ASSESSMENT OF SURFACE WATER POTENTIAL TO SELECT POTENTIAL SITES FOR HYDROPOWER IN MEGECHA WATERSHED, OMO-GIBE BASIN, ETHIOPIA

Abstract

Assessing the surface water potential available in a catchment or watershed is essential for proposing different water resource projects like hydropower and irrigation in the area. This study presents the assessment of the surface water potential in the Megecha watershed to simulate streamflows in the watershed and select potential sites and estimate the hydropower potential of the river. The watershed is located in the northeastern part of the Omo-Gibe basin in Ethiopia, stretching an area of about 1176Km2. The surface water potential of the watershed is assessed by using the ArcSWAT hydrologic model and historical hydro-meteorological data from 1988 to 2019. The ArcSWAT hydrologic model estimates the surface water potential of the study area in the forms of mean annual rainfall, actual evapotranspiration, and annual surface runoff. The model is also calibrated and validated using the observed streamflow data of 17 years from 1990 to 2006 from the gauged station near Gubrie. For model calibration 10 years, and for model validation, 7 years of data are used and indicated an acceptable model performance range. The mean monthly streamflows for ungauged and identified sites are simulated by manual calibration of an ArcSWAT model using the watershed’s sensitive parameters. After the simulation of the streamflows, the minimum available flows of the river at the selected sites throughout the year are also computed by using the flow duration curve, these minimum available flows are used to determine the power potential of the river at the identified sites in the watershed. The available gross head to generate the power potential in the watershed is computed using the topographic map of the watershed by DEM-map or GIS-based method. Corresponding to the computed available heads and minimum flows at the identified sites, the hydropower potential that can be generated from the streamflow is also estimated. For the selection of the best potential site, the multi-criteria decision-making (MCDM) analysis is applied to select the best alternative site from the identified alternatives. Therefore this can be suggested to select a better potential site for the power generation in the Megecha watershed