Soil erosion quantitative evaluation of small watershed in Loess Plateau based on AnnAGNPS model

The Annualized Agricultural Non-Point Source Pollution model(AnnAGNPS) was used to evaluate soil erosion of Zhuanyaogou watershed in the hilly area of loess Plateau in China. Results show that the relative errors of runoff and sediment yield are 10% and -10% using monitoring data of eight times runoff events, respectively. AnnAGNPS model provides reasonable estimation result of long-term annual runoff and sediment yield. AnnAGNPS model is suitable for quantitative evaluating runoff losses and soil erosion in the hilly area of Loess Plateau. Therefore, the soil erosion of small watershed was simulated based on the land use pattern in 2004 and the spatial distribution of soil erosion were analyzed. The average sheet and rill erosion intensity is 3508 t/(km²·a), which belongs to moderate erosion. Average gully erosion intensity belongs to intensive erosion, which is distinctly higher than that of other land use types. Because there is serious gully erosion, the sediment loading of watershed outlet is obviously added.