The use of infiltration facilities represents an attractive opportunity to contribute to the recharge of groundwater and thus to minimise the interference of the natural water cycle. Stormwater infiltration returns surface flows to the subsurface and, thus, never aggravates flooding downstream. Additionally, a significant portion of the pollutant load of stormwater, which is normally directed to the receiving water, can be removed. If the soil through which water infiltrates contains any degree of clay or humus, the soil is a powerful filter that protects aquifers from contamination.
Some advantages of local rainwater infiltration are:
recharge of groundwater
preservation and/or enhancement of natural vegetation
reduction of pollution transported to the receiving waters
reduction of downstream flow peaks
reduction of basement flooding in combined sewer systems
reduction in the settlement of the surface in areas of groundwater depletion
smaller storm sewers at a lesser cost
In some cases rainwater infiltration may have following negative impacts (Urbonas & Stahre, 1993):
soils seal with time
some infiltration facilities may not receive proper maintenance
reliance on their operation may leave communities facing enormous capital costs in
the future, if these systems begin to fail
groundwater level may rise and cause basement flooding or damage to building
foundations