[Objective] Agricultural non-point source pollution was the main cause of water eutrophication in hilly area of purple soils.The small watershed in purple soil area experienced intense farming activities,however,the agricultural watersheds in this area were the lack of observed data and prediction tools of nitrogen and phosphorus export fluxes from agricultural catchments.Therefore,it is difficult to develop good solutions aiming at the mitigation of nitrogen and phosphorus in small watershed scale.[Method] In the present study,SWAT was used in a watershed with area of 12.36 km2 in typical purple soil region of upper Yangtze River.According to the measured data,SWAT model was adjusted to simulate the river discharge and non-point source pollution processes.[Resuh] SWAT succeeded in of monthly and daily discharge simulation with satisfactory performance in the study area (R2 =0.6-0.9,Ens =0.55-0.9),and SWAT could simulate the transportation of nitrogen and phosphorus with good fitness based on monthly interval (R2 =0.75-0.91,Ens =0.72-0.80).It was proved the SWAT could be successively applied in a complex agricultural watershed (10 km2) at hilly area of purple soil.[Conclusion] The critical source areas for non-point source nitrogen and phosphorus were identified,so as to formulate countermeasures preventing nonpoint source pollutions in the study region.%[目的]农业非点源污染是造成水体富营养化的重要形式,紫色土丘陵区小流域农耕活动频繁,缺乏对农事操作所导致的氮、磷迁移通量的模拟和预测工具,从而难以针对小流域尺度氮、磷流失制定优化的非点源污染减控措施.[方法]本研究将SWAT运用在面积为12.36 km2的典型紫色土丘陵区农业小流域.通过实测数据率定模型参数,模拟了小流域水文过程和氮、磷污染物迁移过程.[结果]SWAT2012能够很好地模拟每日径流、泥沙输出(决定系数R2＞ 0.60,纳什系数Ens ＞0.55),同时可模拟月步长氮、磷污染物输出过程(决定系数R2 ＞0.75,纳什系数Ens＞0.72),说明SWAT模型可有效地进行丘陵区较小尺度小流域(10 km2)面源污染输移模拟和预测.[结论]模拟结果可得出,氮、磷污染物的关键源区主要位于小流域沟谷区,通过建设河岸缓冲带可有效防止地表和地下径流途径的氮、磷损失.
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