雨水花园对暴雨径流的削减效果

雨水花园能够有效地蓄渗雨水径流、降低城市发展对水环境的不利影响.根据在西安市开展的一项连续4年对雨水花园入流与出流水文过程的监测研究,分析了雨水花园对暴雨径流的削减效果,并根据花园内土壤入渗率及颗粒组分随时间的变化,讨论了雨水花园运行效果的可持续性.结果显示:蓄水深度为15 cm,汇流比为20:1的试验用雨水花园,在4年监测的28场降雨中,仅有4场暴雨径流汇入雨水花园后发生溢流,且溢流量很小;试验期内,有2年未发生溢流,雨水径流全部入渗;最多的1年发生溢流3次,但年径流削减率仍高达96.8%;导致雨水花园发生溢流的均为短历时高强度暴雨.研究中还发现,雨水花园土壤入渗率在4年运行期内没有显著变化,一直稳定在2.4 m/d左右,花园内表层土壤砂粒含量由7.36%增加到20.55%,而粉粒和黏粒的含量则相应降低.可见,研究区雨水花园能够显著减少暴雨径流,且入渗性能稳定,具有良好的应用前景.

Effect of rain gardens on storm runoff reduction

Rain gardens can be used effectively for retaining stormwater runoff and mitigating the negative impact of urban development on the aquatic environment. By monitoring the inflow and outflow processes of a rain garden over four years in Xi'an, China, this paper presents a study on the effect of a rain garden on storm runoff reduction; the sustainability of the rain garden operation was examined on the basis of soil sampling for particle size analysis and onsite measurements of infiltration capacity. The results showed that, for the experimental rain garden constructed with ponding depth of 15 cm and flow catchment area ratio of 20:1, only 4 storm events produced overflow from the rain garden out of the 28 monitored events, and the overflow volumes were generally small; there were no overflow occurred in two years, all inflow infiltrated in the rain garden; there was maximum 3 overflow events in one year, but the runoff reduction rate was as high as 96.8％; the storms that caused the rain garden overflow were all high intensity and short duration events. The onsite infiltration measurements showed no significant change in the infiltration capacity over the four years, the rain garden infiltration capacity was maintained at 2.400 m/d. The soil particle size analysis showed that, sand content at the surface layer of the rain garden increased from 7.36％ to 20.55％, while the silt and clay contents decreased accordingly. These results indicate that rain gardens can reduce storm runoff significantly, and the stable infiltration capacity entitles them a promising future in the study area. Findings from this research may provide theoretical basis and technical support for the sponge city construction in China.