[Evaluation of AnnAGNPS model for simulation water and sediment yield in the Lianshui River watershed]

Soil erosion has caused a series of environmental and ecological issues, such as land resource degradation and water pollution. It is an effective approach for quantitative evaluation and control of soil erosion by using processes based mathematic models. In this study, the Cell discretization units was extracted and a large number of basic geographical data including Digital Elevation Model (DEM), land use, soil as well as crop management practices, were collected and parameterized. The distributed computer modeling for water yield, sediment yield for the years 1991 to 2005 were carried out in the study area of Lianshui Basin, Xingguo County, Jiangxi province by using the basin scale AnnAGNPS model developed by USDA. The average simulation error and deterministic coefficient (R2) were 11.8% and 0.94 for annual surface flow and 19.71% and 0.77 for annual sediment yield,respectively. The simulation result indicates that the model has an acceptable performance in prediction of surface flow and sediment loading in Lianshui basin. However, the predicted subsurface flow is much less than observed value, and the reason and the applicability for subsurface flow module in Lianshui basin will be further checked up in the future study. The spatial distribution of the sediment yield in the study area was analyzed using the simulation results. The average soil erosion amount is 1150.29 t x (km2 x a)(-1), which imply that Lianshui basin belongs to slight erosion. The areas nearby residential area and along the roads were the main sources of soil erosion and the soil loss is closely related to human activities.