Rain Gardens Protect our Rivers and Lakes

November 3, 2019 lawanda Uncategorized

      When I first heard the term “rain garden” I thought it sounded so exotic, like something that would be located in the rain forest of the Amazon or perhaps the Pacific Northwest.  I soon learned that rain gardens can be installed anywhere it rains.  They are a way that all of us can improve the water quality of Wisconsin’s lakes, streams and groundwater by soaking up rain water from roofs, driveways and lawns. 

      Rain gardens increase the amount of water filtering into the ground rather than running off, which recharges groundwater and reduces the amount of pollutants washing into lakes and streams.  The EPA estimates that 35% of surface water pollution comes from runoff from homeowners’ yard care and chemical pollution from household activities.  A rain garden soaks up 30% more water than a lawn area of the same size and filters out pollutants in the process.

      Rain gardens are usually placed next to hard surfaces like sidewalks and driveways or at the end of drain spouts.  They are designed as shallow depressions three to eight inches deep with flat bottoms so that the water spreads out.  After an average rainfall, the garden will be wet for about 24 hours and then the water will soak in and the area will be dry.  Sometimes an outlet furrow is added so that excess water from major downpours drains away.

      After installation, a rain garden isn’t any more work than a regular garden and to the average onlooker, doesn’t appear any different.  Typically plants native to our area are used.  They need no pesticides or fertilizers and can tolerate alternating very wet and very dry conditions.  These native plants provide homes for birds, pollinators and other beneficial insects to a much higher degree than non-natives.

      Choosing plants for a rain garden is like designing any other garden.  Some people plant one or more shrubs in the middle surrounded by wildflowers.  To keep the garden looking neat, edges can be kept tidy with rocks, bricks or other edging.  Tall plants and grasses tend to flop over, so for a neat silhouette, stick with short species.

      Some weeding and watering may be necessary the first couple of years until plants become established.  Like any garden, plants can be moved, divided, or thinned depending on the whim of the gardener.

      The typical home rain garden is 100-300 square feet.  There are formulas for determining the proper size of a rain garden for the amount of runoff in a particular area, but a rain garden of any size does a lot of good.

      The rain garden should be at least ten feet from a home’s foundation so water doesn’t seep into the basement, and eight feet from a well, five feet from a septic system and one foot above bedrock or the high groundwater level.

      The DNR has an excellent publication that will help you plan the best size, location and plants for a rain garden: https://dnr.wi.gov/topic/Stormwater/documents/RainGardenManual.pdf.

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