South
Holston Reservoir
Ecological
health rating
The overall ecological condition in South Holston Reservoir rated fair in 2010. 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 2010 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.
South
Holston Reservoir Ecological Health Ratings, 1994-2010
Click chart for raw
data.
The table below
shows the ratings for individual ecological health indicators at South
Holston in 2010. These ratings are briefly explained in the paragraphs
that follow.
|
Ecological
Health Indicators for
South Holston Reservoir, 2010
|
|
Monitoring
locations
|
Dissolved
oxygen
|
Chlorophyll
|
Fish
|
Bottom
life
|
Sediment
|
| Forebay |
|
|
|
|
|
| Mid-reservoir |
|
|
|
|
|
Dissolved oxygen
As in previous years, dissolved oxygen rated poor at both monitoring locations. Both locations experienced low dissolved oxygen concentrations (< 2 mg/L) August through October; however, a greater area of water was affected at the mid-reservoir location.
Chlorophyll
Chlorophyll concentrations were within the expected range at the forebay and mid-reservoir, rating good at both locations. 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.
Fish
The fish community rated at the upper end of the fair range at both monitoring locations. At both sites, 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.
Bottom life
Ratings for bottom life were fair at the forebay and poor at the mid-reservoir site. Bottom life at the forebay was slightly more diverse and abundant, but at both locations, the species collected were those able to tolerate poor conditions. Bottom life typically rates poor at both monitoring locations. However, the forebay also rated fair in 2008 and had not done so since 1994. The mid-reservoir’s only fair rating was in 2006.
Sediment
Sediment quality rated good at both monitoring locations. No PCBs or pesticides were detected and all metal concentrations were within the expected range. Sediment quality rated fair at the forebay in 2008 because the concentration of arsenic was slightly above expected background levels. Historically, sediment ratings have fluctuated between good and fair at both locations dependent on whether or not chlordane was detected. Chlordane is a pesticide previously used to control termites and crop pests, but it is no longer manufactured.
See definitions of
ecological health indicators and monitoring locations. |
|
Fish
consumption advisories
South Holston Reservoir - 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 Water Quality Division of Tennessee Department of Environment & Conservation’s web page. http://www.tn.gov/environment/water.shtml
Tennessee Valley Authority
