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Kentucky Reservoir

Kentucky Reservoir received a “good” ecological health rating in 2017. Ecological health scores for Kentucky Reservoir have fluctuated between “good” and the upper end of the “fair” range and have generally followed reservoir flow conditions. The indicators most responsive to flow are dissolved oxygen and chlorophyll, which typically receive lower ratings during dry, low flow years. 

The ecological health of Kentucky 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 Kentucky Reservoir—the deep, still water near the dam, called the forebay (Tennessee River Mile 23.0); the middle part of the reservoir (Tennessee River Mile 85.0); the river-like area at the extreme upper end of the reservoir in the Tennessee River (miles 200 to 206), called the inflow; and the Big Sandy embayment (Big Sandy River Mile 7.4)—usually on a two-year cycle. Only bottom life and the fish assemblage are assessed at the inflow monitoring location.

Ecological Health Ratings for Kentucky Reservoir, 1994-2017


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 Kentucky Reservoir, 2017

Monitoring locationDissolved

Big Sandy embaymentPoorPoorGoodPoorGood

Dissolved oxygen

Dissolved oxygen in 2017 rated “fair” at the forebay, “good” at the mid-reservoir, and “poor” at the Big Sandy embayment monitoring location. This indicator has rated “good” at the mid-reservoir all years monitored except 2011, when it rated “fair”. Dissolved oxygen ratings have varied between “good” and “fair” at the forebay and “good”, “fair”, and “poor” at the embayment location.

Prevailing weather patterns and the related changes in reservoir flows are major factors in differing dissolved oxygen conditions from year-to-year. Poorer dissolved oxygen conditions typically occur as a result of reduced flows through the reservoir during dry conditions. Low dissolved oxygen concentrations often develop in a portion of the lower water column during summer at the forebay and embayment locations. However, the low dissolved oxygen exists only for a short time at the forebay, while the more quiescent flows in the embayment reduce water exchange and mixing within the water column, resulting in extended periods with low dissolved oxygen.  


Consistent with dissolved oxygen, chlorophyll rated “fair” at the forebay, “good” at the mid-reservoir, and “poor” at the Big Sandy embayment monitoring location.  Elevated chlorophyll concentrations are common on Kentucky Reservoir, typically rating “poor” or at the low end of the “fair” range at the forebay and embayment locations. By contrast, chlorophyll typically rates “good” at the mid-reservoir because the reservoir is narrower in this reach and flows (i.e. velocities) generally are sufficient to produce mixing within the water column which tends to limit light exposure for phytoplankton/algae. 


The fish assemblage rated “good” at the four locations monitored. Historically, the fish assemblage has rated “good” at the transition and in the “good” to high “fair” range at the other monitoring locations. 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 sixty different species was observed reservoir-wide. Some of the more interesting species observed included American eel, rainbow darter, river darter and silver chub. Additionally, the invasive species silver carp was observed at the forebay, mid-reservoir and embayment locations.

Bottom life

Monitoring results for bottom life in 2017 were generally similar to previous years. Bottom life rated “good” at the forebay, mid-reservoir, and inflow locations and “poor” at the Big Sandy embayment location. Samples from the embayment contained fewer individuals and a lesser variety of organisms than those from the other monitoring locations; the organisms consisted mostly of midges, worms, and small mollusks known as fingernail clams Low “fair” to “poor” ratings are common for Big Sandy and are likely reflective of the low dissolved oxygen conditions that develop in the lower water column each year.


Sediment quality rated “good” at the three locations at which this indicator is monitored: the forebay, mid-reservoir, and Big Sandy embayment. No PCBs or pesticides were detected and concentrations of metals were within expected background levels. Sediment quality commonly rates “good” at the forebay and mid-reservoir locations and “good” or “fair” at the Big Sandy embayment location dependent on arsenic concentrations. Arsenic occurs naturally in soils and the concentrations in sediments deposited in the embayment are generally near — slightly above or below — suggested background concentrations.

Fish consumption advisories

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 Kentucky Reservoir, visit the  Tennessee Wildlife Resource Agency and the  Kentucky Department of Fish and Wildlife Resources.