Ecological Health Rating
The ecological health of Wheeler Reservoir rated “fair” in 2021. Wheeler Reservoir rated either “good” or “fair” in all previous years except 2007 and 2011, when it rated “poor”. Generally, lower ecological health scores occur during years with lower flow. Low flow conditions typically result in higher chlorophyll concentrations and lower dissolved oxygen concentrations.
The ecological health of Wheeler 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 four locations on Wheeler Reservoir—the deep, still water near the dam, called the forebay (Tennessee River Mile (TRM) 277.0); the middle part of the reservoir (TRM 295.9); the Elk River embayment (Elk River Mile 6.0); and the river-like area at the extreme upper end of the reservoir, called the inflow (TRM 348.0)—usually on a two-year cycle. Only bottom life and the fish assemblage are assessed at the inflow monitoring location.
Ecological Health Ratings for Wheeler Reservoir 1994-2021
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
Ecological Health Indicators for Wheeler Reservoir - 2021
|Elk River embayment||Poor||Poor||Good||Poor||Good*|
*Sediment quality was assessed based on monitoring results from 1994 through 2019.
Dissolved oxygen in 2021 rated “good” at the mid-reservoir, “fair” at the forebay, and “poor” at the Elk River embayment location. The lower ratings were due to low dissolved oxygen concentrations (<2 mg/L) in the lower water column during summer. Dissolved oxygen has rated “good” at the mid-reservoir location in all previous years, but ratings have varied between “good”, “fair”, and “poor” at the forebay and embayment locations, primarily in response to reservoir flows.
Chlorophyll rated “good” at the mid-reservoir and “poor” at the forebay and Elk River embayment locations because concentrations were elevated in most of the samples collected. Elevated chlorophyll concentrations are common for Wheeler Reservoir, but dry periods tend to result in even higher chlorophyll concentration by reducing flows through the reservoir and allowing more time for algae to utilize available nutrients. Chlorophyll typically rates “poor” at the forebay and Elk River embayment locations, but ratings have varied between “good”, ”fair”, and “poor” at the mid-reservoir.
The fish assemblage in 2021 rated “good” at the four locations this indicator is monitored. Historically, the fish assemblage has rated “good” at the forebay and in the “good” to “fair” range at the other monitoring locations. In 2021, the number and variety of fish observed at each location were consistent with long-term averages. A total of fifty-one species were observed in 2021. Top carnivores (e.g., largemouth bass), benthic invertivores, and intolerant species (species known to require good water quality conditions) were well represented at each location. Some of the more interesting species included bowfin at the inflow location, and orangespotted sunfish, Tuscumbia darter, and stripetail darter at the mid-reservoir. Fish health was assessed a “good” rating at all locations except the inflow where instances of disease and parasites were slightly higher than desired.
Consistent with most previous years, bottom life in 2021 rated “poor” at the forebay and Elk River embayment monitoring locations and “good” at the mid-reservoir and inflow. The “poor” ratings were due to relatively sparse populations, predominantly composed of animals able to tolerate the low dissolved oxygen concentrations that developed along the reservoir bottom during summer.
Sediment samples were not collected from Wheeler Reservoir in 2021. Sediment quality was assessed for each location based on sampling results from 1994 through 2019. Sediment quality was assigned a “good” rating for the forebay and Elk River embayment locations. Low levels of PCBs were detected in sediment samples from the forebay in 2011 and 2013, and from the Elk River embayment in 2011. No other constituents have had concentrations above background levels at these monitoring locations. Sediment quality was assigned a “fair” rating for the mid-reservoir location. Low levels of the pesticide DDT, or its breakdown products DDE and DDD, were detected in sediments samples from the mid-reservoir location in 1994, 1995, 2015, and 2019. Low levels of Chlordane and PCBs were also detected at the mid-reservoir location in 2003 and 2017, respectively.
Fish consumption advisories
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 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 Wheeler Reservoir, visit the Alabama Department of Public Health (ADPH) web page.