Nonpoint Source Pollution Assessment of Wujiang RiverWatershed in Guizhou Province,SW China |
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Authors: | Cong-Guo Tang Cong-Qiang Liu |
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Institution: | (1) State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550002, China;(2) Graduate School, Chinese Academy of Sciences, Beijing, 100039, China |
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Abstract: | The amount of pollution from nonpoint sources flowing in the streams of the Wujiang River watershed in Guizhou Province, SW
China, is estimated by a geographic information system (GIS)-based method using rainfall, surface runoff and land use data.
A grid of cells of 100 m in size is laid over the landscape. For each cell, mean annual surface runoff is estimated from rainfall
and percent land use, and expected pollutant concentration is estimated from land use. The product of surface runoff and concentration
gives expected pollutant loading from that cell. These loadings are accumulated going downstream to give the expected annual
pollutant loadings in streams and rivers. By dividing these accumulated loadings by the similarly accumulated mean annual
surface runoff, the expected pollutant concentration from nonpoint sources is determined for each location in a stream or
river. Observed pollutant concentrations in the watershed are averaged at each sample point and compared to the expected concentrations
at the same locations determined from the grid cell model. In general, annual nonpoint source nutrient loadings in the Wujiang
River watershed are seen to be predominantly from the agricultural and meadow areas. The total annual loadings through the
outlet of the watershed are 40,309 and 2,607 tons for total nitrogen (TN) and total phosphorus (TP), respectively. |
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Keywords: | GIS Nonpoint source pollution Watershed Grid model Loading Total nitrogen Total phosphorus |
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