Native grass impacts water quality

    Native grasses play an important role in the world — one that is unseen. These grasses do it all underground with their roots. Native grasses with their deep roots have the capacity to filter water. Panicum virgatum (switchgrass) traps coarse sediment and plant nutrients from farm fields. Switchgrass has roots that go 9 to 10 feet deep with a massive root system only 12 inches underground.
    Think about all the impervious surfaces we have in our small towns. Roofs, roadways, parking lots, driveways, sidewalks, patios and tennis courts create runoff by not having a surface that allows permeability. The water runs off into storm drains, carrying substances including chemicals and oils from roadways and other toxic pollutants into rivers, streams and reservoirs.
    One plus side is if there are lots of parks and open grass areas with native grass, there are more opportunities to filter this runoff. The larger the area of grass in the landscape, the better filtered the water. It takes a while for the filtration to occur. This is not an instant process. Rather than having the water run off the cement and asphalt, which never gets the chance to run over a landscaped grass area, there are newer techniques to capture and filter water. Bioswales can be constructed, leading water to a storm drain, therefore increasing the filtration of many harmful substances.
     According to Ronald R. Schnabel in his article Improving Water Quality Using Native Grasses, “Native grasses improve water quality, both in limiting the source of pollutants and intercepting pollutants before they enter a water body.”
    Both native grasses and plants are used in bioswales. A swaled drainage course has gently sloped sites at less than 6 percent grade with native grass and/or native vegetation to stop silt and remove pollutants from the water before it gets to the storm drain. Both native grasses and native plants are used around detention basins for the same reason.
 

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