Application Of Swat Model In Non-Point Soure Pollution Simulation Of Mang Xi Watershade

With the point pollution source is gradually managed and controlled, non-point pollution source has become the primary induced factors of the water environment deterioration and lake eutrophication. Mangxi River, which is the major water source for industrial and agriculture, flows through Yan town. Mangxi Rivers plays an essential part in social-economic development of Yan town. With the fast development of the economy, the water quality of Mangxi River is decreasing with the intense of eutrophication, which have bad impacts on water safety. Because of this, this work adapts SWAT model, which is developed by the U.S. Department of Agriculture, to build a non-point source pollution model suits Mangxi Watershed. The author hopes this work could provide a scientific basis and effective ways to manage water environment. The following are main content of the work and major outcomes:(1) The SWAT model simulated show that the output amount of nitrogen of non-point pollution is biger than that of point pollution, so the main form of pollution in Mangxi Watershed is non-point pollution.(2) By using the SWAT model to do a spatial analysis on Mangxi Watershed basin sediment and nutrient load. The result show that the east part of Mangxi Watershed has greater sediment, nitrogen and phosphorous load than the west part; in terms of pollutants, the sediment load is mainly distributed in the east part of Mangxi Watershed; the nitrogen and phosphorous load are mainly distributed in the downstream area of Mangxi Watershed. Those are related to the land-use, land type, gradient, and human activities.(3) The results of SWAT model show that within the study area, the sediment and nutrient output have a strong time rule. Organic nitrogen and organic phosphorous output peak during the rainy season (May-September) so that the rainy season is the main period of non-point source pollution output. There is a strong relationship between the output of nutrient and the runoff.(4) The study find five cases by changing the input data of nitrogen fertilizer,and simulates under the cases.The results show that reducing the amount of chemical fertilizer can significantly reduce non-point source pollution in the study area, and the of nitrogen is greater than that of organic nitrogen.So in order to reducing the non-point pollution,the controlling fertilizer should be considered first, and other agriculture management also needed.