Climate Change Impact on Water Resources Availability of Finchaa-AmertiNeshe Multipurpose Cascaded Reservoirs

Abstract

The most profound effect of climatic change may be alterations in the regional hydrologic cycle and changes in regional water availability. Besides the increasing water scarcity, climate change threatens to exacerbate the current supply-demand imbalance. In this study, the impact of climate change on water availability and reliability to satisfy the increasing demand under changing the climate on Finchaa sub-basin has been evaluated using the Water Evaluation and Planning
(WEAP) model. WEAP package was utilized to simulate the future water availability using the runoff generated by the Hydrologiska Byråns Vattenbalansavdelning (HBV) model as an input. The performance of the model was assessed using statistical tools such as Nash and Sutcliffe efficiency criteria (R2) and the Relative Volume Error (RVE) during model calibration and validation steps. R2 values were greater than 0.8 and RVE values were near 0 for all the three sub-catchments showing the better performance of the model. The prediction for future climate variables, on the other hand, showed an increasing trend for both maximum and minimum temperature values. However, for precipitation, it doesn’t manifest any systematic increasing or decreasing trend in the next three decades. Consequently, the total water availability in the study area is expected to decrease by 11.88% in the next thirty years. Compared to the base scenario, the simulated future inflow to Finchaa and Neshe reservoirs has shown a slight increment at the end of 2025 and a small decrease at the end of 2040. However, the simulated future inflow volume to Amerti reservoir has shown a likelihood of small and considerable decrease at the end of 2025 and 2040, respectively. Considering the future expansion in the study area, all future and existing demand sites in the study area may be fully satisfied with 100% demand site coverage
and 98.89% demand site reliability under changing the climate. Finally, it can be concluded that even though the demand in the sub-basin is increasing greatly, the available water resources is expected to be satisfactory under changing climate conditions for the next thirty years.