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Agricultural non-point source pollution to become one of the important reasons of water pollution, the environmental problems of the global scope of attention. Non-point source pollution monitoring difficult, quantitative analysis is difficult, based on mathematical models of computer simulation method in solving these problems than other non-point source pollution research methods. AnnAGNPS other large continuous distributed model becomes non-point source pollution load estimates, identify key source pollution, research an important means of agricultural management practices. Three Gorges reservoir area of ??agricultural non-point source pollution is worsening, and complex terrain, land fragmentation, agricultural operations scattered tillage diverse, field monitoring and artificial rainfall and other research methods are difficult to meet the region's agricultural nonpoint source pollution research needs, math watershed model simulations for the quantitative evaluation of non-point source pollution load provides an effective means. AnnAGNPS model is rarely applied in the Three Gorges reservoir area and more concentrated in a very small basin-wide study, the lack of a typical representative, the paper selected from the Three Gorges Reservoir Area of ??Three Gorges Dam 247km a small tributary of the river basin as the research object, using the model to establish a database AnnAGNPS : analysis of the sensitivity of the input parameters watershed; simulation Xiaojiang watershed runoff, sediment, nitrogen and phosphorus pollution load; identify non-point source pollution critical source areas; simulate three kinds of agricultural best management practices (BPMs) on watershed runoff, amount of sediment, nitrogen, phosphorus load influence in the region as a model point source pollution control study provides reference, the main conclusions are as follows: (a) small river valley in the Three Gorges Reservoir AnnAGNPS model parameters for analysis, master build AnAGNPS model required meteorology, topography, land use, soil, crops, non-crop, crop management, fertilization, pesticides, runoff curve parameters. (2) through a sensitivity analysis to determine the impact watershed non-point source pollution load output of eight major factors, including the SCS curve values ??CN, soil erodibility factor K, soil and water conservation factor P, crop management factor C, slope S, slope length L, Manning roughness coefficient MA and chemical fertilizer PERT. Runoff, sediment, total nitrogen, total phosphorus pollution load on the eight input parameter changes in response to different degrees. (3) the use of the Three Gorges Reservoir Area AnnAGNPS model 2002-2004 Xiaojiang watershed runoff, sediment yield, nitrogen and phosphorus load simulation estimates and hydrological stations were used pagoda nest (control range accounted for 62% of the basin area) 2002 2004 measured data on runoff and sediment analog values ??for calibration and validation, using a small river basin Yamaguchi 2002-2004 annual average data measured total nitrogen, total phosphorus load simulation calibration and validation. Simulation results show that the model results are relatively reliable, suitable for Three Gorges Reservoir watershed non-point source pollution load evaluation. (4) According to the model predictions, the model for runoff simulation accuracy is higher than the output of sediment and nutrient analog ,2002-2008 annual Xiaojiang watershed runoff simulation is 3.063 billion m3, sediment transport capacity of 2,778,100 t total nitrogen load 7949.38t, total phosphorus load 463.74t. Sediment and nutrient outputs have similar regularity, showed a seasonal variation, with rainfall showed a significant positive correlation, and are subject to fertilization, surface conditions and farming conditions and other effects. (5) from the spatial point of view, non-point source pollution load in the uneven spatial distribution of different types of pollution load to vary greatly. Load per unit area in the order of the waters, construction land, farmland, woodland, grassland, the total load size were followed farmland, forest land, construction land, waters and meadows. (6) from the model simulation results can be seen, the basin produces nitrogen and phosphorus load is the major source of soil erosion and fertilizer losses caused by agricultural non-point source pollution, the land use is mainly dry slope, therefore, to strengthen dry slope agricultural non-point source pollution control non-point source pollution control drainage is essential. Three different agricultural management practices through simulation studies show, forest and conservation tillage and other measures on a clear watershed pollution load reduction effect.
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