Estimation of Sediment Yield Using SWAT Model and Reduction Methods (A Case Study of the Middle Awash Multipurpose Dam, Awash River Basin, Ethiopia)
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Date
2024-02
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Addis Ababa University
Abstract
Sedimentation has been one of the critical challenges to create and sustain development opportunities for the poor families in Awash River Basin. Therefore, evaluating and understanding watershed sediment yield is vital to manage sediment related problems. Thus, this study used Middle Awash Multi-Purpose Dam (MAMD) catchment area to estimate sediment yield, to hotspot the most erodible sub-catchment area and assess the appropriate mitigation measurements to reduce the sediment load from the catchment. For the simulation of runoff and sediment yield from the MAMD watershed, the Soil and Water Assessment Tool (SWAT) model was applied. The total watershed has an area of 21,103.16 Km2 and located in Afar Regional State and Oromiya Regional State, Awash River Basin, Ethiopia. The SWAT model is calibrated and validated using SWAT-CUP with uncertainty analysis SUFI-2 (Sequential Uncertainty Fitting) procedure using measured monthly flow and sediment data from Awash and Metehara Gauge Stations. Using a data from 1993 to 2006 for calibration and 2007 to 2013 for validation, both results showed a good match between the measured and simulated flow and sediment. Flow calibration gives a coefficient of determination (R2) and Nash-Stucliffe simulation coefficient (NS) of 0.67 and 0.62 respectively. Flow validation gives R2 and NS of 0.65 and 0.63 respectively. Sediment calibration gives R2 and NS of 0.67 and 0.62 respectively. Sediment validation also gives R2 and NS of 0.69 and 0.69 respectively. Thus, the model performed well in simulating the flow and sediment for the study area. The estimated sediment result shows that the average annual sediment load at the outlet of the watershed was 40.32 ton/year. In this study, sub-basin 14 sub-basins were found to be a sediment prone areas having an annual sediment load that varies from 10.01 to 169.94ton/ha/year. Also, the model was applied to examine the Best Practice Management (BMP) scenario under the change of 25%, 35% and 50% Agricultural land use type to forest land, and other recommended scenarios to reduce the production of sediment. The investigation showed that the conversion of 25%, 35% and 50% of Agricultural land to forest land can reduce the total sediment yield by 26.59%, 34.15% and 45.76%, respectively. The implementation of Filter Strips, Grassed Waterways, Terracing, and Contouring can reduce the mean annual sediment yield at the outlet by 67.19%, 81.80%, 84.30% and 59.25%, respectively. The application of Terracing has high sediment reduction potential than other best management practices.
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Middle Awash Multi-Purpose Dam, Sediment Yield, SWAT, SWAT-CUP, BMP