Comparison of the Sediment Yield Estimation Using Bathymetric Survey and Modified Universal Soil Loss Equation at Shumburit Reservoir, East Gojjam Zone Amhara Region, Ethiopia
Sediment accumulation is a major factor in reducing irrigation reservoir useful life as well as reducing the reservoir capacity. Therefore, the goal of this study was to estimate the volume of sediment accumulated in the reservoir using a bathymetric survey and to assess the watershed sediment yield to reservoirs using the Modified Universal Soil Loss Equation (MUSLE) model. The bathymetric survey method involves subtracting the two-period capacities, one before dam construction and one after
... m construction. On the other hand, the sediment deposition calculated by the MUSLE model over the last six years is estimated after determining the physical parameters (K, LS, C, and P factors) and runoff index (VQ and QP) from the watershed using ArcGIS 10.8 and Excel software. The bathymetric survey showed that 297,000m3 (362,340 tons) of sediment had accumulated in the reservoir over six years of operation, whereas the Modified Universal Soil Loss Equation estimated 256,262.86 tons of sediment yield at the outlet of the watershed (inflow to the reservoir). This means the reservoir's total capacity has been reduced by 7.52 percent and 5.4 percent, respectively, over the last six years of operation, using a bathymetric survey and the Modified Universal Soil Loss Equation. According to the bathymetric survey results, the reservoir will not be functional for more than 15 years if the sediment rate remains the same as in the previous six years. Using the bathymetry method, the sedimentation rates of the dead storage and live storage zones were 31,666.67 m3/year and 48,333.33 m3/year, respectively. The watershed's sediment yield and specific sediment yield were determined using bathymetry survey results to be 61,371.95 tons/year and 45.46 tons/ha/year, respectively; whereas the sediment yield using the MUSLE model was 31.64 tons/ha/year.