城镇暴雨初期雨水产流与产污模拟研究

Simulation of Runoff and Pollution Production During the Initial Rainfall of Urban Rainstorm

降雨过程中形成的污染已成为重要的城市面源污染,尤其是降雨初期雨水对城市地表的冲刷导致大量的污染物排放入水体,造成城市河流的冲击性污染。当城镇遭遇暴雨时,下垫面硬化和污染物积蓄使得初雨污染峰值过程更剧烈,对河流的水质影响更为严重。本文采用暴雨洪水管理模型(storm watermanagementmodel,SWMM)平台对具有不同下垫面特性的城镇流域开展暴雨条件下的径流模拟,在此基础上开展面源污染产生过程模拟,对比研究不同下垫面特性对产流、产污过程的影响。结果表明:降雨强度越大,径流产流速度越快,径流峰值流量越大;流域中建成区占比越高,产生的径流量越大,单位面积产污量线性增大。建成区占比高的流域产污过程线较尖瘦(峰值相对较大但历时较短),受支流汇流历时影响,干流产流过程线形状比支流宽胖(峰值相对较小但历时较长),干流峰值比支流滞后10~14 h。暴雨后期地面冲刷的污染物浓度随时间降低,干流的产污过程峰值相对于支流滞后不显著。研究成果可为城镇初期雨水污染防治的技术实施提供理论支撑,对消除城镇黑臭水体和维护河流水环境健康具有指导意义。

Pollution formed during rainfall has become a significant factor influencing urban area-source pollution.Rainwater flushes the urban surface in its early stages and brings a large accumulation of pollutants into water body of the urban river.Espe⁃cially,during heavy rainstorm,the hardening of the substratum and the accumulation of pollutants make the peak process of the ini⁃tial rain pollution more intense,and the influence on river quality is more severe.In this paper,the storm water management mod⁃el(SWMM)was used to simulate the pollution generation process for urban runoff under heavy rainstorm conditions and with differ⁃ent substratum characteristics,and the effects of different substratum on the flow and the pollutions production process were com⁃pared.The results show that the higher rainstorm intensity,the faster runoff production and the higher peak flow rate;and that the larger built-up areas in the watershed,the higher the peak flow rate,and the pollution production per unit area increased linearly.For high proportion of built-up area,the process line of pollution generation is more sharp and thin,indicating a relatively higher pollution generation in a shorter time period.The process line of pollution production in mainstream is wider and fatter(i.e.relative⁃ly low peak and longer time period)than that in the tributaries due to the time lag of confluence of the tributary inflow,and the mainstream peak value lags behind that of the tributaries by about10~14 hours.During the later stage of a rainstorm,the concentra⁃tion of pollutants from ground scouring gradually decreases,and the time lag between the pollution production peaks of the main⁃stream and the tributaries is not obvious.The study provides a support to the prevention and control of urban river water environ⁃mental protection during rainstorm.