Study of pollution from agricultural nonpoint sources in Lake Erhai watershed in Yunnan Province based on export coefficient model
ZHANG Chen1， LU Jianzhong1， CHEN Xiaoling1,2
1. State Key Laboratory of Information Engineering in Surveying，Mapping and Remote Sensing，Wuhan University，Wuhan 430079； 2. Key Laboratory of Poyang Lake Wetland and Watershed Research of Ministry of Education，Jiangxi Normal University，Nanchang 330022
Abstract：The subwatershed of Lake Erhai watershed， including Luoshijing， Mijvhe and Yonganjing， which are located in the north area， are served as the experimental area. The export coefficient is utilized to calculate the total nitrogen(TN) and total phosphorus(TP) loads from agricultural nonpoint sources(NPS) of this experimental area. The export coefficients of this model are calibrated and validated with the water quality monitoring data of the experimental area， aiming to get the export coefficients that could be used in the whole area of Lake Erhai watershed more effectively. The TN and TP loads from agricultural nonpoint sources of the whole Erhai watershed is calculated by the export coefficients. Our results suggest that the pollution from nitrogen and phosphorus have a high correlation， and their spatial distributions show the trend that the north and south of this area contribute more than the middle area. For TN loads， the magnitude order of the contribution was as follows： cattle breeding> rural life> farming> pig breeding. For TP loads， the magnitude order of the contribution was as follows： farming> rural life> pig breeding> cattle breeding.
