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Ground Water and Ecosystems Restoration Research |  |
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GWERD Research on Stream and Riparian Restoration to Benefit Water Quality
Stream channels and corridors (riparian zones) are sometimes restored and reconstructed to improve habitat for fish and to stabilize banks against erosion and incision (photo, upper left). Such efforts also may serve to benefit water quality, however, the effectiveness of restoration for improving surface or ground water quality have not been thoroughly assessed. The same techniques used to improve fish habitat or stabilize stream banks may also serve to remove or reduce nutrients that have detrimental effects on human health and aquatic life. For example, nitrogen, which is required in small amounts for growth of living organisms, can pose health risks when concentrations are high. Excess nitrogen enters streams from fertilizer runoff, animal wastes, sewer lines, and atmospheric deposition of nitrous oxides from fossil fuel combustion such as from automobile exhaust (figure, middle left). Ecological restoration may enhance the ability of a stream to naturally remove nitrogen through denitrification, a process performed naturally by microbes in the water and subsurface. If certain restoration techniques were found to support the conditions necessary for denitrification (e.g. organic material available to microbes, low oxygen conditions), then restoration may be a cost effective means of improving water quality and thus, maintaining human and ecological health. The Groundwater and Ecosystems Restoration Division (GWERD) of the EPA in Ada, OK is examining the effects of stream restoration on water quality in Baltimore, MD where a degraded urban stream called Minebank Run will be restored to stabilize stream banks and reduce further channel erosion (photo, upper right). GWERD scientists and researchers from US Geological Survey and the Institute of Ecosystem Studies are assessing the changes in the structure and ecological function of Minebank Run both before after the restoration. The restoration and reconstruction techniques will include reshaping stream banks to reduce the slope (figure, middle right), stream bank reinforcement, reconstructing stream meanders and riffle zones, and re-establishing riparian plant communities. Nitrogen concentration is being tracked over time and tests of denitrification rate are being monitored throughout the stream (photo, lower left). This information will provide an indication of the change in the ability of the stream to naturally reduce excess nitrogen. Other water quality parameters such as organic matter movement, sediment load, erosion rates, phosphorous, mercury, and road salts are being measured. The objectives of this study are to assess the ecosystem benefits of restoration and to identify stream restoration methods that enhance nitrogen control or otherwise improve water quality. When such methods are identified, EPA can develop ecologically-based guidelines for stream restoration and share this information with land managers who have a need and desire to restore the ecological health of streams and riparian zones as well as improve water quality for residents in the watershed (photo, lower right).
Recent Hightlights Field Project: "The effects of ecosystem restoration on nitrogen processing in an urban mid-Atlantic Piedmont stream"; (contact: mayer.paul@epa.gov) Field Project: Ground Water and Surface Water Interactions Along Riparian Corridors in the Great Basin;(contact: jewett.david@epa.gov)
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