OPTIMAL WATER ALLOCATION AND WATER DEMAND ASSESSMENT: CASE STUDY BARO WATERSHED

Abstract

Watershed is considered to be the ideal unit for management of the natural resources. Extraction of watershed parameters using (GIS) and use of mathematical models is the current trend for hydrologic evaluation of watersheds. The aim of this thesis is to oversee the effect future water resource development projects on the Baro watershed using SWAT models to assess water availability and WEAP mo dels in assess the water demand of the study area. The SWAT model was calibrated and validated for measured stream flow at Baro near Gambela gauging stations. The calibration and validation result showed that model performance evaluation statistics (coefficient of determination (R 2 ) and Nash-Sutcliffe model efficiency (ENS)) were in the acceptable range (R 2 =0.76 ,E NS =0.72 for calibration and R 2 =0.7,E NS=0.63 for validation). This indicates that the observed values show good agreement with simulated flow value. In this study the watershed yields average annual surface runoff of 425.07 mm. Using WEAP, this study investigated the trend of supply and demand in Baro catchment . The assessment model is computed based on two scenarios, Scenario1: Irrigation project development and Scenario 2: Extended Dry Climate condition, in order to see how Baro watershed responds to the supply of water resources. Based on the result, there will be unmet demand in the years (2033-2034 and 2044-2045 for scenario 1) and (2033-2050 for scenario 2). The study area tends to experience more water scarce problem in the second scenario; ―Extended dry climate sequence‖ starting from the year 2033. there for a better water resource management should perform to overcome this shortage.