Chatuge Reservoir

Ecological health rating

Chatuge Reservoir rated at the low end of the fair range in 2008. Chatuge has rated either poor or at the low end of the fair range in most previous years. The fair ratings in 2008 and 2007 were primarily due to lower average chlorophyll concentrations.

Chatuge rated in the middle of the fair range in 2001 due to improved chlorophyll and dissolved oxygen conditions. Higher ratings in 1994 and 1996 were due to the fact that several indicators — chlorophyll, dissolved oxygen, and sediment quality — concurrently rated near the upper end of their historic ranges.

Weather conditions, particularly the timing and amount of rainfall, and the related changes in runoff have proved to be major factors in the variation of ecological health scores for Chatuge and many other reservoirs. In the forebay area of tributary reservoirs with long residence times (that is, where water sits for a relatively long period), dissolved oxygen and chlorophyll, the indicators most responsive to changes in weather conditions, tend to rate better during times of drought and worse during periods of normal or higher rainfall and runoff. This is because fewer nutrients and less organic material are washed into the reservoir when rainfall and runoff are low, and that tends to produce lower chlorophyll concentrations and less oxygen demand to decompose organic materials.

TVA has monitored two locations on Chatuge Reservoir — the deep, still water near the dam and the Shooting Creek location — annually since 1998.

Chatuge Reservoir Ecological Health Ratings, 1994-2008

Click chart for raw data.

The table below shows the ratings for individual ecological health indicators at Chatuge in 2008. These ratings are briefly explained in the paragraphs that follow.

Monitoring locations	Dissolved oxygen	Chlorophyll	Fish	Bottom life	Sediment
Ecological Health Indicators at Chatuge Reservoir, 2008
Forebay	Poor	Good	Fair	Good	Fair
Shooting Creek	Poor	Good	Fair	Fair	Poor
Dissolved oxygen Dissolved oxygen rated poor at both monitoring locations due to low concentrations in the lower water column from August through October. Ratings have fluctuated between fair and poor in response to the timing and amount of rainfall. Chlorophyll Chlorophyll rated good at both monitoring locations. Similar to dissolved oxygen, chlorophyll ratings have fluctuated between good, fair, and poor. Fish The fish community rated fair at both monitoring locations, the same as in most previous years. Catch rates were lower than expected, and species diversity was fair. Bottom life Bottom life rated at the low end of the good range at the forebay and at the low end of the fair range at the Shooting Creek location. Bottom life has rated fair or poor in prior years because relatively few organisms were found in samples collected from the reservoir bottom, and most are species able to tolerate poor conditions. The good rating at the forebay in 2008 was attributable to the collection of a greater variety of organisms, suggesting a subtle improvement in bottom life at this location. However, tolerant species still comprise the largest percentage of the community at both the forebay and the Shooting Creek locations. Sediment Sediment quality rated fair at the forebay because of slightly elevated concentrations of copper. The Shooting Creek location rated poor due to elevated concentrations of chromium, copper, and nickel. Elevated concentrations of one or more of these metals are usually detected in the sediments of Chatuge. See definitions of ecological health indicators and monitoring locations.

Fish consumption advisories

The state of Georgia issued a fish consumption advisory for spotted bass in the Georgia portion of Chatuge Reservoir because of mercury contamination. The state advises people not to eat more than one meal a week of spotted bass between 12 and 16 inches in length.

TVA collected channel catfish and largemouth bass from the reservoir for tissue analysis in the autumn of 2004. The results, which were provided to state agencies in Georgia and North Carolina, were similar to those of previous years. TVA will collect fish from Chatuge again in the autumn of 2008.