Himalayan regions have increasing sediment yield due to undulating topography, slope and improper watershed management. However, due to limited observation data, and site accessibility issues, less studies have quantified sedimentation loads in the Himalayas, especially Nepal. This has hindered the investments on run-of-river hydropower projects as high and unpredicted sedimentation has increased losses in hydropower production. Therefore, there is a need to understand key physical processes driving sedimentation in these regions, with the available data. This study used the Soil and Water Assessment Tool (SWAT) to estimate the sedimentation yields in the Kaligandaki basin of Nepal, which is an important tributary that drains into the Ganges. Multi-source data from field observations, remote sensing platforms, surveys and government records were used to set up and run the SWAT model for the Kaligandaki basin from 2000 to 2009. Results for the 10-year model run indicate that 73% of the total sediment load is estimated to come from the upstream regions (also known as High Himalayan region), while only 27% is contributed from the Middle and High Mountain regions (where land management-based interventions were deemed most feasible for future scenarios). The average sediment concentration was 1986 mg/kg (ppm), with values of 8432 and 12 mg/kg (ppm) for maximum and minimum, respectively. Such high sedimentation rates can impact river ecosystems (due to siltation), ecosystem services and hydropower generation. In addition, model results indicate the need for better high frequency observation data. Results from this study can aid in better watershed management, which is aimed at reducing sedimentation load and protecting Himalayan rivers.

中文翻译：

---

喜马拉雅河流域泥沙负荷的估算：以尼泊尔的加里甘达基为例

由于地形起伏，坡度和流域管理不当，喜马拉雅地区的沉积物产量不断增加。然而，由于观测数据有限，以及场地可及性问题，较少的研究对喜马拉雅山特别是尼泊尔的沉积负荷进行了量化。由于过高的和不可预测的泥沙增加了水电生产的损失，这阻碍了对流域水电项目的投资。因此，需要利用可用数据来了解驱动这些地区沉积的关键物理过程。这项研究使用土壤和水评估工具（SWAT）估算了尼泊尔Kaligandaki盆地的沉积物产量，尼泊尔是流向恒河的重要支流。来自野外观测，遥感平台，调查和政府记录用于建立和运行2000年至2009年Kaligandaki盆地的SWAT模型。10年模型运行的结果表明，估计总沉积物负荷的73％来自上游地区（也包括被称为喜马拉雅山高地区），而只有27％的资金来自中部和高山地区（在这些地区，基于土地管理的干预措施被认为对未来情况最可行）。平均沉积物浓度为1986 mg / kg（ppm），最大值和最小值分别为8432和12 mg / kg（ppm）。如此高的沉积率会影响河流生态系统（由于淤积），生态系统服务和水力发电。此外，模型结果表明需要更好的高频观测数据。这项研究的结果有助于改善分水岭的管理，