海河干流汛期动态水环境容量计算研究

海河干流是一个典型的平原缓滞流型河道,水体自净能力低,且汛期大量污染物随降雨径流汇入,水污染问题严重。水环境容量的计算是实施污染控制的基础,对水环境质量管理方案的制订具有重要意义。在汛期,海河干流受降雨径流和闸门控制等因素的多重影响,其水位、流量、水质等要素随时间变化十分复杂。为此,提出基于水动力水质模型的河流动态水环境容量计算方法,计算了海河干流4个控制单元汛期COD、TN、TP的水环境容量。结果表明:海河干流水体污染严重,各控制单元现状条件下TN及TP几乎没有可利用的水环境容量。在此基础上,对天津市中心城区及环城四区选取透水铺装、下凹绿地、绿色屋顶和生物滞留设施等4种措施进行低影响开发改造,并在SWMM模型中模拟改造效果。改造后,研究区域内COD、TN、TP入河量的削减率分别达到39.5%,35.7%,35.9%,且各个控制单元汛期水环境容量均有明显提高。研究结果可为海河干流水环境质量管理提供依据,为缓解降雨径流污染、改善水环境质量提供技术支撑。

Study on dynamic water environmental capacity of mainstream of Haihe River in flood season

The main stream of Haihe River is a typical slow-lagging plain channel with low capacity for self-purification,and a large number of rainfall-runoff pollutants in flood season causes serious water pollution problem. The calculation of water environmental capacity is the basis of pollution control and is of great significance to the formulation of water environmental quality management scheme. During the flood season, the water level, flow and water quality of the main stream of Haihe River change over time in complex ways affected by multiple factors, such as rainfall-runoff and sluice control. Therefore, a dynamic calculation method based on hydrodynamic and water quality model is proposed to calculate the water environmental capacity of COD, TN, TP of the four control units of the main stream of Haihe River in flood season. The results show that there is almost no available water environmental capacity of TN and TP under the current conditions. Besides, a low-impact development scheme including permeable pavement, concave green land,green roof and bioretention facilities was proposed and the effect was simulated in SWMM model. Under low-impact development, the reduction rates of pollutant quantity inlets into river of COD, TN and TP were 39.5%, 35.7% and 35.9%, respectively. And the water environmental capacity of each control unit in flood season has been significantly improved. This study can provide the basis for the management of the water quality of the Haihe River, as well as the technical support for alleviating the rainfall-runoff pollution and improving the water environment quality.