South
Holston Reservoir
Ecological
health rating
The overall ecological condition in South Holston Reservoir rated at the low end of the fair range in 2008. Conditions were similar to most previous years. Low ratings for two indicators — dissolved oxygen and bottom life — consistently reduce the reservoir’s overall health score.
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, 1994-2008
Click chart for raw
data.
The table below
shows the ratings for individual ecological health indicators at South
Holston in 2008. These ratings are briefly explained in the paragraphs
that follow.
|
Ecological
Health Indicators for
South Holston Reservoir, 2008
|
|
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. Low dissolved oxygen concentrations occurred in the lower water column from June through October at both monitoring locations.
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, but average concentrations have shown a general trend of increasing.
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. This was the forebay’s first year to receive a fair rating since 1994. The mid-reservoir rated fair in 2006.
Sediment
Sediment quality rated fair at the forebay and good at the mid-reservoir site. No PCBs or pesticides were detected at either site, and all metal concentrations were within the expected range at the mid-reservoir site. Sediment quality rated fair at the forebay 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
There are no fish
consumption advisories on South Holston Reservoir. TVA collected
channel catfish and largemouth bass from the reservoir for tissue analysis
in
the autumn of 2004. All contaminant levels were either below detectable
levels or below the levels used by the state of Tennessee to issue
fish
consumption advisories. TVA will analyze fish from South Holston again
in the autumn of 2008.
Tennessee Valley Authority
