Prediction of Sediment Inflow into Dire Reservoir and Assessing Sediment Reduction Methods Using SWAT model

Abstract

Sediment inflow and sedimentation of the inflow sediment study is most important practices in the design and management of reservoirs and in water resources development. Sediment transport is a worldwide environmental problem that degrades soil productivity, water quality, causes sedimentation to the reservoirs and increases the probability of floods. Poor land use practices and improper management systems have played a significant role in causing high soil erosion rates, sediment transport and loss of reservoir storage capacity. Dire reservoir has a problem of sedimentation and erosion and Dire catchment which contribute sediment to this reservoir has a drainage area of 78 km2 . To develop effective erosion control plans and to achieve reductions in sedimentation it is important to predict the sediment yield and identify areas that are vulnerable to erosion. Soil and Water Assessment Tool (SWAT), which is computationally efficient model has been used to predict sediment yield and to test the potential of different sediment management interventions in reducing sediment yield. The model was calibrated and validated against measured flow and sediment data. Both, calibration and validation results, showed a good match between measured and simulated flow and sediment. Flow calibration gives coefficient of determination (R2 ) and Nash-Sutcliffe simulation efficiency (ENS) of 0.78 and 0.72 respectively. Flow validation gives coefficient of determination (R2 ) and Nash-Sutcliffe simulation efficiency (ENS) of 0.75 and 0.64 respectively. Sediment calibration gives (R2 ) and (ENS) of 0.9 and 0.82 respectively. Sediment validation gives (R2 ) and (ENS) of 0.66 and, 0.64 respectively. The model prediction results indicated that the total amount of sediment yield in baseline time in the Dire catchment was 48,991.8 ton/year. The model was also applied to evaluate the potential of different sediment management interventions to reduce sediment production. The investigation showed that implementing contour farming, filter strips, strip cropping on contour can reduce sediment yield by 79%, 75% and 64% respectively. Contour farming has high sediment reduction potential than other practices, so it is the best management practice that should be applied in the catchment