Study Of Non-point Source Pollution Above Fangjia Section In Yinma River Upstream Watershed

As the development and progress human society achieved, science and technology have created enormous material and spiritual wealth for mankind. The human society's material standard of living and cultural standards of living have all been significantly improved. But the development of economy has done huge harm to the environment. Water resources are always the key factors to humanity's existence and development. Especially in the current shortage stage, water pollution can be found everywhere. How to control the water pollution and how to use water more efficiently is already becoming a serious problem which needs humanity faces together.The management and controlling method in the point source pollution aspects have become mature enough. But it can not change the water pollution phenomena, because the non-point source pollutions also exist besides the point source pollution. Many developed countries have reported that even the point source pollution had been fully controlled, the water quality qualified rate reaches only 65%, and 42% of the lakes,78% of the sea areas. So the non-point source pollutions is considered as a main problem in water pollution. The assessment and solution to the non-point source pollution issues are very important.The Fangjia section in Yinma River upstream watershed is chosen for this research using a lumped parameter model called AnnAGNPS. The AnnAGNPS software is created and developed by the USDA-Natural Resource Conservation Service and USDA-Natural Resource Conservation Service in the purpose of computing and simulating the export of agricultural non-point source pollutants. It mainly contains three parts: the hydrological model,the soil erosion model and the pollutants transport model. The hydrological part bases on the SCS curve number method which is used to calculate the flow from one rainfall. The Universal Soil Erosion Equation is applied in the soil erosion model to simulate the soil erosion in the watershed. At last, the Nitrogen export and Phosphorus export are computed by the pollutants transport model. Many references are provided by the software helping the users make sure the parameters value in the procedure.At the beginning, the database should be set up carefully. The program is completed through the following steps: The contour in the watershed is drawn basing on a topographic map at the scale of 1:200000. Then the ArcGIS software change the contour to the DEM(Digital Elevation Model). The land utilization chart and Soil type chart are also produced at the same scale by the software MapGIS after detailed investigation. Basing on the actual situation of in the area, appropriate meteorological elements and soil characters like the CN value and soil erosion factor K etc, crops characters, and other parameters are valuated carefully to prepare for calculating process. At the end, all the prepared data is put in the AnnAGNPS Input Editor 3.51.Single rainfall events are used to revise the AnnAGNPS model as well as improve the precision. The critical areas in each pollutant materials are identified in the output charts. Then the key sensitive parameters are analyzed and compared in the following chapter.As a result, the conclutions are drawn as below:1. The caculating result of the model:The total amount of sediment erosion of the Yinma Upstream Watershed between June and September in 2006 is 426317.6t, the average erosion modulus is 198.6t/hm2; the total nitrogen export is 423.4t, incluses 309.6t desolved nitrogen and 113.8t attached nitrogen; the total phosphorus export is 63.8t, incluses 23.2t desolved phophorus and 40.6t attached phophorus. 2. Critical areas identification:The critical areas is shown in the charts, north of Sijia town, south of Wanchang town, north of Shanhe town and central in Huangyu town are considered as critical area of sediment erosion. The total area is 317.6 km~2, about 14.8 percent of the whole research area bu the sediment has reached 5.1t in a hectare, the peak value is 7.9t/hm~2. The total amount is 162320t, which charges 38% of the total export of sediment.Most of Changling town, north of Shanhe town and west of Jinjia town are the critical area in nitrogen export load. Average export value has reached 2.7kg/hm~2, the total amount of nitrogen export is 174.6t, which charges 41.1% of the total nitrogen export.South of Wanchang town, north of Changling town, central of Jinjia town and central of Shanhe town are the critical area in phophorus export load. The average export value is 0.38kg/hm2, the total amount of phophorus is 13.8t, which charges 21.6% of the total phophorus export.3. The key sensitive parameters analyzition:All the three chosed parameters have big effect on the caculation result form the model.The order is the slope parameter F, the SCS curve number CN, the manning's'n'.The sediment transportion chages more than nitrogen export, and the phosphorus exportis the last one.In this foundation top, the proposed controlling approaches of sources of pollutants and runoff control measures for the management in Yinma River Upstream Watershed and the protection policy which is a service and security to control the non-point source pollution are put forward. Finally, in response to deficiencies in the simulation process, several improvements are made to the views and suggestions.