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Firstly, the Yangtze River in 1990-2000 agricultural district level statistics, over the same period TM images acquired on the basis of vector data, academic journals and published literature relevant data and converting IPCC published data and other basic data source , in the establishment of the agricultural area nitrogen balance change model based on GIS technology as a means to calculate the Yangtze River counties from 1990 to 2000, changes in nitrogen balance, and then summarizes the whole basin of nitrogen input, output, and the remaining amount . The results show that the whole basin agricultural area 1990 N input capacity of 7.65 × 10 ~ 6t / a, output was 4.23 × 10 ~ 6t / a, the remaining amount of 3.42 × 10 ~ 6t / a, which enters the water content of 2.05 × 10 ~ 6t / a, the amount of residue in the soil 1.37 × 10 ~ 6t / a; to 2000 basin-wide agricultural area of N inputs is 10.22 × 10 ~ 6t / a, output was 5.44 × 10 ~ 6t / a, the remaining amount of 4.78 × 10 ~ 6t / a, where the amount of the water into the 2.65 × 10 ~ 6t / a, the amount of remaining in the soil 2.13 × 10 ~ 6t / a. 1990 to 2000 Yangtze River Basin agricultural area of nitrogen input variation is 2.57 × 10 ~ 6t / a, nitrogen output variation of 1.21 × 10 ~ 6t / a, the remaining amount of variation 1.36 × 10 ~ 6t / a, which enters water bodies nitrogen change amount is 0.60 × 10 ~ 6t / a, the nitrogen remaining in the soil change amount is 0.76 × 10 ~ 6t / a. Research Yangtze River nitrogen balance changes as well as water pollution impact analysis results mainly due to chemical fertilizer nitrogen input change, Chongqing, Shanghai, Wuhan, Wuxi, Nanchang, Tanghe, Newfield, Yangyang, Chengdu, Suining area of nitrogen into the water volume larger changes, agricultural areas for the Yangtze River Water Pollution Prevention and Control Regionalization of nitrogen. In order to effectively combat the Yangtze River Agricultural Non-point source nitrogen pollution, best management practices can be taken from the source and reduce agricultural non-point source runoff of nitrogen generation; and also with the appropriate education, regulatory, technical, economic and other means ensure that agricultural non-point source nitrogen pollution has been effectively controlled. Secondly, the Three Gorges reservoir area in 2001-2005 at district level agricultural statistics, vector, combined with the above methods, analytical results Three Gorges reservoir area in recent years (2001, 2003 and 2005) the nitrogen load and agricultural area of Three Gorges Reservoir water body nitrogen pollution control in key areas: Changshou District, Shizhu, Wulong County, Jiangjin, Fengdu County, Badong County, Yichang County, Xingshan County and Banan District. Finally, the use of a small river upstream of the Three Gorges Reservoir East River Basin January 1, 2003 to December 31, 2004 daily meteorological data, land use type, soil type, DEM data, through nutrient SWAT model simulation results East River watershed unit area in July, September NO3 larger surface erosion; 4,7,8,9 month organic N load is large. After further verification and calibration parameters, SWAT model can be extended to the Three Gorges reservoir area or even the entire Yangtze River basin.
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