Prediction on pollution contribution of N and P from agricultural non-point source pollution in Poyang Lake watershed

Non-point source pollution from agriculture is a major cause of water quality problems, above all, nutrients such as Nitrogen (N) and Phosphorus (P) from various land-use become the leading factors on lake water eutrophication. The Poyang Lake is the biggest fresh lake in China, which has principal ecological function for the Yangtze River. With agriculture dramatically developing in the watershed, water quality in the Lake has degraded and water eutrophication has been increasing. Based on data from the national agricultural pollution source census and provincial water quality monitoring in 2007, the load of N and P from agriculture pollution at watershed scale has been assessed by using the Transportation Parameter Model and RUSLE Model, in order to analyze pollution contribution of N and P from agriculture to the Poyang watershed water pollution. The result suggested that load of N and P from agricultural pollution in the Ganjiang River subwatershed were the greatest in the Poyang Lake watershed, which were 12504.3 ton and 507.0 ton, respectively, accounting for 48.1% and 46.9% of total loads all over the watershed. The transportation capacity of N and P from agricultural pollution around the Lake area were greater than the others subwatersheds, which were 2.33 kg/ha and 0.11 kg/ha, respectively. Contributions of N and P from agricultural pollution around the Lake area were 81.5% and 64.8%, and the former was greater than the latter remarkably. Therefore, the Ganjiang River subwatershed and around the Lake area were sensitive area of non-point source pollution from agriculture, nutrients such as N and P from agricultural land were the crucial source of water pollution in the Lake, and the two subwatershed should launch agricultural pollution management practice.