Sedimentation Modeling for Ribb Dam

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Addis Ababa University


The soil and water assessment tool (SWAT) is tested for the prediction of sediment yield in Ribb River watershed. Poor land use practices and improper management systems have played a significant role in causing high soil erosion rates, sediment transport and loss of agricultural nutrients. In this research a physically based watershed model, AVSWATX is applied to the Upper Ribb River watershed for modelling of the hydrology and sediment yield. The main objective of this study is to predict the sediment yield to Ribb dam reservoir. The model is calibrated and validated taking the Upper Ribb gauging station near Debretabor. 20 years daily metrological, flow and sediment rating curve equation for sediment data BCEOM (1999) are used for model calibration and validation. The model is calibrated and validated for both flow and sediment concentration at upper Ribb (844km2) and run at Ribb dam reservoir outlet (686km2) to estimate the sediment yield. Flow calibration gives coefficient of determination (R2) and Nash-Sutcliffe simulation efficiency (ENS) 0.817 and 0.812 respectively. Flow validation gives 0.817 and 0.8 for R2 and ENS values respectively. Sediment calibration gives R2 and ENS 0.78 and 0.59 respectively and validation test gives R2 and ENS 0.54 and 0.52 respectively. This result indicates that the observed values show good agreement with simulated value for both flow and sediment yield. In this study the SWAT model yields average annual sediment of 72.79 ton/km2 (7279 ton/ha) at Ribb dam site. This result is similar with research done by BCEOM (1999) which is 82 ton/km2/y. The calibrated model can be used for further analysis of the effect of climate and land use change as well as other different management scenarios on stream flows and soil erosion. The result of the study could help different stakeholders to plan and implement appropriate soil and water conservation strategies. Key words SWAT,Map,DEM,sedimentation,Ribbdam,Watershed,Digitizing,simulation,calibration validation.



SWAT;Map;DEM;Sedimentation;Ribbdam;Watershed;Digitizing;Simulation;Calibration Validation.