Minnesota’s most notable attraction is its ever-famous waterways. But with each passing year, we grow closer to losing our north woods heritage. Water pollution threatens the delicate ecological balance of our waterways: high levels of chemicals, nutrients, and sediment harm vegetation, kill wildlife, foul drinking water, and destroy pristine recreational areas.
Rain Gardens Reduce Runoff, a Major Source of Water Pollution
Up to 70 percent of harmful pollutants are introduced by storm water runoff: unfiltered water that reaches waterways by flowing across impervious surfaces: roads, parking lots, driveways, and roofs. Runoff deposits pollutants – via storm drains and sewers into our lakes and streams. Lawn clippings and leaves are also washed into our waterways, reducing oxygen levels and ultimately suffocating fish and other aquatic species. Water that comes off an asphalt roof onto an oil-stained driveway will flow across an over-fertilized lawn straight into creeks, rivers, and lakes.
How Rain Gardens Work
It just so happens that soil acts as a superb filtering system. Basically, a rain garden slows water down so it can be filtered by the soil. Think of a rain garden as a scaled-down version of a wetland area. Native plant material, a soil mixture that is optimal for filtration and absorption, and proper grading create a system that facilitates water uptake into the soil.
Rain Garden Features
The features of a rain garden include:
- a shallow basin with gentle side slopes (usually four to eight inches deep);
- soil that allows infiltration;
- and moisture-tolerant plants with deep roots to trap sediment.
The basin temporarily traps the water, allowing the soil and plant material to work their cleansing magic. Soil should be porous enough to absorb water within 48 hours. This keeps the garden from becoming a breeding ground for mosquitoes. Native plants work best in rain gardens because they are uniquely adapted to live through extremes of moisture and temperature. And their long roots are helpful for water infiltration.
A rain garden can be large or small, and almost any size or shape. Even a small rain garden can make a difference. Rain gardens require very little maintenance and provide attractive habitat for butterflies and birds. Annual cleanup and occasional weeding are all that’s required.
Choosing the Right Location for your Rain Garden
In order to do its work, a rain garden should be strategically located to intercept water that flows from gutters and downspouts and across paved surfaces such as driveways and walkways. A rain garden located under a downspout can capture thousands of gallons of water annually. Rain gardens are commonly located near alleys and driveways, in the low areas between houses, and in places where pools and puddles naturally occur. Ideally, water should be captured as close as possible to where it falls. Runoff can be re-directed along channels. You can also use a rain barrel and garden hose to direct runoff into a rain garden.
Start Your Rain Garden Today
For help designing and building a rain garden or green space that is beneficial for the environment, contact us, or visit these helpful rain garden links:
Plotting to Infiltrate? Try Rain Gardens University of Minnesota Extension
Rainwater Gardens City of Maplewood
Create a Garden raingardens.org
Rain Gardens Gain Popularity Metropolitan Council Clean Water
Plants for Stormwater Design Minnesota Pollution Control Agency
|
|
Water quality protection. Proper landscaping reduces nitrate leaching from the soil into the water supply and reduces surface water runoff, keeping phosphorus, and other pollutants out of our waterways.
Reduced soil erosion. A dense cover of plants and mulch holds soil in place, keeping sediment out of lakes, streams, storm drains and roads.
Improved air quality. Trees, shrubs, and turf remove smoke, dust and other pollutants from the air. One tree can remove 26 pounds of carbon dioxide from the atmosphere annually, equaling 11,000 miles of car emissions.
Lower summer air temperatures. Trees shading homes can reduce attic temperatures as much as 40 degrees. According to the EPA, urban forests reduce urban air temperatures significantly by shading heat sinks such as buildings and concrete, and returning humidity to the air through evaporative cooling.
Natural resource conservation. By using trees to modify temperatures, the amount of fossil fuels used for cooling and heating is reduced. Properly placed shade trees reduce house temperatures in the summer, allowing air conditioning units to run 2 to 4 percent more efficiently, but allowing the sun to warm the house in the winter.
SOURCE: Project EverGreen Environmental Fact Sheet, www.projectevergreen.com
|
