The ecological health condition of Chatuge Reservoir rated “poor” in 2018. Chatuge has rated either “poor” or at the low end of the “fair” range most 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. The higher ecological health scores in 1994 and 1996 were due to the fact that several indicators —dissolved oxygen, chlorophyll, 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 proven 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 (time that water spends in the reservoir), dissolved oxygen and chlorophyll, the indicators most responsive to changes in weather conditions, tend to rate better during periods 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.
The ecological health of Chatuge Reservoir has been monitored using the same methodology since 1994. Ecological health evaluations focus on five indicators: dissolved oxygen, chlorophyll, sediment quality, benthic macroinvertebrate community (bottom life), and the fish assemblage. TVA monitors two locations on Chatuge Reservoir: Hiwassee River Mile 122.0 and Shooting Creek Mile 1.5. Both are located in the forebay — the deep, still water near the dam.
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>72 = Good
59-72 = Fair
<59 = Poor
|Forebay - Hiwassee River||Poor||Good||Fair||Poor||Fair|
|Forebay - Shooting Creek||Poor||Good||Fair||Fair||Poor|
Dissolved oxygen rated “poor” at both monitoring locations due to low concentrations (<2 mg/L) in the lower water column during August and October. Ratings have fluctuated between “fair” and “poor” in response to the timing and amount of rainfall. Low dissolved oxygen concentrations are not uncommon in the lower water column of deep, tributary reservoirs with long residence times. Although oxygen concentrations in the upper water column remain adequate for aquatic life, the animals that live on or in the sediments can be exposed to low concentrations.
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”; however, chlorophyll typically rates “good” or at the upper end of the “fair” range. It should be noted that chlorophyll concentrations in Chatuge Reservoir are assessed relative to expectations for the Blue Ridge Ecoregion, which has naturally low nutrient concentrations. Therefore, chlorophyll concentrations are expected to be much lower in Chatuge than in other Tennessee Valley reservoirs located outside the Blue Ridge Ecoregion.
The fish community rated “fair” at both monitoring locations, the same as in most previous years. Characteristics of the fish communities (e.g., fish abundance, species richness and composition) were similar to long-term averages for the respective sampling locations. A total of twenty-two different species of fish were observed, with composition being dominated by a few species such as bluegill, spotted bass, and redbreast sunfish.
Bottom life rated “fair” at the Shooting Creek monitoring location and “poor” at the Hiwassee River 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 a wide range of conditions. The higher ratings (“good”) at the Hiwassee River location 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 made up the largest percentage of the community at both locations.
Sediment quality rated “fair” at the Hiwassee River monitoring location and “poor” at the Shooting Creek location. Concentrations of chromium and nickel were above suggested background levels at both locations, and copper was above suggested background levels at the Shooting Creek location. No PCBs or pesticides were detected. Elevated concentrations of one or more metals (copper, chromium and/or nickel) are usually detected in the sediments of Chatuge. These metals naturally occur in soils but can also originate from many sources. Their concentrations in sediments deposited in the reservoir are generally near—slightly above or slightly below—suggested background levels.
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.