The ecological health of Nottely Reservoir rated “poor” in 2017. Nottely typically rates “poor” due to low ratings for dissolved oxygen, chlorophyll, and bottom life. Ratings for these indicators improved in 2001, rating at the upper end of their historic range and resulting in a higher overall health rating of “fair”. However, subsequent monitoring indicated that the improvements were only a temporary result of the unusual rainfall and reservoir flow patterns in 2001.
The ecological health of Nottely 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 Nottely Reservoir — the deep, still water near the dam, called the forebay (Nottely River Mile 23.5), and the middle part of the reservoir, called the mid-reservoir (Nottely River Mile 31.0).
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>72 = Good
59-72 = Fair
<59 = Poor
Dissolved oxygen rated “poor” at both the forebay and mid-reservoir monitoring locations. A large proportion of the lower water column contained low dissolved oxygen concentrations during a portion of summer and autumn at these locations. This is similar to all previous years, except 2001 when oxygen concentrations were significantly higher at the forebay and rated “good”, and 2005 when significant rain events in late summer helped replenish oxygen in the upper reaches of the reservoir resulting in a “fair” rating for the mid-reservoir location. Although dissolved oxygen typically rates “poor”, the extent and duration of low dissolved oxygen has varied in response to the timing and amount of rainfall each year.
As part of TVA’s Reservoir Release Improvement Program in the late 1990s, TVA installed aeration equipment (turbine air injection and forebay oxygen injection) at Nottely Dam to improve the quality of water released from the dam.
Chlorophyll rated “good” at the forebay and “poor” at the mid-reservoir. A “poor” rating is typical at the mid-reservoir location, but ratings at the forebay have varied between “good”, “fair”, and “poor”. As with dissolved oxygen, chlorophyll concentrations have varied in response to the timing and amount of rainfall. It should be noted that chlorophyll concentrations in Nottely 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 Nottely than in other Tennessee Valley reservoirs located outside the Blue Ridge Ecoregion.
The fish community rated “poor” at the forebay and “fair” at the mid-reservoir location. Historically, the fish communities at both locations have been assessed ratings ranging from the low end of the “fair” range to “good”. In 2017, a total of nineteen species was observed reservoir-wide. The tolerant species, gizzard shad, bluegill, and redbreast sunfish, accounted for a significant portion of the fish assemblage at the forebay. Bluegill, green sunfish, and flathead catfish were the dominant fish species at the mid-reservoir station. Largemouth bass and spotted bass abundance at both locations were similar to long-term averages. Fish health was assessed a “poor” rating with higher than normal incidences of disease and parasites (fungus).
Bottom life rated “poor” at the forebay and “fair” at the mid-reservoir location. Slightly higher density and diversity of bottom-dwelling organisms were found at the mid-reservoir, but those collected at both locations consisted mostly of midges and worms, which are more tolerant of the low dissolved oxygen conditions that develop in the lower water column during summer and autumn. Bottom life typically rates “poor” or “fair” at the forebay and “fair” or “good” at the mid-reservoir.
Sediment quality rated “good” at both monitoring locations because no PCBs or pesticides were detected, and concentrations of metals were within suggested background levels. A “good” rating is typical for sediment quality at both locations, although naturally occurring metals such as arsenic and copper are generally near – slightly above or below – suggested background concentrations. In addition, sediment quality rated “fair” at the mid-reservoir in 1995 because low levels of DDE were detected. DDE is a breakdown product of DDT. DDT entered the environment when it was used as a pesticide.
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 Nottely Reservoir, visit the Georgia Department of Natural Resources.