Abstract
River runoff depends directly on climate conditions (e.g., temperature, precipitation and evapotranspiration), which affect water balance at the watersheds scale. The present work was conducted to investigate the impact of climate change on runoff in the Syrdarya River Basin, Central Asia. To assess the impact of climatic variation on runoff, the temporal trends of runoff were explored using the sensitivities of runoff to precipitation, temperature and potential evapotranspiration, and the aridity index was evaluated with the modified method of climate elasticity. The results showed that the average coefficients of sensitivity of runoff to precipitation and potential evapotranspiration were 2.4 and -1.4, and the sensitivity to temperature was -0.8 respectively, indicating that a 10% increase in precipitation or potential evapotranspiration would lead to a 24% increase or a 14% decrease in runoff, respectively. Additionally, the average coefficient of sensitivity of runoff to the aridity index varied from 0.65 to 2.8. The average coefficients of the sensitivity of runoff to climatic variation appeared to have an inverse relationship with the runoff coefficient, showing that the lower the river flow of the basin became, the more sensitive the runoff would be with respect to climatic variation. The results confirm the high sensitivity of river runoff in the Syrdarya River Basin to climatic changes. Precipitation was identified as the dominant factor controlling runoff formation, whereas an increase in potential evapotranspiration contributes to a reduction in basin water availability. The obtained estimates can be used to project future changes in regional water resources under changing climatic conditions.