The ecological health of Cherokee Reservoir rated “poor” in 2021 consistent with most previous years. Cherokee rated “fair” in 1995 and 2008. This was because several ecological indicators concurrently rated at the upper end of their historical range. Cherokee is a relatively deep storage impoundment with a long retention time and plenty of nutrients, resulting in low dissolved oxygen concentrations and high chlorophyll levels.
The ecological health of Cherokee 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 fish assemblage. TVA monitors two locations on Cherokee Reservoir — the deep, still, water near the dam, called the forebay (Holston River Mile 55.0), and the middle part of the reservoir (Holston River Mile 76.0).
To view or export the data, click on the menu in the top-right corner of the chart.
>72 = Good
59-72 = Fair
<59 = Poor
*Sediment quality was assessed a “fair” rating based on monitoring results from 1994 through 2018.
As in previous years, dissolved oxygen rated “poor” at both monitoring locations. A large portion of the lower water column had low dissolved oxygen concentrations during the summer months, and there were periods of time when virtually no oxygen was present in the water near the bottom. TVA has installed aeration equipment to add oxygen to the deep water above Cherokee Dam and to improve conditions immediately downstream in the Holston River.
Chlorophyll rated “good” at the forebay but “fair” at the mid-reservoir monitoring location because concentrations were elevated during several sample periods. Chlorophyll typically rates “poor” or at low end of the “fair” range at the mid-reservoir location. Ratings for the forebay have fluctuated between “good” and “fair”; annual variations in the amount of rainfall and runoff have been an important factor.
The fish community rated “good” at both monitoring locations. Historically, ratings for the fish community have fluctuated between “good’ and “fair” at both locations. In 2021, the number and variety of fish observed at both locations were consistent with long-term averages, and fish health was assessed a “good” rating with low incidences of disease and parasites. A total of twenty-eight different species were observed reservoir wide.
Bottom life rated a “low-fair” at the forebay and “poor” at the mid-reservoir. Ratings for bottom life have fluctuated between “fair” and “poor” at both locations. However, most of the animals collected each year are those capable of tolerating poor water quality conditions. “Fair” ratings typically are the result of improvements in the numbers of tolerant organisms collected rather than an improvement in the variety of organisms.
Sediment samples were not collected from Cherokee Reservoir in 2021. Sediment quality was assessed a “fair” rating at both locations based on monitoring results from 1994 through 2018. In 2015 and 2018, sediment quality rated “good” at both locations because no PCBs or pesticides were detected in the sediment samples, and the concentrations of metals were within suggested background levels. In 2012, low levels of PCBs were detected in the sample from the forebay, and the concentration of copper was slightly above the suggested background level in the sample from the mid-reservoir. Copper concentrations have been slightly above suggested background levels most years at the mid-reservoir location. Chlordane, a pesticide previously used to control termites and crop pests, was detected in the sediment sample from the mid-reservoir in 1998 and in the sediment samples from both locations in 1996.
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 Cherokee Reservoir, visit the Tennessee Wildlife Resource Agency.