Signs of Health Returning to Restored 'SWAMP' in Duke Forest
Tests show the restored 14-acre Stream and Wetland Assessment Management Park is boosting biodiversity and helping reduce nitrate pollution in water downstream
Three years after undergoing a massive restoration, a once heavily eroded and polluted 14-acre stretch of wetlands along a Durham creek is showing signs of renewed health and helping to reduce nitrate pollution in the Triangle's drinking water supply.
"The changes we're observing -- not only in the restored stream-wetland-lake complex itself but also in water quality downstream from it -- are extremely encouraging," said Curtis J. Richardson, director of the Duke University Wetland Center and professor of resource ecology at the Nicholas School of the Environment and Earth Sciences.
Duke University officials dedicated the Stream and Wetland Assessment Management Park (SWAMP) on Wednesday, May 2. SWAMP is located along a stretch of Sandy Creek in Duke Forest, near the Al Buehler Cross Country Trail and just a stone's throw across N.C. 751 from Duke's West Campus.
The site is designed to help protect the Triangle's drinking water supply by controlling contaminant-laden storm runoff from Duke's campus and 1,200 surrounding acres of Durham. It also functions as an outdoor teaching and research laboratory for undergraduate and graduate students in environmental studies and engineering.
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Scientists and students at the Duke University Wetland Center have worked for more than three years on the first three phases of the restoration. They have re-contoured and replanted Sandy Creek's formerly silt-clogged streambed and banks, restored a riparian wetland along the floodplain, built a wetland and built a new storm water reservoir and earthen dam to replace an old dam.
Storm runoff containing heavy concentrations of sediment, nitrogen, phosphorus and other urban pollutants drains into Sandy Creek. The stream is a tributary of New Hope Creek, which meets state pollution standards when it enters northern Durham County, but often has been in violation by the time it left southern Durham County bound for Jordan Lake, part of the Triangle's drinking water supply.
Tests conducted prior to SWAMP's restoration and one year after its completion show that nitrate pollution downstream has been reduced substantially, Richardson said.
"Rapid declines in nitrate concentrations between testing stations immediately above and below the site suggest significant ecosystem metabolism is taking place within the restored stream-wetland complex," he said. "It is once again functioning as a wetland should."
Nitrate levels at testing stations along the creek have been well below the North Carolina water quality standard of 10 milligrams per liter every month since restoration was completed. Prior to restoration, nitrate levels in the creek exceeded state limits four times during the test period of July 2003 to July 2004.
Species richness in the restored ecosystem also is improving. Field surveys done prior to and after restoration show that the stream today provides habitat for two new orders and five new species of aquatic insects, with a total of 89 species now found there.
"The return of macroinvertibrates is one of the first signs that you've done the job right," Richardson said.
In addition to its roles as a pollution buffer and wildlife habitat, the restored ecosystem serves as an outdoor classroom, training center and field laboratory.
Hundreds of students from the Nicholas School, Duke's Pratt School of Engineering, the University of North Carolina at Chapel Hill, the North Carolina School of Science and Mathematics and other area universities and schools, as well as staff members from the North Carolina Museum of Life and Science, attend classes and take part in hands-on training sessions there.
Researchers from numerous local institutions use the site to conduct studies on biological diversity, hydrology, water quality, mosquito control, invasive plant species and other environmental issues.
"What we learn here will benefit wetland and stream restoration projects nationwide," Richardson said. "SWAMP provides a unique opportunity to train students on real-world restoration techniques and modern hydrologic modeling approaches, as well as basic principles of stream, lake and wetland ecology."
Signs along the Al Buehler Trail, which crosses and then parallels a section of SWAMP, educate the public about the role wetlands play in environmental health. Boardwalks provide opportunities to view the plants and wildlife.
Plans call for restoring a second tributary of Sandy Creek, upstream from the current project, beginning later this year. After that, Richardson hopes to investigate the possibility of expanding the project to two additional tributaries, both of which have headwaters near a Durhamelementary school, so that the entire Upper Sandy Creekwatershed eventually is included.
"Our goal is to 'green' the entire stream-wetland system on campus and aid the City of Durham and Durham County in improving water quality," Richardson said.