| As one of the “three rivers and three lakes” which are the main targets ofChina’s water pollution control, Chaohu is polluted by severe eutrophication. Andthe severe eutrophication caused by the high content of nitrogen and phosphoruslead to the outbreak of blue-green algae, which results in the deterioration of water.Studies have shown that non-point source pollution has become one of the mainsources pollution of water. To get better understanding of non-point source pollutionand have the pollution controlled, domestic and foreign experts proposed modelresearch program. The research and application of non-point source pollution modelcan provide a quantitative description of the pollution within the complex process;help us to understand the characteristics of point source pollution in time and spaceand identify the main source and migration path of it; predict the load of pollutantand its influence to the water; get scientific assessment of the land-use and providedecision-making basis for the planning and management of the watershed. Soil andWater Assessment Tool Model, based on the hydrological cycle simulation, simulateand analysis the elements which take part in and influence the hydrological cyclechange process, and is a distributed model based on the watershed scale. Forresearch needs, This study focused on Wang Nan&Wang Bei dyke which is thetypical dyke area of Chaohu basin. And we also had key monitoring on Chaohusemi-Lake monitoring sections Yu Xikou and Hubing point.The content of this study include:①The study of the space distributioncharacteristics of regional agricultural non-point source pollution load and the mainfactors.②The output characteristics of the nutrients by the rainfall and drainageevents in dyke area.③The variation of pH, DO, NH3-N and CODMnof each weekin a year of the Chaohu semi-Lake monitoring sections Yuxikou and Hubing point.④The evaluation and analysis of the water quality of Chaohu Lake in2012.⑤According to the simulation results with the measured value of the degree of fit withthe credibility, to determine the applicability of the SWAT model.1) The study of the space distribution characteristics of regional agriculturalnon-point source pollution load and the main factors. The main factor of the spatialdistribution of agricultural non-point source pollution load is rainfall. The load ofeach kind of pollution in the years with high rainfall is bigger than it in years withlow rainfall. And the land-use type is an important influencing factor to agricultural non-point source pollution. In general the higher gradient the area is, the load ofagricultural non-point source pollution is worse.2) Wang Nan polder discharge water to Zhegao about172886.16m3(5186.56m3/ha), for Wang Bei polder is269010m3(8070.26m3/ha). The tendency ofthe displacement of the two polder in each month shows no difference, that is, thelargest displacement in July, less displacement in April, May, September andOctober, especially for Wang Nan polder. From April to October, Wang Nan’spollutant output (648.22kg) is lower36.59%than it in WangBei (1022.30kg). It’sbecause the relatively large displacement of the North dyke, and the nutrient outputload and the displacement are proportional relationship. It indicates that theexcessive drainage may promote the drainage of nutrient into Zhegao River.3) From January to December, Anhui Chaohu Yuxikou point bit of the ChaohuLake Basin. The month with most weeks of Grade II water is October, one week,;The month with least weeks of Grade II water is October, one week; The month withmost weeks of Grade Ⅲ water is October, two weeks; The month with least weeksof Grade Ⅲ water is April, one week. It’s the same for Hefei Hubing point.4) Overall, the pollution level of western half of the lake is significantly higherthan the eastern half of the lake. If the TN and TP are not in the evaluation, the waterquality assessment of the eastern half of the lake is class III, the western half is IV,the performance of the whole water quality is class IV. If the TN and TP are in theevaluation, t the water quality assessment of the eastern half of the lake is classⅣ~Ⅴ, the western half is class Ⅴ, the performance of the whole water quality isclass Ⅴ. Similarly, the nutritional status of the water in the lake of the western halfis worse than the eastern half of the lake.5) The simulation results of the nutrient output load of the typical smallwatershed polder shows that, the simulation result of the total nitrogen matches themeasured values of the total nitrogen well (R2wn=0.8734、R2wb=0.8619). And thecredibility is so good that the performance is applicable (Enswn=0.8436、Enswb=0.8854). However, the coincidence degree (R2wn=0.6740<0.7、Enswb=-1.25<0)between the simulated and measured values of total phosphorus is not goodenough. Maybe it is caused by the low content of phosphorus and phosphorus issensitive to the environment. So it is necessary to improve the total phosphorusanalog in this study. |
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