Field Evaluation of Rain Gardens as a Method for Enhancing Groundwater Recharge

Background/Need: In urbanized areas of Wisconsin that rely on groundwater as the primary source of water, groundwater withdrawals significantly exceed groundwater recharge rates. This can lead to environmental degradation, as it reduces the discharge of groundwater to springs, wetlands, streams, and lakes and their
associated ecosystems. Rain gardens, sunken gardens that receive stormwater runoff, appear to offer a solution to groundwater loss. In a previous research project, the PI has used a numerical model to demonstrate that a rain garden with area equal to 10% of the connected pervious area can double the local groundwater recharge rate. The explanation of this surprising result is that focusing of runoff to a small, highly pervious area greatly reduces losses to evapotranspiration.

Objectives: Before rain gardens can be widely implemented, they should be tested through carefully designed demonstration projects. The purpose of the proposed project was to construct an experimental rain garden for use in evaluating rain garden performance.