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Douglas Reservoir

The ecological health of Douglas Reservoir received a “fair” rating in 2022, consistent with previous ratings of low “fair” or “poor”. The ratings are primarily driven by the low dissolved oxygen concentrations that develop in the lower water column during summer and reduced ratings for bottom life.

The ecological health of Douglas 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 Douglas Reservoir—the deep, still water near the dam, called the forebay (French Broad River Mile (FBRM) 34.5); and the middle part of the reservoir (FBRM 51.0).

Douglas Reservoir Ecological Health Ratings, 1994-2022

 

To view or export the data, click on the menu in the top-right corner of the chart.

Ecological Health Score Ranges:
 

 >72 = Good

 

 59-72 = Fair

 

 <59 = Poor

Ecological Health Indicators for Douglas Reservoir ‒ 2022

Monitoring locationDissolved
oxygen
ChlorophyllFishBottom
life

Sediment
ForebayPoorGoodGoodPoorGood
Mid-reservoirPoorFairGoodPoorGood

Dissolved oxygen

Dissolved oxygen rated “poor” at both monitoring locations in 2022, consistent with findings from previous years. Dissolved oxygen concentrations at the forebay and mid-reservoir were low (<2 mg/L) in the bottom half of the water column during summer, resulting in “poor” ratings for this indicator. The deep water and long residence times (time that water spends in the reservoir) of Douglas Reservoir allow oxygen in the lower water column to be depleted as it is used in the natural process of decomposition.  

As part of TVA’s Reservoir Release Improvement Program, TVA has installed aeration equipment at Douglas Dam to improve the quality of water downstream from the dam in the French Broad River. Learn more about these improvements.

Chlorophyll

Chlorophyll in 2022 rated “good” at the forebay and “fair” at the mid-reservoir monitoring location. Summer chlorophyll averages are generally higher at the mid-reservoir location, rating “poor” in most years. Chlorophyll has rated “good” or “fair” at the forebay. Weather conditions, particularly the timing and amount of rainfall, and the related changes in runoff have proven to be major factors in the year-to-year variation.

Fish

Consistent with most previous years, the fish assemblage rated “good” at both monitoring locations in 2022. A total of thirty-three species of fish were observed, including a “good” variety of top carnivores (e.g., largemouth bass), sunfish (e.g., bluegill) and benthic invertivores (e.g., black redhorse). Forage fish such as gizzard shad and spotfin shiners were also abundant. Fish health was assessed a “good” rating with low incidences of disease and parasites.

Bottom life

Bottom life in 2022 rated “poor” at both monitoring locations. As in previous years, TVA found a limited variety of organisms in samples collected from the reservoir bottom, and these were primarily species, such as midges and worms, capable of tolerating low dissolved oxygen conditions.

Sediment

Sediment quality in 2022 rated “good” at both monitoring locations. No PCBs or pesticides were detected in the sediment samples, and concentrations of metals were within suggested background levels. Low levels of PCBs and the pesticide chlordane have been detected in sediment samples from both monitoring locations in some previous years, causing sediment quality to rate “fair”.

Fish consumption advisories

TVA maintains a program to examine contaminants in fish fillets 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 Douglas Reservoir, visit the Tennessee Department of Environment and Conservation web page.