Asian Journal of Research in Agriculture and Forestry

Ethiopia’s main issues are the degradation of land and water resources. SWAT2012, a physically based watershed model, was used to this work to analyze runoff and sediment yield analysis in the Ariqua watershed. Estimating the runoff, analyzing the sediment yield, and prioritize the most erodible sub- watersheds were the main objectives of this research. A 30 x 30 m DEM (Digital Elevation Model), a soil map, and a land use map were utilized to set up the model for simulation. The daily recorded weather data from 1991 to 2015 were used as input to the model. For the SWAT simulation, daily stream flow and sediment data from 2001 to 2015 were used. Both automated and manual calibration methods were used to calibrate the model. Calibration took place throughout the frist sixyears (2006-2011), where as validation was place during the remaining years (2012-2015). To assess the model’s performance, sensitivity analysis, model calibration, and validation were also carried out. Thirteen sensitive parameters were identified for flow of which runoff curve number for SCS moisture condition (CN2) was the most sensitive one and ten sensitive parameters were identified for sediment of which soil erodibility factor (USLE_K) was the most sensitive. Model calibration and validation were assessed using Nash Sutcliffe (ENS) and the coefficient of determination (R²). Both showed a good model performance agreement (model of fitness) between the simulated and measured monthly flow and sediment yield. The 15-years average observed and simulated stream flow created according the model prediction result, was 137 m³/s and 124 m³/s, respectively, while the sediment yield was 12.54 ton/ha/yr and 13.92 ton/ha/yr. Sub-watersheds (SWT-23) and (SWT-20) produced high stream flow rates of 383.5 m³/s and 287.3 m³/s, respectively, out of the 23 sub-watersheds.