Tennessee Valley Authority
Nickajack Reservoir
Ecological health rating
As in previous years, Nickajack Reservoir rated good in 2007. The ecological health score for Nickajack has consistently been among the highest of all the reservoirs monitored by TVA. Nickajack is a small, narrow reservoir with a short retention time. It usually takes only three or four days for water to flow through the reservoir, which helps keep the water mixed, preventing it from stratifying (separating into layers of different temperatures) during the summer. This allows oxygen in the lower water column to be replenished and limits algal growth, which causes elevated chlorophyll concentrations.
TVA monitors two locations on Nickajack Reservoir—the deep, still water near the dam, called the forebay, and the riverlike area at the extreme upper end of the reservoir, called the inflow—usually on a two-year cycle.
Nickajack Reservoir Ecological Health Ratings, 1994-2007
Click chart for raw data.
The table below shows the ratings for individual ecological health indicators at Nickajack in 2007. These ratings are briefly explained in the paragraphs that follow.
|
||||||||||||||||||||||||||||||
Fish consumption advisories
The state of Tennessee has issued a precautionary fish consumption advisory for channel catfish from Nickajack Reservoir because of PCB contamination. A precautionary advisory means that pregnant women, nursing mothers, and children should not eat the contaminated fish. All others should limit their consumption of the named species to no more than one meal per month. Additionally, the state has issued an advisory that fish from Chattanooga Creek, a tributary stream of Nickajack, should not be eaten because of elevated PCB and chlordane levels.
TVA collected channel catfish, striped bass, and largemouth bass from Nickajack Reservoir for tissue analysis in fall 2005. The results, which were similar to those of previous years, will be provided to state agencies in Tennessee. TVA will analyze fish from Nickajack Reservoir again in autumn 2007.
