Study On Agricultural Non-Point Source Pollution Of Heigou Watershed In Danjiang Reservoir Area

The load composition of water pollution has been changed obviously with the effectively control on point source pollution in recent years. Non-point source (NPS) pollution has become the chief cause of water contamination and lake eutrophication especially agriculture NPS pollution. As the water source of middle route line of South-to-North Water Transfer Project, the water quality of Danjiang reservoir is at good situation and is suitable for water transfer in general. But it is reported that some branches of the upriver are in bad situation, which are mainly caused by agriculture NPS pollution .Therefore, it is important to study the agriculture NPS pollution for protecting the water quality of Danjiang reservoir.Firstly, Heigou watershed in Danjiang reservoir area was chosen as the study object. The actuality of agriculture non-point source pollution in this area was studied based on comprehensive investigation. An agriculture non-point pollution model: AnnAGNPS was introduced to simulate the load of sediment, nitrogen, phosphorus etc in 2004. The feasibility to use this model in Danjiang reservoir area, typical foothill, was proved. The results showed:(1) There were 16714.81 tons sediment, 91.82 tons total nitrogen and 4.49 tons total phosphorus discharged from the Heigou watershed. The clay particles(<0.002mm) was the main form of sediment. The soluble nitrogen was the main form of TN loading, whereas sediment phosphorus was the dominant form of TP.(2) Monthly output loading changed very strongly and the loading was interrelated positively with rainfall. The dates of maximum of pollutant in the outlet was mostly in April-October month .Sediment,TN and TP contributed 87.80%, 90.10% and 86.82% respectively during the April and October in which accounted for 95% in 2004.(3) The loads of pollutant were influenced significantly by landuse types. The total pollutant loading was as follows: cropland > wasteland > woodland > resident > orchard. The pollutant loading per area was different, and the sediment was in the following order: cropland > orchard > wasteland > resident > woodland, whereas...