基于GWLF模型的于桥水库流域氮磷负荷估算及来源变化解析

外源氮磷污染物输入是于桥水库富营养化加剧的主要原因之一。为了研究“水十条”实施以来于桥水库流域氮磷污染负荷的变化,采用GWLF模型模拟各个子流域产流量,再乘以子流域出口断面总氮（TN）、总磷（TP）监测浓度,进而估算整个流域氮磷污染负荷,并对2016—2017年氮磷污染的来源和变化情况进行分析。结果显示：2016—2017年于桥水库流域年均TN负荷2 574.6 t,TP负荷94.6 t。引滦调水、入境河流、库周产流和大气降水对TN的贡献占比分别为27.9%、46.8%、17.3%和8.0%,对TP贡献占比分别为66.3%、17.3%、13.6%和2.8%。与2016年相比,2017年流域TN负荷增加35.6%,主要是由于引滦调水TN浓度大幅上升（增幅239%）、沙河等流域产流量增加（增幅11.4%）导致;2017年流域TP负荷减少74.0%,主要是由于引滦调水和沙河等河流TP浓度均明显下降（降幅分别为87.8%和71.0%）导致。因此,建议于桥水库流域环境管理部门加强总氮面源污染防控,同时选择大黑汀水库氮磷浓度较低的时期调水,以减少氮磷污染负荷。

Load estimation and source variation analysis of nitrogen and phosphorus for the Yuqiao reservoir watershed based on the GWLF model

The input of exogenous nitrogen and phosphorus is one of the primary reasons for the escalating eutrophication issues of the Yuqiao reservoir. The GWLF model was used to study the change of nitrogen and phosphorus pollution loads in the Yuqiao reservoir watershed since the implementation of the "Action Plan for Prevention and Control of Water Pollution". The model simulated the hydrological water yield in the watershed, estimated the nutrient loads by multiplying the simulated streamflow at the subbasin outlet by the observed total nitrogen(TN)and phosphorus(TP)concentration data at the same site, and analyzed the source and change of the TN and TP loads from 2016 to 2017. Results showed that the average annual TN and TP loads of the Yuqiao reservoir watershed from 2016 to 2017 were 2 574.6 t and 94.6 t, respectively. The contribution of water diversion from the Luanhe River, upstream incoming rivers, runoff around the reservoir, and atmospheric precipitation to the TN load accounted for 27.9%, 46.8%, 17.3%, and 8.0%, respectively. For the TP load, the aforementioned contributing factors accounted for 66.3%, 17.3%, 13.6%, and 2.8%, respectively. Compared with that of 2016, the TN load in the watershed increased by 35.6%, primarily because of the increase of the TN concentration of water diverted from the Luanhe River by 239% and the increase of the water yield in the watershed of upstream incoming rivers by 11.4% in 2017. The TP load in the watershed decreased by 74.0%, primarily because of the decrease of the TP concentration of water diverted from the Luanhe River and the upstream incoming rivers by 87.8% and 71.0%, respectively. The water environmental management department of the Yuqiao reservoir watershed should strengthen the prevention and control of TN source pollution and simultaneously divert water from the Luanhe River during periods of low nitrogen and phosphorus concentrations to reduce the input of the TN and TP loads.