“(雨水)年径流总量控制率”辨析

Differentiation of “Volume Capture Ratio of Annual Rainfall”

"(雨水)年径流总量控制率"是近年来在中国海绵城市建设中出现的一个新名词,使用非常广泛,指导海绵城市建设中低影响开发(LID)地块的规划、设计、建设,并且是海绵城市建设验收和管理的核心指标。但是,由于其物理概念不明、专业语义模糊不清,在不同涉水行业中引起了混乱解读,妨碍了人们对海绵城市建设内涵的正确理解。其实,从学术的角度来说,年径流总量控制率就是"日雨量系列经验排序的百分位数"。"年径流总量控制率"往往与"将70%的降雨就地消纳和利用"这一海绵城市建设的总目标联系在一起,就全国范围的平均情况,与日雨量经验排序70%对应的设计日雨量仅相当于1年一遇的30%(0.304);而与85%对应的设计日雨量仅相当于1年一遇的50%(0.534)。由此看来,LID控制的仅是小雨部分,对解决初雨污染是起作用的,可以看作海绵城市建设的第一阶段;海绵城市建设的第二阶段应该是解决城市洪涝问题。建议把"(雨水)年径流总量控制率"改换成"(雨水)源头处理设计日雨量",更加专业、易懂、易推广。

The "volume capture ratio of annual rainfall" as a new term has emerged in Sponge City Construction in recent years. It has been applied widely in planning, design, construction of LID(low impact development) in Sponge City Construction, and been a key index during acceptance inspection and management of the LID construction as well. However, due to its unclear physical concept and indistinct connotation, it has caused confuse understandings within the water-related communities and hinders people from understanding of Sponge City Construction. In fact, from academic points of view, the Volume Capture Ratio of Annual Rainfall is simply the Percentile of Empirical Sorting of Dairy Rainfall Series, which is usually associated with the goal given to the Sponge City Construction, i.e. "to absorb and utilize 70% of the rainfall locally". Having had computation based on historical rainfall series, on average nationwide, the design daily rainfall amount is 30%(0.304) of the 1-year quantile corresponding to 70% percentile of the empirical sorting of daily rainfall series while 50%(0.534) of the 1-year quantile corresponding to 85% percentile of the empirical sorting of daily rainfall series. The Sponge City Construction should be phased into two: Phase I is focused on LID and Phase II is focused on mitigation of the urban flooding. We suggest that it is better to replace the term of "Volume Capture Ratio of Annual Rainfall" with "Design daily rainfall to basin watershed source treatment" for better understanding and application.