基于SWAT模型的丹江口水库流域农业非点源污染的时空分布特征

利用SWAT模型，基于GIS技术和流域DEM，构建了丹江口水库流域农业非点源污染基础信息库，并根据实测资料对模型的参数进行了率定和验证，在确定模型适用性的基础上分析了流域农业非点源污染负荷的时空分布特征，模拟计算了流域内主要的土地利用类型的单位面积农业非点源污染负荷量。结果表明：研究区农业非点源污染负荷年内分布不均，污染负荷与降雨量具有较强的相关性，氮负荷同月径流的相关系数为0896，磷负荷同泥沙负荷的相关系数为0920；氮、磷等营养物质的流失量具有较大的空间差异性，且不同土地利用方式下单位面积的农业非点源污染有较大的差别，耕地和裸露地的单位面积污染负荷均较高，而林地单位面积的泥沙负荷污染负荷最低，其单位面积的泥沙负荷、吸附态氮、溶解态氮、吸附态磷和溶解态磷分别为715 t/hm2、892 kg/hm2、835 kg/hm2、807 kg/hm2、006 kg/hm2；设计不同的情景，模拟了不同施肥量和水土保持措施对农业非点源污染物产出的影响，与基准情景相比，发现减少化肥施用水平对研究区农业非点源污染总氮和总磷负荷削减比例较大，采取退耕还林和还草两种水土保持措施能有效减少流域泥沙负荷和农业非点源污染负荷

TEMPORAL-SPATIAL DISTRIBUTION OF AGRICULTURAL NON-POINT SOURCE POLLUTION IN THE DANJIANGKOU RESERVOIR WATERSHED BASED ON SWAT MODE

The Danjiangkou reservoir watershed is the source region of middle route of the South to North Water Transfer Project.However,agricultural non point source pollution is threatening the security of water environment in the watershed.Based on Geographic Information System (GIS) and Digital Elevation Model (DEM),the database of agricultural non point source pollution for the reservoir watershed was established.According to the filed measured data,Soil and Water Assessment Tools (SWAT) were adjusted to analyze the temporal spatial distribution patterns of non point source pollution load in the watershed.The agricultural non point source pollution loads per unit area of major land use types were also calculated.Results showed that there was a greater temporal difference in the output of agricultural non point source pollution within the year in the watershed (p<001).The load of agricultural non point source was strongly correlated with rainfall (rN=0896，rP=0920,p=001),sediment storage,ammonia nitrogen,total nitrogen and total phosphorus in the rainy period of June,July,August,accounted for 576%,64%,501%,508% and 473% of total year.The loss amount of soil nutrient such as nitrogen and phosphorus showed a great spatial variability in the watershed (p<001).Both farmland and bare land had a high contribution to the non point source pollution load,whereas the contribution of forest to the pollution load was low.Its sediment load per unit area,nitrogen adsorption,dissolved nitrogen,phosphorus sorption and dissolved phosphorus were 715 t/hm2,892 kg/hm2,835 kg/hm2,807 kg/hm2,006 kg/hm2,respectively.This suggested that the agricultural non point source pollution per unit area under different types of land use was obviously different.Under the simulated scenarios including different fertilizing amount and soil and water conservation measures,the reduction of fertilizing amount could effectively decline the pollution load of total nitrogen and total phosphorus,and returning farmland to forests or grasslands could notably reduce the output of sediment from farmland to river as well as the load of agricultural non point source pollution in the watershed