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Subject: search.filters.subject.Sediment Yield

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    STREAM FLOW AND SEDIMENT YIELD MODELING: THE CASE OF ROBI JIDA WATERSHED, UPPER BLUE NILE BASIN, ETHIOPIA
    (Hawassa University, 2024-12-24) BELSTI DEGU NURIE
    Soil erosion, streamflow, and sediment studies are crucial for supporting the agricultural sector through watershed planning and management practices. This study aimed to model stream flow and sediment yield in the Robi Jida watershed in the Upper Blue Nile Basin, Ethiopia, and identify best management scenarios with the records of suspended sediment concentration. The historical records of the meteorological, hydrological, and suspended sediment concentration data were used for the hydrological modeling. Sediment yield data was generated from the discharge-sediment rating curve equation using the suspended sediment concentration data. Spatially, 30*30 m DEM, 90*90m soil, and 30*30m resolution land use/land cover data were used as input for the hydrological model. In this study, the Soil and Water Assessment Tool (SWAT) model was used to model streamflow and sediment yield. The model performance in simulating streamflow and sediment yield was evaluated through sensitivity analysis, calibration, and validation processes. Period from 1994 to 2010 was used for calibration and 2011 to 2018 was used for validation. During calibration the model performance statics R2 , NSE, and PBIAS were obtained (0.80, 0.70), (0.80, 0.70), and (-4.8, 1.1) for stream flow and sediment yield respectively, and similarly for model validation R 2 , NSE, PBIAS as obtained (0.77, 0.72), (0.77, 0.71), (-4.7, -5.7) respectively. Therefore, the result indicated that the SWAT model performed well and the estimated average annual sediment yield of the Robi Jida watershed was 6.42 tons/ha/year. Based on the average annual simulated sediment yield, identified 9 sub-watersheds are critical whose annual sediment yield limit ranges above the tolerable limit were identified and prioritized for effective watershed management. Therefore applying and evaluating the different management scenarios, filter stripe 1m and 5m, vegetative contour strip, soil/stone bund, terracing, and contouring resulted in a 19.15%, 35.01%, 47.13%, 57.09%, 73.37%, and 52.81% decrease in the average annual sediment yield, respectively. Therefore, soil/stone bund and terracing scenarios demonstrated the highest potential for reducing sediment yield and showed promising results as effective best management practices in the Robi Jida watershed.
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    ESTIMATION OF SOIL EROSION AND SEDIMENT YIELD OF GEFFERSA RESERVOIR WATERSHED
    (Hawassa University, 2021-07-10) KANAOL MERERA ABDISA
    Sedimentation is an important parameter to measure the life of a reservoir. It depends on sediment yield and sediment yield depends on soil erosion. This study has been conducted in Geffersa reservoir watershed in the upper Awash River basin of Ethiopia. The objective of the study is to estimate potential soil erosion, sediment yield from the watershed and identify hotspot areas for proper planning using Arc GIS and RUSLE adopted to Ethiopian condition. The revised universal soil loss equation (RUSLE) was integrated with Geographic Information System (GIS) to model the spatial patterns in soil erosion in the watershed. All the parameters of the model (erosivity, erodibility, steepness, land use land cover, and supportive practice factors) were used in ArcGIS to create a soil erosion map. The annual soil loss of the watershed range from 0 to 728.48 ton/ha/year. The average annual soil loss value was found to be 23.6 ton/ha/year and has been classified into five erosion severities classes as very slight, slight, moderate, severe, and very severe to identify erosion hotspot area. Based on those results, 772.73 ha & 606.34 ha of the watershed were felt under severe and very severely vulnerable to soil erosion. The estimated Sediment yield delivered to the outlet was found ranges 0 to 78 ton/ha/year. The average annual sediment yield from the entire watershed is 5.3 ton/ha/year. If the same rate of sedimentation continues, the total storage volume will be filled up in 394 years. Out of the available reservoir sedimentation management strategies, watershed management is the best technique to minimize the sediment yield and its flow into the reservoir.