海绵城市建设中若干水文学问题的研讨

针对海绵城市建设面临的问题和挑战,提出了以水循环为纽带、将城市暴雨-径流、水污染治理和城市生态绿地、湿地建设与市政建设(排水、排污)规划管理联系为一体的"城市水系统"的概念与方法。基于水文学原理,分析了目前海绵城市建设中最为关键、也是质疑较多的年径流总量控制率概念,指出现行的年径流总量控制率的计算实质是年降水总量控制率。如果回归到水文学概念,年径流总量控制率就必须与水文系统响应的增益因子,即径流系数建立内在的联系;需要研究径流系数并非常数,而是与土壤湿度、降水强度和下垫面组合的时变非线性理论问题。此外,对比分析了现行海绵城市建设低影响开发措施和改进后的年径流总量控制率之间的关系,深入剖析了"城市看海"发生的条件与风险。最后就海绵城市建设与规划的水文学基础亟待改进的方面:径流系数非线性、区分自然条件和城市化后的蓄水量变化的差别、考虑河湖水系调蓄和陆地蒸散发、与流域大海绵调控结合、风险管理等,进行了研讨,并提出了未来我国海绵城市建设的若干建议。

Discussion of several hydrological issues regarding sponge city construction

Based on a review of the problems and challenges of sponge city construction in China, the concept and methodology of an urban water system integrating urban rainstorm-runoff, water pollution control, and an urban ecological greenbelt with wetland and municipal construction(drainage and sewage)are proposed. Based on hydrological theories, the concept of the control rate of total annual runoff, which is the most critical and difficult-to-quantify factor in the construction of a sponge city, is analyzed. It is pointed out that the currently calculated control rate of total annual runoff is actually the control rate of total annual precipitation. Hence, it is necessary to establish an internal relation with the gain factor of the response of the hydrological system, i. e. , the runoff coefficient. It also needs to be noted that the runoff coefficient is not a constant, but the time-varying nonlinearity of the combination of soil moisture, precipitation intensity, and the underlying surface. Additionally, the relationship between low impact development(LID)during sponge city construction and the improved control rate of total annual runoff are analyzed, in order to examine the conditions and risks of sea views in cities. Finally, it is suggested that the runoff coefficient nonlinearity, the differences in storage capacity between natural conditions and the conditions after urbanization, river and lake water system storage and land evapotranspiration, basin sponge regulation and control, and risk management should be strengthened on the hydrological basis of sponge city construction and planning. Some suggestions for future sponge city construction in China are put forward.