Wednesday, July 2, 2014

Rain Gardens


Chadron State College rain garden, planted June 28, 2014
Christina Hoyt

        Water conservation can be as simple as directing downspouts to planted areas, placing small areas of grasses or other deep-rooted plants on slopes or areas off downspouts, decreasing paved areas, using permeable pavers and installing rain barrels. A growing awareness of the pollutants in rainwater, however, has led to the use of rain gardens—depressions planted with native or adapted plants that help absorb excess water and filter out excess nutrients before entering the groundwater system. When placed to receive runoff from roofs, downspouts and paved areas, they can capture and filter as much as 90 percent of common pollutants.

        Plants for these areas need to tolerate extremes since there will be periods of standing water when the soil is saturated and also very dry periods. They are meant to drain within 24-48 hours, a rate that will depend on the amount of runoff the area receives, quality of the soil, plant absorption and the depth of the depression. Recommended depth is about 8” since deeper areas are less likely to drain well, difficult to plant effectively and soil and mulch are likely to erode. Gravel or rocks can be placed where water enters and exits to help slow the water flow, spread it out and prevent erosion.

Lincoln Fireworks rain garden, planted in 2009.
        Some of the plants recommended for rain garden areas in full sun are deep-rooted native and ornamental grasses, black-eyed Susan, goldenrod, iris, butterfly milkweed and gayfeather.

        They can also be planted in part shade with plants like: astilbe, lady’s mantle, iris, Korean reedgrass, sedges, aster, coneflower, turtlehead, Joe Pye-plant, germander, hibiscus, etc.

        Fast facts (more at arboretum.unl.edu and  water.unl.edu): 

  • Stormwater runoff is the primary water quality problem in America
  • In cities, about 50 percent of rain water goes into storm sewers
  • Runoff from a 1” rain may exceed 5,000 gallons—even from a 1,500 square foot house on a small lot
  • More than 50 percent of outdoor water usage goes into watering lawns and gardens
  • On a dry summer day in Lincoln, lawns alone may absorb more than 50 million gallons of water per day from the Platte River

        There are a wide range of regional resources on water conservation and rain gardens at water.unl.edu and lincoln.ne.gov (keyword: rain gardens). Nebraska Statewide Arboretum has a “Waterwise Landscapes” publication and there is a series of stormwater management NebGuidesfrom the University of Nebraska: Rain Garden Design for Homeowners, Installing Rain Gardens in Your Yard and  Plant Selection for Rain Gardens in Nebraska.

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