基于SWAT模型的北京沙河水库流域非点源污染模拟

Simulation of non-point source pollution in the Shahe Reservoir catchment in Beijing by using SWAT model

该文应用分布式水文模型SWAT,以北京昌平沙河水库流域为典型区开展研究,通过对流域非点源污染的调查、监测和模拟,定量计算和分析了非点源污染时空分布规律。结果表明:该模型在研究区适用性较好(月径流率定期R2=0.85,Nash-Sutcliffe效率系数为0.64;验证期R2=0.77,Nash-Sutcliffe效率系数为0.60),非点源污染占污染负荷总量的30～50%,汛期集中了全年泥沙、总磷流失量的70%和总氮流失量的50%,南沙河子流域是污染负荷的关键区。通过研究不同水文条件、土地利用和管理措施对流域非点源污染的影响,得出结论:非点源污染负荷贡献率随降雨量增加而增加,其偏枯水年贡献率为27.4%,平水年36.7%,丰水年52.3%。若全部排污口实施达标排放、流域内全部农田改为林地,径流量、氮磷负荷量均会减少40%～50%;若实施化肥施用量减半,氮磷负荷可降低20%左右。氮元素不同土地利用单位面积负荷由高到低依次为:果园>农田>草地>林地>城镇用地,研究成果将为流域水资源保护规划提供科学依据。

In this study,Soil and Water Assessment Tool（SWAT） was used to simulate the river discharge and Non-Point Source（NPS） pollution processes in the Shahe Reservoir catchment in Beijing.The model was run with data of ten years period（1999-2008）.The simulation results of monthly discharge,total nitrogen（TN） and total phosphorus（TP） showed that the SWAT model performed satisfactorily in the study area（R2=0.77～0.85,Ens=0.60～0.64 for monthly discharge;R2=0.65～0.78,Ens=0.53～0.72 for TN and TP）.The NPS pollution contribution increased with the precipitation,which accounted for 30%～50% of total pollution in different hydrologic years.Nanshahe sub-watershed was the critical area in the pollution.The sediment and TP accounted for 70% of the total volume in the flood period from June to September.In addition,seven scenarios ware set up to analyze the degree of NPS pollution within different hydrological conditions,landuses and management measures by using SWAT model.Results show that,if all point sources reach,the standard level,and all farmland is change into forest,discharge and pollutant loads will decrease by 45%～50%.Pollutant loads will decrease by nearly 20% with the decrease of fertilizer uses.Nitrogen load per unit area in ranks is：orchard farmland pasture forest urban land.This study provides important scientific basis for the planning and management of the water resources in the Shahe Reservoir catchment.