基于SWAT模型的观澜河流域城市面源污染负荷量化及影响效应评估

Load quantification and effect evaluation of urban non-point source pollution in the Guanlan river basin based on SWAT model

随着我国城市区域污水收集、截污系统的完善与水质净化厂出水标准的提高,点源污染逐步得到控制,城市面源污染对河流水质的影响越来越凸显。针对当前城市内河流集水区域城市面源污染负荷难以量化、对水体水质影响效应难以解析等问题,以深圳市观澜河流域为研究对象,通过对流域的现场勘察调研与地表累积物采样研究,来修正流域土地利用类型数据与SWAT模型的城镇数据库,构建流域城市面源污染评价模型。结果表明:SWAT模型城镇数据库中地表沉积物最大累积量(DIRTMX)、地表沉积物中总氮含量(TNCONC)、地表灰尘累积半饱和时长(TNALF)与地表灰尘总磷含量(TPCONC)对TN与TP负荷的模拟最为敏感;建立的SWAT模型对观澜河流域径流量、TP与TN模拟验证期的纳什效率系数(ENS)分别为0.79、0.7、0.67,决定系数(R2)分别为0.81、0.77、0.81,模型拟合结果较好。应用SWAT模型分析了2018年观澜河流域TN和TP的城市面源污染时空分布特征:TN和TP输出最高值为13.31~14.91 t·km^-2和1.69~1.86 t·km^-2;8月份观澜河流域降雨径流污染最为严重,TN和TP负荷分别为2.15 t·km^-2与0.24 t·km^-2。上述评估结果可为区域城市面源污染的负荷量化与影响效应评估提供参考。

In recent years,with the improvements of sewage collection,interception systems in urban region of China and effluent standards of water purification plants,point source pollution has been gradually controlled,and the impact of urban non-point source pollution on water quality of river has becoming more and more significant.Aiming at the problems such as being difficult to quantify the current urban non-point source pollution load in river catchment areas of cities and to analyze the impact on water quality,Shenzhen Guanlan river basin was taken as the research object,site survey and investigation of land surface accumulation were performed in the river basin,then the land use type data of the river basin and the urban database of SWAT model were revised to build an urban non-point source pollution assessment model.The results showed that in the urban database of SWAT model,maximum accumulation of land surface sediments(DIRTMX),TN in land surface sediments(TNCONC),half saturation time of land surface dust accumulation(TNALF)and TP in land surface dust(TPCONC)were most sensitive to the simulation of TN and TP loads.Nash efficiency coefficients(ENS)of the built SWAT model for the runoff of the Guanlan river basin,TP and TN simulation verification periods were 0.79,0.7 and 0.67,the corresponding coefficients of determination(R2)were 0.81,0.77 and 0.81,respectively.The model simulation results were good.The built SWAT model was used to analyze the spatiotemporal distribution characteristics of urban non-point source pollution of TN and TP in the Guanlan river basin in 2018.The highest values of TN and TP export were 13.31~14.91 t·km^-2 and 1.69~1.86 t·km^-2.In August,rainfall runoff pollution in the Guanlan river basin was the most serious,and TN and TP loads were2.15 t·km^-2 and 0.24 t·km^-2,respectively.The result can provide reference for load quantification and effect evaluation of regional urban non-point source pollution.