基于非点源污染入河估算下杭嘉湖地区河网水质模拟分析

Simulation analysis of river network water quality in Hangzhou-Jiaxing-Huzhou area based on estimate of non-point source pollution

杭嘉湖地区河网水质主要受上游河流水质、点源污染以及伴随径流过程的非点源污染的影响。在水质模拟中,非点源污染对河网水质的影响往往较大,但目前缺乏相关方法来定量描述非点源污染的入河系数与其距河道距离的关系。综合考虑了平原河网的水流特性以及污染物在径流过程中的衰减作用,推求了计算非点源污染入河系数与距离之间定量关系的公式,利用基于此公式改进的水动力水质耦合模型探究研究区域内各污染源对其内部河网水质的影响。结果表明:相较于传统计算方法,非点源污染入河量采用该公式的计算时,研究区域氨氮和总磷模拟误差分别降低了2.13%和3.83%。农业种植是影响杭嘉湖地区水质最重要的因素,在没有农业种植污染的情况下,模型内验证站点氨氮浓度降低了45.27%,总磷浓度降低了24.16%。各污染源对杭嘉湖地区河网水质影响程度排序为:农业种植>点源污染>畜禽养殖>生活废水>水产养殖。

The water quality of the river network in the Hangzhou-Jiaxing-Huzhou area is mainly affected by the water quality of the upstream river,point source pollution and non-point source pollution accompanying the runoff process.In the water quality simulation,the impact of non-point source pollution on the water quality of river networks is often large,but there is currently no relevant method to quantitatively describe the relationship between the inflow coefficient of non-point source pollution and its distance from the river.Considering the water flow characteristics of the plain river network,the formula for calculating the quantitative relationship between the non-point source pollution into the river coefficient and the distance is derived under certain conditions,and the hydrodynamic water quality coupling model based on this formula is used to explore the research area.The impact of pollution sources on the quality of its internal river network.The results show that Compared with the traditional calculation method,the simulation results of non-point source pollution into the river using this formula,the simulation errors of ammonia nitrogen and total phosphorus in the study area were reduced by 2.13%and 3.83%,respectively.Agricultural planting is the most important factor affecting the water quality in the Hangjiahu area.In the absence of agricultural planting pollution,the ammonia nitrogen concentration in the model verification site decreased by 45.27%and the total phosphorus concentration decreased by 24.16%.The degree of influence of various pollution sources on the water quality of the river network in the Hangjiahu area is:agricultural planting>point source pollution>livestock and poultry farming>domestic wastewater>aquaculture.