| dc.description.abstract | Traditional stormwater management does not mitigate groundwater depletion resulting from groundwater pumping and reduction in recharge. Infiltration practices, such as rain gardens, offer a potentially effective approach for addressing groundwater depletion. A rain garden is a landscaped garden in a shallow depression that receives the stormwater from nearby impervious surfaces, focusing recharge. We have developed a numerical model that can be applied in rain garden design and evaluation. Water flow through the rain garden soil is modelled over three layers - a root zone, a middle storage layer of high conductivity, and a subsoil lower layer. To continuously simulate recharge, runoff and evapotranspiration, the model couples the Richards Equation with a surface water balance. For the climate of southern Wisconsin, simulation results show that very high recharge rates are possible (twice the natural annual rates). A rain garden with an area of approximately 10% of the contributing impervious area maximizes groundwater recharge. We have installed an experimental rain garden to gather quantitative data on the water budget terms in a continuous fashion. Sensors were installed to measure the water input, garden ponding, soil moisture, and bottom drainage. To validate the Richards Equation model, we used data from three experiments resembling typical recharge events. The model results agree well with soil moisture data, but predict a higher recharge than measured (15 to 37% more). This could be due to intermediate storage in the system, insufficient characterization of initial conditions, or limitations of the 1-D model. Further study is recommended. | |
