雨水花园集中入渗对地下水水位与水质的影响

作为低影响开发（Low Impact Developmet， LID）措施之一，城市雨水花园集中入渗雨水径流可增加对城区地下水的补给。根据一现场监测试验，研究了长期（监测期3年）及短期（降雨3天内）雨水花园入渗点及对照点地下水位与水质的变化，分析了集中入渗的效果和影响范围。结果表明:① 雨水花园对入渗区地下水位产生了显著影响（α=0.01）；② 氨氮（NH₄-N）在3年及雨后3日的观测值均显著小于对照值；总氮（TN）指标在短期增加显著，长期均值增加不显著。③ 硝态氮（NO₃-N）浓度在降雨后有所升高，但不显著，几个观测点浓度有增有减；总磷（TP）浓度的短期值和长期均值有增有减。对于类似研究区地下水位在2~3 m的情况，集中入渗雨水径流可有效补给地下水，对氮素影响明显，对磷影响有限。

Influences of focused recharge from rain gardens on groundwater level and water quality

As a low impact development (LID) practice, rain gardens may increase groundwater recharge in urban areas through focused infiltration of the storm runoff. This paper explored the impact of focused recharge through rain gardens on groundwater level and water quality based on a field monitoring study; the observed groundwater level and water quality metrics between the recharge point and a reference well were compared for both long-term (3 years) and short-term (3 days after the rain) periods. The results showed that the groundwater level in the rain garden recharge area was significantly higher the reference point (confidence level α=0.01, same hereafter). The groundwater quality observations showed that, the average concentrations of NH₄-N at the recharge point were significantly lower than that at the reference point for both long-term and short-term values; the TN concentrations increased in 3 days after storms, but the average concentration in 3 years did not increase significantly; the NO₃-N concentrations at the recharge points slightly increased, but not significantly different from the reference point. The TP concentrations was observed with both increased and decreased values during the long-term and the short-term periods. Findings from this research indicate that rain gardens may produce effective recharge to groundwater, limited influence on P, and significant influence on nitrogen concentration in groundwater for areas that water table depth is greater than 2-3 m.