Tuesday, November 6, 2007 - 11:15 AM
167-9

Rain Gardens and Urban Water Quality.

Jacob Schneider, University of Wisconsin-Madison, 8001 Ritz Drive, Apt. 201, Madison, WI 53719-4581, John Stier, Horticulture, University of Wisconsin-Madison, 1575 Linden Dr., Madison, WI 53706, and Douglas Soldat, Soil Science, University of Wisconsin-Madison, 1525 Observatory Dr., Madison, WI 53706.

Urbanization has led to an increase in impervious surfaces that indirectly feed surface waters with potentially pollutant-laden water and reduce groundwater recharge. By using a landscaped garden in a shallow depression, a rain garden, that receives storm water from a rooftop, homeowners may be able to decrease the negative impacts that rooftops have on urban waters. This study investigated whether the presence of berms, type of vegetation, or combination of the two decreases runoff and increases groundwater recharge. Treatments included: 1) Kentucky bluegrass with a berm, 2) Kentucky bluegrass without a berm, 3) native mixture with a berm, and 4) native mixture without a berm, and they were planted in October 2005. Each plot had a separate rooftop, lysimeter, and runoff weir. Runoff and leachate volumes and samples were collected as appropriate. All samples were analyzed for NO3, NH4, total P, and dissolved P. Runoff samples were also analyzed for total suspended solids. After one year of data collection, both bermed treatments significantly reduced the amount of runoff and increased the amount of leachate when compared to both unbermed treatments. The unbermed native mixture treatments produced over two times more runoff than did the unbermed Kentucky bluegrass treatments. These results indicate that the presence of a berm appears to be the major determining factor behind rain garden effectiveness, regardless of vegetation type.