The overall ecological condition in South Holston Reservoir rated fair in 2012. Historically, ecological health ratings have fluctuated within the poor and low-to-mid-fair range. In all years monitored, low ratings for two indicators — dissolved oxygen and bottom life — consistently reduce the reservoir’s overall health score. In 2012 and other years in which South Holston rated fair, several indicators scored at the upper end of their historical ranges.
TVA monitors two locations on South Holston Reservoir — the deep, still water near the dam called the forebay, and the middle part of the reservoir. Monitoring is usually done on a two-year cycle.
As in previous years, dissolved oxygen rated poor at both monitoring locations. Both locations experienced low dissolved oxygen concentrations (<2 mg/L) in the lower half of the water column during summer.
Chlorophyll rated good at the forebay but fair at the mid-reservoir because concentrations were slightly elevated. Chlorophyll has rated good at the forebay in all years except 1994, when it rated at the upper end of the fair range. Chlorophyll ratings have varied between good, fair and poor at the mid-reservoir location.
The fish community rated at the upper end of the fair range at both monitoring locations. Species diversity and catch rates were slightly lower than expected. Over time the fish assemblage has consistently rated good or a “high fair” at both locations.
Ratings for bottom life were “low fair” at the forebay and poor at the mid-reservoir. Bottom life at the forebay was slightly more abundant, but at both locations, the species collected were those able to tolerate poor conditions. Bottom life typically rates poor at the mid-reservoir and poor or at the low end of the fair range at the forebay.
Sediment quality rated good at both monitoring locations. No PCBs or pesticides were detected and all metal concentrations were within the expected range. Historically, sediment ratings have fluctuated between good and fair at both locations dependent on whether or not chlordane was detected. Chlordane, a pesticide previously used to control termites and crop pests, was last detected in the sediments of South Holston Reservoir in 2002. Sediment quality also rated fair at the forebay in 2008 because the concentration of arsenic was slightly above expected background levels.
TVA maintains a program to examine contaminants in fish fillets from TVA reservoirs and their major tributary streams on a rotational basis. The data collected from this program is distributed to the state officials who are responsible for placing or removing fish tissue consumption advisories on those bodies of water. For information on advisories currently in effect for South Holston Reservoir, visit the Tennessee Wildlife Resource Agency.