Research On Agriculture Non-point Source Of Nitrogen And Phosphorus Load About Zhaowang Watershed Based On AnnAGNPS

In recent years,as people concerned more about environmental issues,point source pollution have been commendably controled and governed in many countries,including our country.For now, the non-point source pollution has become the major pollution souce in the water environment,for it involves a wide range of contaminants and hard to controled and govened. And the agricultural non-point source pollution have become a top priority as the main types of non-point souce pollution.AnnAGNPS was a continuous distributed parameter model that developed by the U.S. Department of Agriculture.lt can be used to estimate the non-point souce pollution loads and environmental influence of agricultural watershed.This study was based on the AnnAGNPS and selected the Zhaowang River as the study area which is located in Liaocheng,Shandong Province.The ArcGIS has been used in this study to build digital elevation model. Zhaowang River AnnAGNPS model database was established through data collection firstly,and then the model's suitability in Zhaowang River was validated through the actual rainfall event simulation.Finally,the temporal and spatial distribution characteristics of the nitrogen and phosphorus was simulated by calibrated AnnAGNPS model.Then the quantitative evaluation have been made to see the effects of pollution reduction of the beat management practices.The following conclusions were obtained in the paper:1. The total amount of offrun output of Zhaowang Watershed in 2008 is 5.29×107m3;the total amount of nitrogen output in basin outlet is 1142.3t,which is including dissolved nitrogen 1038.4t,and absorbed inorganic nitrogen 103.9t;the total amount of phosphorus was 175.7t,which is including dissolved phosphorus 19.4t,and absorbed inorgannic phosphorus 155.6t. The export of dissolved nitrogen was the mainly part of N exportion,and the absorbed phosphorts was the mainly part of P exportion.2. The pollution load of TN and TP was mainly occured in June to August.During the petiod,the nitrogen load was accounted for 73% and the phosphorus load was accounted for 73%,and both reached its peak in July.The relationship of Zhaowang Watershed non-point source pollution load and rainfall was basicly positive correlation.3. The notrogen loss produced by non-point source occurs mainly in middle and lower basin, while the phosphorus loss is relatively smaller, and mainly in the middle part of the basin. The pollution load is closely related to soil types.For example:the loss of total nitrogen and dissolved nitrogen was mainly occurred in the humid-soil,while the loss of total phosphorus and absorbed phosphorus was mainly in saline soil and salted soil.4. Adoption of riparian buffer strips in parallel with the balanced fertilization can batter reduce non-point source pollution.Finally, on the basis of designing the best management practices rationally, we give some methods and advice on control and management for the agricultural non-point source pollution of Zhaowang watershed.