September 22, 2011 at 8:45 a.m.
Rain gardens are shallow depressions that catch runoff from streets, driveways, downspouts, or other impervious surfaces and allow that water to infiltrate into the ground. Runoff water carries a variety of pollutants, garbage, sediment, chemicals, and excess nutrients to the nearest river, lake, or stream. Once in the water, nutrients feed algae that create algal blooms and can cause fish kills. Runoff also causes soil erosion.
Rain gardens are one option for reducing the effects of runoff. Water enters a rain garden and infiltrates into the ground. As water percolates down, garbage, sediment, and chemicals drop out of the water. Plants in the garden take up the nutrients while natural microorganisms in the soil break down chemicals. The water that leaves the rain garden has essentially been treated by natural processes and will recharge groundwater.
Rain gardens are designed to infiltrate water in less than 48 hours so there will not be standing water for an extended period of time. Mosquitoes require standing water for 5-7 days to breed. Native plants are most often chosen for rain gardens because they have extensive deep root systems that help infiltrate water and break up compacted soils. Native plants are also better adapted to our climate, require no fertilizer, and attract wildlife.
The SWCD received a grant for this project through the Clean Water Fund, which was adopted as part of the Clean Water Land & Legacy Amendment in 2008. The grant allowed the Library to create four rain gardens to capture runoff from the building and the two bordering streets. Nearly 900 perennial native flowers and grasses, over 70 shrubs, and 3 trees were planted to help infiltrate water and create habitat for birds and butterflies.
This project had a secondary goal of educating the public about different ways they can create landscaping that improves water quality in their own yards. There is a section of the garden planted in Prairie Dropseed, a native grass that is being used as a lawn replacement and does not get mowed. The south side of the building is planted entirely in a mix of native grasses. Throughout the rest of the garden are native flowers that have deep roots and beautiful flowers. These are three different ways that choosing the correct plants in strategic landscaping can improve water quality!
For technical assistance with planning and design of rain gardens, contact Mary Jo Youngbauer at the Chisago SWCD at 651-674-2333 or [email protected]. For more information about this or other SWCD projects, visit www.chisagoswcd.org.