Study Of AnnAGNPS Model In Shuang Yang Reservoir Catchment About Non-point Source Pollution

Presently, The surface water contamination caused by the nonpoint source pollution (NSP) is getting outstanding increasingly. The investigation indicates that, the NSP is the main cause, which leads to the surface water contamination, and the agricultural nonpoint source pollution (ANSP) possesses the max contribution ratio. In our country, the ANSP is also serious. The status of many water areas are unoptimistic, such as the Tai Lake in Jiangsu, the Cao Lake in Anhui, the Fuxian Lake in Yunnan, the Miyun Reservoir in Beijing, the Yuqiao Reservior in Tianjin and the Xinlicheng Reservior in Jilin. The research and control of the ANSP get starting later in our country, so that more work need to be done in the field.As the most important commodity grain production base, the Jilin province is brought the severe potential harm to its environment by plowland over-reclamation, over-fertilization and excessive crop-dusting. The Shuang Yang reservoir is one of the standby waterhead sites for Changchun that is a hydropenic city. As for Changchun, the important task of the current study is assuring the security of the domestic water supply and meeting the agricultural process water demand, so systematically investigating the water environment contamination, especially the ANSP, in the Shuang Yang reservoir watershed, is practical and meaningful.In this paper, the Shuang Yang reservoir watershed is taken as the study object. A survey is implemented to ravel the circumstantialities of the nature resources and agriculture output in the watershed. Combining qualitative and quantitative analysis, associating field investigation with indoor experiment and supported by the GIS, researches in the followed fields are carried through.1. Collecting water samples from the surface water and the groundwater around the study area, total nitrogen content and total phosphorus content are determined to assess their pollution in the area. Surface water evaluation shows that: the total nitrogen of water in and around the reservoir is badly overproof, while the total nitrogen of the surface water in the upstream area is within the standard. In most places of the study area, the phosphorus is within the standard, while the index is one time higher than the standard in water near the reservoir; groundwater assessment presents that: the total nitrogen content and total phosphorus content are dispersedly distributed in the area, several places are heavily polluted; the GIS is employed to map the distribution maps of the nitrogen and phosphorus in the water.2. By the methods, such as field investigation, testing and analysis and document retrieval etc, the parameters for the ANSP model of the Shuangyang reservovir watershed are determined. The parameters include geological information data, soil parameters, the parameters of fertilizer and pesticide, weather data, the CN of runoff curve and soil erosion factor K etc. When extract the geological information of the watershed and sub-catchment, the simulation of the Shuangyang reservoir AnnANGNPS model is executed. Fitting feedback analysis method is employed to distribute the catchment areas in the Shuangyang reservoir. The optimum grid partition level of the catchments is given, while the model reaches stabilization, and the result indicates the number of the optimum partition grid is 94.3. With the parameters determined, the AnnAGNSPS model is established, so that the estimations of the total nitrogen, the total phosphorus and the loss of sediment are gained. From the result of the simulation, we can see, during the research period (2006.5～2006.10), in the Shuangyang reservoir watershed the burden of the total nitrogen, the total phosphorus and the sediment is 341.6ton, 25.86ton and 43691.7ton respectively. As for temporal distribution, the burden of the total nitrogen, the total phosphorus and the sediment mainly concentrate in June, July and August (80% for both the total nitrogen and the total phosphorus, 74% for the sediment). It is obvious that the ANSP is closely correlative with the precipitation. When it comes to the spatial distribution, the burden of the total nitrogen, the total phosphorus and the sediment mainly concentrate in the hillslope and irrational fertilization area.4. Return the farmland with the hillslope over 25 degrees to forest, the simulation result shows the pollution burden of the total nitrogen, the total phosphorus and the sediment drops 15% respectively at least.This indicates that cultivation along the slope is important reason for the contamination runoff greatly in local area.So, returning the farmland with the hillslope has important meaning in local area.