Ecological health of Chickamauga Reservoir received a “good” rating in 2017, consistent with all years except 2007 and 2011, when Chickamauga rated “fair”. The lower ratings were due to the fact that several indicators concurrently rated at the low end of their historic range.
The ecological health of Chickamauga 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 four locations on Chickamauga Reservoir—the deep, still water near the dam, called the forebay (Tennessee River Mile (TRM) 472.3); the middle part of the reservoir (TRM 490.5); the Hiwassee River embayment (Hiwassee River Mile 8.5); and the river-like area at the extreme upper end of a reservoir, called the inflow (TRM 529.0)—usually on a two-year cycle. Only bottom life and the fish assemblage are assessed at the inflow monitoring location.
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>72 = Good
59-72 = Fair
<59 = Poor
|Hiwassee River embayment||Good||Good||Good||Fair||Good|
Dissolved oxygen in 2017 rated “good” at all locations monitored. Dissolved oxygen has typically rated “good”, except during extremely dry, low flow years such as 2001 and 2007, when this indicator rated “fair” at the forebay. Low flow conditions reduce mixing in the water column and can allow water to sit long enough that oxygen in the lower water column becomes depleted as it is used in the natural process of decomposition.
Chlorophyll in 2017 rated “good” at all locations monitored. Ratings have fluctuated between “good”, “fair, and “poor” at each location, generally in response to reservoir flow conditions.
The fish community in 2017 rated “good” at the inflow and Hiwassee River embayment locations and “fair” at the forebay and mid-reservoir locations. The fish community typically rates “good” or at the upper end of the “fair” range at each location. 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 forty-nine species was observed reservoir-wide. The Hiwassee embayment sample exhibited the highest number of species (38) collected to date for this location.
Bottom life rated “fair” at the forebay and Hiwassee embayment locations and “good” at the mid-reservoir and inflow locations. Ratings typically vary between “good” and “fair” at each location. However, bottom life received a “poor” rating at the Hiwassee location in 2007 because samples contained fewer long-lived and sensitive organisms — such as snails and mayflies — than in other years. The lower rating was likely due in part to the low dissolved oxygen concentrations that developed along the reservoir bottom that year, which was one of the driest years on record.
Sediment quality rated “good” at the mid-reservoir and Hiwassee embayment locations and “fair” at the forebay because low levels of PCBs were detected in one of the two samples collected at this location. Low levels of PCBs are sometimes detected in the sediment samples from each monitoring location. The pesticide chlordane was detected sporadically during the 1990’s. Elevated concentrations of zinc and copper also were commonly found in the sediments during the 1990’s, but their concentrations have exhibited a decreasing trend over the Ecological Health monitoring period (1990 – present). Arsenic also was slightly above suggested background concentrations in some samples in 2001 and 2011. These metals (arsenic, copper, and zinc) occur naturally in soils but can also originate from many sources. One probable source for copper and zinc is the past mining activities in the Copper Basin, while arsenic concentrations in the sediments of many Valley reservoirs are generally near — slightly above or below — the suggested background concentration.
TVA maintains a program to examine contaminants in fillets of fish collected from TVA reservoirs and their major tributary streams on a rotational basis. The data collected from this program are 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 Chickamauga Reservoir, visit the Tennessee Wildlife Resource Agency.