The overall ecological health for Tellico Reservoir rated “poor” in 2017. Tellico has rated either “poor” or at the low end of the “fair” range all years except 1994, when it scored slightly higher due primarily to improved chlorophyll concentrations.
The ecological health of Tellico 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 Tellico Reservoir—the deep, still water near the dam, called the forebay (Little Tennessee River Mile (LTRM) 1.0); and the middle part of the reservoir (LTRM 15.0) — usually on a two-year cycle).
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>72 = Good
59-72 = Fair
<59 = Poor
Dissolved oxygen rated “poor” at the forebay and “fair” at the mid-reservoir. Historically, dissolved oxygen ratings at the forebay have fluctuated between “good”, “fair”, and “poor”. This indicator has rated “good” at the mid-reservoir all other years monitored except 2006, when it also rated “fair”. Low dissolved oxygen concentrations have occurred at the mid-reservoir location in several other years, but only for short durations, and the total area of the water column affected remained small enough that conditions rated “good”. Prevailing weather patterns and the related changes in reservoir flows are major factors in differing dissolved oxygen conditions from year-to-year. Poorer dissolved oxygen conditions typically occur as a result of reduced flows through the reservoir during periods of low rainfall and runoff.
Chlorophyll in 2017 rated “poor” at the forebay and “fair” at the mid-reservoir. Higher chlorophyll concentrations can be expected at the forebay because of the exchange of water from the nutrient-rich forebay of Fort Loudoun Reservoir via the canal connecting the two reservoirs. However, concentrations were higher than expected at the mid-reservoir location given the nutrient-poor soils in the upstream watershed. Chlorophyll typically rates “poor” at the forebay and “fair” or “poor” at the mid-reservoir location.
It should be noted that chlorophyll concentrations in Tellico 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 Tellico than in other Tennessee Valley reservoirs located outside the Blue Ridge Ecoregion, such as Fort Loudoun Reservoir.
The fish assemblage in 2017 rated “fair” at the forebay and “good” at the mid-reservoir. Historically, ratings for the fish assemblage have fluctuated between “good’ and “fair” at both locations. In 2017, the number and variety of fish observed at each location were consistent with long-term averages, and fish health was assessed a “good” rating with low incidences of disease and parasites. A total of thirty-eight different species was observed reservoir-wide. Bluegill, spotfin shiners and brook silversides accounted for a significant portion of the fish observed.
As in previous years, bottom life rated “poor” at both monitoring locations because few organisms were collected and most were species capable of tolerating a wide range of environmental conditions. Low dissolved oxygen concentrations and cold temperatures in the lower water column are likely factors contributing to the rating.
Sediment quality rated “good” at both monitoring locations. No PCBs or pesticides were detected and concentrations of metals were within suggested background levels. Sediment quality rated “good” in most years prior to 2017, but the detection of PCBs or pesticides (chlordane and aldrin) and/or elevated levels of arsenic has resulted in some “fair” ratings. Arsenic occurs naturally in the soils and concentrations in sediments deposited in the reservoir are generally near – slightly above or below – suggested background concentrations. The pesticides chlordane and aldrin were detected in sediment samples collected from Tellico Reservoir in the early 1990’s. These pesticides were banned from use in the 1970s and 1980s. However, they continue to be detected sporadically in sediments because of their persistence in the environment. Similarly, PCBs were banned from commercial production in 1979, though they may be present in products and materials produced before the ban. PCB concentrations have, however, declined in fish samples collected from Tellico Reservoir.
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 Tellico Reservoir, visit the Tennessee Wildlife Resource Agency.