Simulating Non-Point Pollution at Watershed Scale: A Case Study in Dagu Watershed
大沽河典型小流域非点源污染模拟

Surface waters can be polluted mainly by emissions and discharges from such two types as point sources and non-point sources. Point-source pollution for the most part are under control and well regulated by governmental agencies, while the control of emissions and discharges from non-point sources are much more harder and being increasingly recognized as significant sources of pollution. Non-point-source pollution simulation has been considered as a cost-effective and time-efficient method for assessing pollution situation and selecting management practices.AnnAGNPS model created by Ministry of Agriculture of USA has been widely used for non-point pollution management worldwide. In China, AnnAGNPS model has been used in the coastal region of southeast of Zhejiang and Fujian provinces. less work has been done to use the model assessing the pollution situation in eastern zones where surface and ground water were seriously polluted by intensively agricultural activities. In this paper, a case study was conducted in Dagu watershed, which covering a land area of 610.81square kilometer and located in Shandong Peninsula of China. The attributes of watersheds, tributary channels and main channel in each cell were generated using ArcView-AnnAGNPS interface. And the model was separately calibrated and validated using observed data in the watershed during the period of 2000 to 2001. The predicted and observed results of runoff, sediment, and total nitrogen content on a daily basis were poorly correlated, and the corresponding results on annual basis were performed well. Considering that AnnAGNPS in the current study was primarily intended as a tool for long-term conservation planning and BMP (Best Management Practice) selection, its performance was adequate. Daily performance for water, sediment and total nitrogen content was poor. Generally, the model can be used in Dagu watershed for comparative assessment, gross estimation of volume of runoff, sediment and total nitrogen content, and the selection of BMP. The result showed that the reforestation project, which simultaneously minified the amount of runoff, sediment and total nitrogen should be adopted in Dagu watershed in order to control non-point pollution. It is expected that this study could provide a reference for selecting appropriate parameters and coefficients in application of AnnAGNPS model in eastern China and somewhere else.