The ecological health condition of Chatuge Reservoir rated poor in 2012. Chatuge has rated either poor or at the low end of the fair range in most previous years. The mid-fair rating in 2010 was largely because of an improvement in bottom life, first observed in 2008, and improved dissolved oxygen conditions.
Chatuge also rated in the middle of the fair range in 2001 due to improved chlorophyll and dissolved oxygen conditions. Higher ecological health 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 higher than normal 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 monitors two locations on Chatuge Reservoir—the deep, still water near the dam and the Shooting Creek location.
Dissolved oxygen rated poor at both monitoring locations due to low concentrations (<2 mg/L) 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 concentrations were within the expected range, resulting in a good rating at both monitoring locations. Similar to dissolved oxygen, chlorophyll ratings have fluctuated between good, fair and poor.
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 rated at the low end of the fair range at the forebay and poor at the Shooting Creek location. Bottom life has rated fair or poor at both locations most years because relatively few organisms are found in the samples, and most are species able to tolerate poor conditions. The higher ratings (good) at the forebay in 2008 and 2010 were attributable to the collection of a greater variety of organisms, suggesting there was a subtle improvement in bottom life at this location those years. However, tolerant species have continually comprised the largest percentage of the community at both locations.
Sediment quality rated good at the both locations. No PCBs or pesticides were detected, and concentrations of metals were within expected background levels. Sediment quality typically rates fair at the forebay and poor at the Shooting Creek location because elevated concentrations of one or more metals (chromium, copper and/or nickel) are usually detected in the sediments.
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 Chatuge Reservoir, visit the Environmental Protection Division of Georgia Department of Natural Resources.