA5) data. Climate forcing was generated by downscaling ERA5 data and resampling Coupled Model Intercomparison Project Phase 6 (CMIP6) Global Climate Model outputs to the model resolution of 0.01 °× 0.01 °, followed by bias correction using observed data. Simulations were carried out for the historical (2000–2023), near‑ (2029–2052), mid‑ (2053–2076), and far‑future (2077–2100) periods under three Shared Socioeconomic Pathways (SSP1‑2.6, SSP2‑4.5, and SSP5‑8.5). Mean annual temperature is projected to rise by + 1.0 °C, + 2.3 °C, and + 5.5 °C under SSP1‑2.6, SSP2‑4.5, and SSP5‑8.5, respectively, by the end of the century. Glaciers are expected to lose –23 %, –27 %, and –77 % of their area, while annual runoff declines by –33 %, –32.7 %, and –17.3 %. The peak of snowmelt runoff is projected to shift from July to June, and seasonal flow variability is likely to intensify due to changing precipitation and temperature. These results highlight the urgent need for adaptive water management and sustainable hydropower planning in glacier‑fed catchments of Central Asia. • Vanj Basin glaciers projected to decline by 23–77% by 2100, threatening water security. • Total annual runoff expected to decrease by 17–33% by the end of the century. • Peak runoff shifts to June, reducing critical late-summer water availability. • Warming of +1.0°C to +5.5°C drives major hydrological changes across Central Asia.

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