by Lee Boggs
In our continued effort to preserve and protect the Radnor Lake State Natural Area, Friends of Radnor Lake initiated an extensive eight-year water quality assessment with supporting funding from a CSX railroad environmental education grant. The need for this study was related to the increasing suburban development in the Radnor Lake watershed, public concern for lake health and the need to promote public awareness of potential threats to Radnor Lake, including the impending Piedmont Gas pipeline construction.
The study was conducted to determine the quality of the water in Radnor Lake and its feeder streams and to determine its overall health. Radnor Lake is an 85-acre lake, with the deepest point being approximately 50 feet with an average depth of 12-14 feet. Since the lake is the “crown jewel” of the Radnor Lake State Natural Area, FORL wanted to develop a solid baseline of data with which to focus its efforts to preserve this sensitive natural watershed.
FORL contracted with Chris Van Loon, a graduate student at Vanderbilt, to conduct the study. Supporting this effort was the steering committee composed of Steve Ward, park manager; Lee Boggs, FORL board member; Dr. Oliver Yates, Jr., retired chairman of Lipscomb University Biology Department; and Scott Hall, manager of ecotoxicology at Environ International Corporation. Park rangers and students from Lipscomb, Middle Tennessee State and Vanderbilt Universities also contributed.
In 2005, the initial study was performed on the lake and five primary feeder streams in the winter, spring, summer and fall, followed by an annual sampling and analysis until its completion in 2011. Five primary water characteristics were tested: nitrates, phosphates, dissolved oxygen, temperature and pH (alkalinity), all recognized by water-quality specialists as the leading determinates of water quality for a lake and watershed like Radnor. Fecal coliform was also tested to determine if there was any contamination in the lake from septic tanks and/or broken sewer lines in the watershed.
All of the analyses show the quality of the water to be supportive of rare plants, aquatic organisms and upland wildlife, all strong indices of a healthy lake. The Tennessee Department of Environment and Conservation water quality standards were used, and all five characteristics were generally good. However, there was an eight-fold increase in nitrate concentrations from 2005 to 2011 and concentrations above recommended ranges for phosphates in three of the creeks downstream of neighboring subdivisions. Dissolved oxygen levels were strong in the feeder streams and good in the lake itself.
Temperature readings averaged well below the 86.9 degree Fahrenheit threshold, and pH (alkalinity) levels were within range. Fecal coliform concentrations were below the 100 cfu/100 mL threshold.
While the quality of the water in Radnor Lake and from the feeder streams is relatively good, there are areas of concern. Nitrates and phosphates contribute to eutrophication, an exponential growth of plant life and algae that die off and create high volumes of dead organic matter that consumes dissolved oxygen in the water. Insufficient dissolved oxygen levels are stressful to and can kill off plant and aquatic organisms. The algae covering Big South Pond, located south of Otter Creek Road near the eastern side of the lake, is a visual example of eutrophication. Future concentrations at current levels will be detrimental to water quality and the overall health of the lake.
The current condition of water quality in the lake can be compared to a person’s health. For example, while a person’s annual physical exam may show good general health, there may be negative contributors such as increased levels of cholesterol and blood pressure above recommended ranges. This is the same for the overall health of the water in Radnor Lake. Certain feeder streams indicate high concentrations of nitrate and phosphate. In both instances the negative contributors need to be dealt with now before they damage overall good health. Just as specific causes of health issues are not always clear, direct links between individual or community behavior and water quality are not exactly concluded from this study. However, these data do suggest potential human-related influences on certain areas of the watershed based on readings falling outside of safe range.
Recommendations for action include continued monitoring and evaluation of water characteristics, identification of sources of contaminants (nitrates and phosphates), initiation of efforts to reduce and/or remove contaminants, continued work with the City of Oak Hill on land-use regulations and controls to prevent contamination, initiation of a water quality education campaign, help given to neighboring home-owner associations to reduce nitrate and phosphate discharges to feeder streams and continued focus on acquisition of land in the watershed to protect the quality of water in Radnor Lake. FORL will continue focusing on its mission to help accomplish water quality protection, and park visitors and neighbors can help by avoiding overuse of fertilizers, encouraging others to do the same and supporting environmental education programs at Radnor Lake.