An Application Study Of AnnAGNPS Model On Returning Land For Farming To Forestry Of Tumenxigou Watershed

With the rapid development of economy ,the pollution of small watershed became more and more serious ,and it is an urgent need to carry out remediation work. This paper researched Tumenxigou watershed ,which is five kilometer from the upper reaches of Miyun Reservior. The present pollution condition and the pollution condition of different returing land for farming to forestry was also simulated by the AnnAGNPS model in this paper. Through the simulated result , find the CSA ,the influence factor ,and the treatment of non-point source pollution.AnnAGNPS is a continuous simulation, watershed scale computer model for use in evaluating agricultural non-point source pollution. It can simulate quantities of runoff, sediment, nutrients, and pesticide yield on a daily, monthly, or yearly basis according to user's specification. Tumenxigou watershed is selected to validate the model, which in the upper reaches of Miyun Reservior. The runoff amount and the distribution of nitrogen and phosphorus output was simulated by AnnAGNPS model. The study selected ten rain events examine the runoff of model, and two rain events examine the distribution of nitrogen and phosphorus output. According the actual condition of Tumenxigou watershed, the operation parameter was confirmed, and the pollution condition was simulated. Then considering topographical factor and not considering the topographical factor, adjusted the proportion of forestry, cropland and orchard cropland, simulated the distribution of nitrogen and phosphorus output.The simulate result shows that the proportion is the higher for cropland and orchard cropland , the non-point source output is larger in watershed. Forestry can control the non-point source pollution, the larger proportion of forestry is, the less non-point source pollution is. The topographical factor influences the non-point source pollution, considering the topographical factor, the non-point source pollution output is less than the output of not considering the topographical factor..