Hydrological response to twenty-first century climate change in the Amu Darya Basin, Central Asia

Amu Darya River, a transboundary river originated in the high mountains of Central Asia, provides water resources for 43 million people. The river is a hot spot for research and of high tension and conflicts among nearby countries. Climate projections from 20 Earth System Models (ESMs) under SSP1–2.6, SSP2–4.5, SSP3–7.0 and SSP5–8.5 climate scenarios archived in CMIP6 were statistically downscaled and bias corrected and were used to force the Variable Infiltration Capacity (VIC) hydrological model coupled with glacier melting scheme to analyze climate change impact on streamflow during 2020–2100. Our analysis focuses on the long-term streamflow changes, seasonality of streamflow, streamflow variability, and extreme streamflow. Our study shows that although annual snowmelt streamflow sharply decreases, the modeled annual total streamflow continues to rise until the middle or the end of the century caused primarily by a positive change in rainfall and accelerated glacier melt. In this melt-water -dominated basin, the future hydrology largely depends on the rainfall and glacier melt. At the seasonal scale, the earlier onset of snowmelt causes total streamflow increases in spring and early summer, but little changes in the timing of peak streamflow. Analysis of annual maximum daily flows and streamflow variability reveals increases in the intensity and frequency of extreme streamflow event and a much larger year-to-year variability due to the reduced buffering effects of snowmelt and the gradually increased contribution from rainfall. These projections indicate that mitigation measures of ensuring water security should focus on coping with seasonal streamflow shifts, high annual streamflow variability and enhanced extreme events. • The future hydrology largely depends on the precipitation and glacier melt. • Peak timing of seasonal rainfall and snowmelt streamflow will shift significantly. • Increasing maximum daily streamflow implies for preparedness for flood extremes.