基于LOADEST和数字滤波的水源地基流氮素输出定量方法应用实例

地表直接径流和基流均是流域非点源氮/磷养分输出的重要水文途径.科学认识和定量模拟基流氮/磷养分输出对于准确解析水源地水体非点源污染来源至关重要.基于Load Estimator模型和数字滤波算法,建立了定量水源地基流氮素输出的方法体系.以浙江省珊溪水源地的玉泉溪流域为例,利用玉泉溪2010-01—2013-12期间逐月总氮(TN)水质监测数据和逐日流量数据,展示了该方法的计算过程.结果表明,本文建立的水源地基流氮素输出定量方法结果合理,模拟精度高,决定系数和纳什系数分别为0.83和0.80;玉泉溪流域2010—2013年TN负荷量为141.21～274.68 t·a~(-1),平均208.63 t·a~(-1),年基流TN负荷量为84.39～168.68 t·a~(-1),平均127.69 t·a~(-1);基流对玉泉溪年均TN负荷量贡献率高达60%以上,流域基流养分输出对地表水体的污染应引起足够重视.

Case study of the quantification of baseflow nitrogen export using LOADEST and digital filtering in drinking water source region

Surface direct runoff and baseflow are two main pathways of non-point source nitrogen/phosphorus nutrient transporting to streams. Scientific understanding and quantitative analysis on baseflow nitrogen load are essential for accurately tracking the non-point sources of nitrogen pollution. This paper applied Load Estimator model and digital filtering algorithm to quantify baseflow nitrogen load and Yu Quan River watershed drinking water source region in Shanxi, Zhejiang province, was used as the study site. Monthly total nitrogen concentration and daily stream discharge records during 2010-01-2013-12 in Yu Quan River watershed were used. The results show that the methodology used in this study could yield reasonable outcome with high simulation accuracy, the determination coefficient and Nash-Sutcliffe model efficiency were 0.83 and 0.80, respectively; the annual riverine TN loads ranged from 141.21 to 274.68 t·a^-1 with an average value of 208.63 t·a^-1, annual baseflow driving TN loads from 84.39 to 168.68 t·a^-1 with an average value of 127.69 t·a^-1; the annual contribution of baseflow to riverine TN pollution was more than 60%, which needs enough attentions on the surface water quality impairment caused by baseflow nutrient export.