Investigating the climate change effects on annual average streamflows in the Euphrates-Tigris basin using the climate elasticity method

Abstract

This study was conducted to investigate the response of streamflows (Q) to changes in precipitation (P), potential evapotranspiration (Ep) and drought index within the Euphrates-Tigris basin. For this purpose, 37 sub-basins that are not affected by dams were identified within the basin. Here, the sensitivity of annual average streamflows to precipitation, Ep and drought index was evaluated by the climate elasticity method proposed by Schaake [1]. With this method, the average values of the precipitation and Ep sensitivity coefficients of the streamflow (εP and εEp, respectively) throughout the basin were calculated as 1.50 and -0.50, respectively. Therefore, it is observed that a 10% increase (decrease) in precipitation would lead to an average increase (decrease) of 15% in streamflow, on the other hand, a 10% increase (decrease) in Ep would result in an average decrease (increase) of 5% in streamflow across the basin. Moreover, the average value of sensitivity coefficient of streamflow to drought index (εØ) was determined as -0.47, which means that a 10% increase in the drought index will result in an average decrease of 4.7% in streamflow within the basin. Additionally, it is observed that there is a nonlinear inverse correlation between the climate change sensitivity coefficients (i.e., εP, ǀεEpǀ and ǀεØǀ) and the flow coefficient (Q/P) values of the sub-basins indicating that the decrease in streamflow would increase the sensitivity of streamflow to climatic changes. Finally, it was determined that there exist relative increases in εP, ǀεEpǀ and ǀεØǀ values from high to low elevations across the basin.