Assessment on Surface Water Potential and Demands of Wabishebele Basin in Ethiopia

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Addis Ababa University


Water is, like the air we breathe, a basic requirement for all life on Earth. It is vital for many aspects of economic and social development, e.g., for energy production, agriculture, domestic and industrial water supply, and it is a critical component of the global environment. There is growing awareness that development, including development of water resources, must be sustainable, which implies that the world’s natural resources must be managed and conserved in such a way as to meet the needs of present and future generations. An output of this study is readily available to assist planners and managers to make decision on water resource availability in a catchment and also is to assess and forecast water demand in the basin. The soil and water assessment tool (SWAT) and water evaluation and planning system (WEAP) were used for the prediction of surface water potential and demands of Wabishebele River basin respectively. The objective of this study is to quantify the surface water resources within the basin and assessing the demands in the basin using rainfall-run-off and water resource modeling. The model was successfully calibrated and validated for measured stream flow at Gode gauging station. Flow calibration gives coefficient of determination (R2) and Nash-Sutcliffe simulation efficiency (ENS) 0.70 and 0.82 respectively. Flow validation gives 0.70 and 0.87 for R2 and ENS values respectively. The calibration and validation result showed that model performance evaluation statistics (coefficient of determination (R2) and Nash-Sutcliffe model efficiency (ENS)) were in the acceptable range. The demand was computed based on three (3) scenarios – Scenario 1: Irrigation projection, Scenario 2: Dam construction and Scenario 3: Increase water demand scenario. The study found that the catchment is relatively sensitive to the Increase water demand scenario and Irrigation projection, suggesting that the slight changes will alter the present and future water availability. Results indicate a general trend of declining water supply and increasing unmet demand in the basin. In this study the SWAT model yields average annual run off of 3.76B m3at Gode and an annual demand of 512.6Mm3 (2000) , 3615.52Mm3 (2030). Keywords: Water Evaluation and Planning, SWAT, Water Demand, surface water, Wabishebele Basin, calibration validation.



Water Evaluation and Planning, SWAT, Water Demand, Surface water, Wabishebele Basin, Calibration validation