Analysis of rapidly decreasing discharge in the transboundary Amudarya River, Central Asia: considering climate change and human impacts

The livelihoods of millions of people from five countries rely on the water resources of the transboundary Amudarya River basin, one of the most important freshwater systems in Central Asia. However, climate change (CC) and human activities (HA) have substantially altered the hydrological processes in the basin. This study provides one of the first comprehensive impact assessments of CC and HA on streamflow changes by analysing 90 years of simulated streamflow in this climate data-scarce region, using the hydrological modeling approach and climate elasticity. The data limitations were addressed by integrating multiple sources, including local and global datasets. The CC and HA’s impacts were separately quantified at 29 sites across all the main Amudarya tributaries for 1951–2020 relative to 1931–1950. The results showed a substantial increase in temperature (0.51–0.83 °C) and precipitation (6–13%) in the entire basin. Streamflow decreased by 54–77% in the middle and lower reaches. Attribution analysis showed that human activities were the dominant driver of this decline, contributing 114–120% of the net reduction, while climate change partly offset the decline by increasing streamflow by 14–20%, mainly through increased precipitation. In the headwater region, streamflow decreased by 22%, with human activities contributing 140% of the net decline, offsetting the positive contribution from climate change. Major tributaries, including the Vakhsh, Kunduz, Kofirnihon, Surkhandarya, Zeravshan, and Qashqadarya, showed streamflow reductions of 4–34%, primarily attributed to HA. Climate elasticity revealed precipitation as the most sensitive element in the region, with an elasticity of 1.25. These latest and comprehensive findings provide valuable insights for improving water resources planning and management in the region under changing climatic and anthropogenic pressures.