This study aimed to assess the sediment yield in the Budhi Gandaki Basin using various methods, including empirical, statistical, and process-based models. The Budhi Gandaki Basin is a significant watershed in Nepal that plays a crucial role in providing water resources for agriculture and hydropower. However, sedimentation is a major problem in this basin, reducing the water storage capacity of reservoirs and negatively affecting water quality. The Soil and Water Assessment Tool (SWAT) model was utilized in this research to determine sediment yield in the Budhi Gandaki Basin. Given the complex sediment transport processes in steep Himalayan basins, the sediment simulations should be interpreted as indicative patterns rather than precise quantitative predictions. To our knowledge, this study represents the first application of the SWAT model for sediment yield assessment in the Budhi Gandaki Basin. The Budhi Gandaki Basin, with a total catchment area of 496,713.78 ha, was subdivided into 25 sub-basins for SWAT modeling to capture spatial variability while ensuring computational efficiency. The model is conceptual, distributed, and continuous-time, and was used to identify erosion-prone zones within the basin. Land use and soil maps were used to configure the model, which was then fed with daily temperature and precipitation data from 2001 to 2022. The study utilized daily streamflow data from 2007 to 2019 and daily sediment records from 2003 to 2014. The model was manually calibrated and validated using the observed flow and sediment data. The model consisted of 95 Hydrological Response Units (HRUs) and 25 sub-basins. It demonstrated strong performance in flow simulation, with calibration results of R² = 0.8 and NSE = 0.76, and validation results of R² = 0.77 and NSE = 0.63. However, sediment simulation performance was lower, with calibration metrics of R² = 0.61 and NSE = 0.27, and validation metrics of R² = 0.36 and NSE = 0.24. The average sediment yield was 313.89 t/km²/yr, with peak yields of 1384.66 t/km²/yr, highlighting the model’s utility for understanding sedimentation processes and informing watershed management strategies.
Adhikari et al. (Sat,) studied this question.