Framework for reservoir sedimentation estimation using the hydrological model and campaign—A case study of A Vuong reservoir in central Vietnam

Sediment estimation would help practice sustainable watershed management and efficient reservoir operation. Different methods exist to estimate reservoir sedimentation based on the differences in sediment yield flowing in and releasing from the reservoir and successive bathymetric field measurements. This paper investigates the variability in sediment yield from watersheds and sedimentation in the A Vuong reservoir in central Vietnam using the soil and water assessment tool (SWAT) compared with bathymetry mapping. Bathymetry data were collected in 2003, 2015, and 2021 and conducted in 2022. SWAT was calibrated from 1996 to 2008 and validated from 2009 to 2020 using monthly observations. SWAT performs well and can accurately simulate monthly streamflow and sediment yield. The goodness-of-fit analyses suggested that the area list representation of the watershed behavior and satisfactory Sutcliffe efficiency (NSE = 0.86) values for streamflow were obtained during the calibration and validation periods. For sediment simulation, the efficiency is lower than streamflow's, with NSE in the validation values of 0.61. The results showed that the sedimentation estimate from the SWAT model is smaller than that from bathymetry. A Vuong reservoir's annual storage capacity loss due to sedimentation accumulation from the SWAT model and bathymetry was 0.08% and 0.38%, respectively. Based on the bathymetry data, we estimated that the average rate of sedimentation deposition of A Vuong reservoir was 1.3 Mm 3 /y. The average calculated net deposition value was 4.3 m (0.3 m per year) within fourteen years of operation. The study outcomes demonstrated that the framework approach may transfer to an ungauged catchment and address the complex sedimentation problem in tropical regions.