Modeling sediment yield of Rib watershed, Northwest Ethiopia

Application of models to assess soil erosion processes and design best management practices in Ethiopia has been increasing. This study investigated and predicted the processes and patterns of sediment yield in the watershed. SUFI-2, a SWAT CUP2012 program was applied to optimize sediment parameters using observed sediment data of the watershed. Channel erodibility factor (CH_ERODMO), exponent parameter for calculating sediment reentrained in channel sediment routing (SPEXP) from channel parameters, and USLE equation support practice factor (USLE_P) from landscape parameters have been found to be the highest sensitive sediment yield parameters. Multi-objective function statistics of R2 (0.65, 0.54), NSE (0.57, 0.51), PBIAS (1.2%, 19%), and RSR (0.66, 0.7) were identified for calibration and validation respectively. Performance measurements of P-factor and R-factor value of (57%, 39%) and (0.87, 0.48) for calibration and validation respectively were obtained. Generally, the model evaluation statistics suggested that SWAT underpredicted peak sediment loads in calibration and validation periods. According to model evaluation performance measurements, the modelled sediment yield was between ‘Satisfactory’ to ‘Very Good’ rating scales. The calibrated model provides information to apply the model in other ungauged watersheds of similar topography, land use, soil and climate for erosion assessment, and implementation of best management scenarios in Ethiopian. © 2020 Indian Society for Hydraulics.