Simulation and analysis of non-point source pollution in the polder region of Dongting Lake

Dongting Lake,the second largest freshwater lake in China,is recently subjected to a trend of deterioration of water quality and eutrophication problem,and non-point source pollution has become a major source of its water pollution.In this paper,a distributed non-point source pollution model is developed to estimate the load and discharge amounts of such nitrogen and phosphorus sources in the Dongting polder region,and the causes and the spatial and temporal distribution of such sources over the study area are analyzed.The results of simulation and analysis indicate that dissolved nitrogen and phosphorus are the major sources,about 75% of it generated in flood season.Farmland rainfall-runoff contributes about 70%,and livestock's contribution to these sources comes next.In the study area,over 70% of these pollutants are discharged into the rivers and lake.This work would be a reference to the protection of Dongting water environments.