Modeling Sediment Yield Using Arcswat And Analyzing The Most Prominent Remedial Measures: Cases of Melka Wakena Reservoir, Ethiopia

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Addis Ababa University


Sediment accumulation in a reservoir is a serious problem that threatens sustainability of the reservoir and has severe consequence on reservoir productivity during its operation time. Therefore, this study was initiated to model sediment inflow and to suggest mitigation measures for Melka Wakena reservoir which is located in the highlands of Arsi Zonal Administration of Wabi Shebele river basin about 280 km south east of Addis Ababa. The ArcGIS interface Soil and Water Assessment Tool (ArcSWAT) was used to model the soil erosion in the watershed. The input data were Metrological, Hydrological, land use/land cover map and soil map which were collected from concerned government offices. The result showed that statistical model performance measures of the coefficient of determination (r2) of 0.894, the Nash–Sutcliffe simulation efficiency (ENS) of 0.862 and percent difference (D) of 0.31, for calibration and 0.825, 0.77 and -0.011, respectively for validation, indicated good performance of the model simulation of Sediment load from the watershed on yearly time step. The model result showed that 1637.2 tons/Km2/year of sediment load have been flowing to the reservoir from the watershed. This indicates 0.63% of a total storage capacity lost per year. The annual economic loss due to reservoir sedimentation is 2.36 million birr. Subbasin 3, 2, 11 and 9 ranks first to fourth according to their Sediment yield respectively and found as critical subbasins. Soil and Water conservation program at critical subbasins with vegetation screens upstream of reservoir was found the best and feasible option to reduce sediment inflow into the reservoir. Key Words Melka Wakena Reservoir, Reservoir Sedimentation, ArcSWAT, DEM, Calibration, Validation



Melka Wakena Reservoir, Reservoir Sedimentation, ArcSWAT, DEM, Calibration, Validation