Hiwassee
Reservoir
Ecological
health rating
The overall ecological health condition for Hiwassee Reservoir rated fair in 2008, similar to all previous years monitored except 2006, when Hiwassee received a good rating. That was largely because bottom life received the highest score to date at both locations in 2006. In 2008, bottom life again received a poor rating at both locations. As in past years, low dissolved oxygen levels at the forebay reduced the reservoir’s overall score. Lower ratings for chlorophyll have been an issue in some years.
TVA monitors two locations on Hiwassee 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.
Hiwassee
Reservoir Ecological Health Ratings, 1994-2008
Click chart for raw
data.
The table below
shows the ratings for individual ecological health indicators at Hiwassee
in 2008. These ratings are briefly explained in the paragraphs that follow.
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Ecological
Health Indicators for
Hiwassee Reservoir, 2008
|
|
Monitoring
locations
|
Dissolved
oxygen
|
Chlorophyll
|
Fish
|
Bottom
life
|
Sediment
|
| Forebay |
|
|
|
|
|
| Mid-reservoir |
|
|
|
|
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Dissolved oxygen
Dissolved oxygen levels near Hiwassee Dam rated poor. Only a small percentage of the water column contained low dissolved oxygen, but a large section of the reservoir bottom was affected. Dissolved oxygen levels at the mid-reservoir sampling location have rated good since 2000, compared to fair in previous years.
Chlorophyll
Chlorophyll rated good at the forebay and poor at the mid-reservoir monitoring location. Chlorophyll last received a good rating at the forebay in 2001 (an off year, when not all ecological indicators were monitored) as compared to fair and poor ratings in recent years. Annual average chlorophyll concentrations have fluctuated through time at the forebay, with no specific trend of increasing or decreasing over time. Average chlorophyll concentrations have shown an overall increase at the mid-reservoir site since TVA began monitoring Hiwassee in 1991. Chlorophyll rated good or fair at the mid-reservoir from 1991 to 1996 and has rated poor since 1998.
Fish
The fish community rated good at the mid-reservoir location and at the upper end of the fair range at the forebay. The fish community typically rates good at both monitoring locations, but species diversity and catch rates were slightly lower than expected at the forebay in 2008.
Bottom life
Both locations received a poor rating. This is comparable to the poor to “low fair” ratings in most previous years with the exception of 2006, when both locations rated fair. The higher scores resulted from an increase in the density and diversity of organisms found in samples collected from the reservoir bottom.
Sediment
Sediment samples collected from the reservoir bottom were free of pesticides and PCBs, and concentrations of metals were within expected background levels, resulting in good ratings for sediment quality at both monitoring locations. Low levels of chlordane were detected at both locations in 1993 and 1998 sampling; no other contaminants have recorded concentrations above background levels.
See definitions of
ecological health indicators and monitoring locations.
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Fish
consumption advisories
Hiwassee 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 Hiwassee Reservoir, visit the Epidemiology Division of North Carolina Department of Health and Human Services’ web page. http://www.epi.state.nc.us/epi/fish/
Tennessee Valley Authority
