| In China, water resource distribution is unbalanced, and the shortage of water in many north cities is serious. With the development of society, the demand of the water has been increasing. The surface water is one of the important parts of water resources, but it faces a challenge of significant eutrophication problems because of the excessive input of nutrient recently. To obtain the information of the input quantity of the pollutant is the foundation to make the control strategy.The MiYun Reservoir is the important surface water source of Beijing. It is necessary to master the source and the gross of nutrition that enters the reservoir. There are three sources of nutrition input into the reservoir: precipitation, river and periphery district. The pollution from periphery district can be divided into point source and non point source.The gross nutrition from the precipitation was obtained by monitoring the quality and the quantity of the precipitation of periphery district. The water quality and volume of the major river such as Qingshui River, Duijia River and White Maguan River had been measured and their nutrient contribution to the reservoir had been calculated too. For point source pollution, the nutrition was contributed by various sources: animal wastes, human feces, inn and restaurant in tour sight spot. For nonpoint source pollution, the consumption of fertilizer and pesticide was investigated. Collected the data information of periphery district, which included Digital Elevation Model, Landsat7 TM remote sensing reflection, the soil profile and the rainfall data of Xiahui, Zhangjiafen, Chaohe and Baihe rainfall station. Translated the remote sensing reflection and investigated the spot by unsupervised classification and supervised classification of ERDAS. As a result, the periphery district land utilization type picture was generated. Supported by ERDAS and Visual Basic software, the layer of soil erodibility factor, slope length and steepness factor, crop management factor and conservation practice factor were also got. The nonpoint source pollution from the periphery district was calculated by applying theUniversal Soil Loss Equation. The profile of the runoff of nitrogen and phosphorus element was provided. The total pollutant imports and the load within land in different utilization were calculated respectively.In MiYun Reservoir, the pollution was contributed more by nonpoint source than point source. The point source pollution in the periphery district only contributed 2.92% of nitrogen and 4.30% of phosphorous of the whole nutrient inputted into the reservoir. However, animal wastes were the major pollution source in all of the point source.The periphery district soil erosion was the primary pollution in the nonpoint source, which contributed 60.23% of nitrogen and, 90.87% of phosphorus. Topography and vegetation cover rate were two of the most important influence factors of nonpoint source pollution. The total runoffs of nitrogen and phosphorus element were 143.73 tons and 0.354 tons respectively which were mainly caused by the fertilizer from the farmland. The precipitation contributed 109.07 tons and 1.20 tons nitrogen and the phosphorus, which was the second important pollution source. Monitoring was conducted on the Qingshui River, Duijia River and White Maguan River. There was no water in the Qingshui River in whole flood season. In the water body of Duijia River and White Maguan River, the nitrogen nutrient content was higher than other elements, while the water quality was acceptable. The water quality met the standard of the national surface water II. In the flood season, 61.55 tons of nitrogen and 1.24 tons of phosphorus were inputted into reservoir respectively.In conclusion, the input of nutrient within this research scope has significant influence to reservoir water quality. If the water capacity of the reservoir was counted as 1.0×109m3 and ignored the export of reservoir nutrient, the nitrogen and phosphorus will increase 0.463mg/L and 0.051mg/L respectivel...
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