Wilson Reservoir

The overall ecological health of Wilson Reservoir rated “fair” in 2022. Ratings for Wilson Reservoir have fluctuated in a pattern that generally follows reservoir flow conditions, primarily due to the influence of flows on dissolved oxygen in 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. Additional information about each indicator is provided in the paragraphs that follow.

The ecological health of Wilson 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 Wilson Reservoir — the deep, still water near the dam, called the forebay (Tennessee River Mile 260.8), and the river-like area at the extreme upper end of the reservoir, called the inflow (Tennessee River Mile 273 to 274). Only bottom life and the fish assemblage are assessed at the inflow monitoring location.

Wilson Reservoir Ecological Health Ratings, 1994-2022

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 Wilson Reservoir - 2022

Dissolved oxygen

Dissolved oxygen rated “poor” in 2022 due to low concentrations (<2 mg/L) in the lower water column during May through August. Historically, ratings have fluctuated between “fair” and “poor” in response to the timing and amount of rainfall. Low dissolved oxygen concentrations are not uncommon in the lower water column of mainstream Tennessee River reservoirs during low flow years. Although oxygen concentrations in the upper water column remain adequate for aquatic life, the animals that live on or in the sediments can be exposed to low concentrations.

Chlorophyll

Chlorophyll rated “fair” in 2022. Elevated chlorophyll concentrations are common for Wilson 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 ratings have varied between “fair” and “poor”, with the exception 1998, when chlorophyll rated “good”.

Fish

The fish community in 2022 rated “good” at both monitoring locations. The fish community has consistently rated “good” at the forebay, and other than a single “poor” rating in 2000, ratings for the fish community at the inflow have fluctuated between “good” and “fair”.

In 2022, the number and variety of fish observed at both monitoring locations were consistent with long-term averages, and fish health was assessed a “good” rating due to low incidences of disease and parasites. A total of forty-four species were observed in 2022. 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.

Bottom life

Bottom life in 2022 rated “good” at the inflow and “poor” at the forebay location. Bottom life at the forebay has rated “poor” or at the low end of the “fair” range each year. Low oxygen concentrations at the reservoir bottom and the lack of diverse structural habitat are limiting factors to bottom life. At the inflow location, this indicator has received “good” or “high-fair” ratings. A “good” variety of organisms are typically found at the inflow, including long-lived and sensitive organisms which are indicative of good water quality and conditions that allow for long-term survival.

Sediment

Sediment quality rated “good” in 2022. No PCBs or pesticides were detected in the sediment samples, and concentrations of metals were within suggested background levels. Sediment quality usually rates “good” in Wilson Reservoir, but low levels of PCBs and DDE were detected in 2012 and the pesticide chlordane, previously used to control termites and crop pests, was detected in 1998 and 2004, resulting in “fair” ratings.

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 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 Wilson Reservoir, visit the Alabama Department of Public Health (ADPH) web page.