Watts Bar Reservoir

Ecological health rating

TVA monitored Watts Bar Reservoir annually from 1991 through 1994 to establish baseline data on the reservoir’s ecological health under a range of weather and flow conditions. Watts Bar is now evaluated every other year.

The overall ecological health condition for Watts Bar Reservoir rated a “low fair” in 2006, comparable to results from previous dry years (2000 and 2002). The reservoir ratings for Watts Bar have fluctuated between “high fair” and poor and have generally followed reservoir flow conditions. The indicator most responsive to flow is dissolved oxygen.

Watts Bar Reservoir Ecological Health Ratings, 1994-2006

Click chart for raw data.

The table below shows the ratings for individual ecological health indicators at Watts Bar in 2006. These ratings are briefly explained in the paragraphs that follow.

Monitoring locations	Dissolved oxygen	Chlorophyll	Fish	Bottom life	Sediment
Ecological Health Indicators for Watts Bar Reservoir, 2006
Forebay	Poor	Poor	Fair	Poor	Fair
Mid-reservoir	Good	Poor	Fair	Fair	Good
Tennessee River inflow			Good	Poor
Clinch River inflow			Fair	Fair
Dissolved oxygen Dissolved oxygen rated poor at the forebay and good at the mid-reservoir monitoring location. Low dissolved oxygen (<2 mg/L) in the lower water column at the forebay, primarily during June and July, resulted in a poor rating. The worst dissolved oxygen conditions occurred in 2000, 2002, and 2006 as a result of the reduced flows through the reservoir during dry conditions. TVA has installed aeration equipment to add oxygen to the deep water above Watts Bar Dam and to improve conditions immediately downstream Learn more about these improvements here. Chlorophyll Chlorophyll rated poor at the forebay and mid-reservoir in 2006 because average chlorophyll concentrations were high at both monitoring locations. Annual average chlorophyll concentrations have fluctuated through time at the forebay, with no specific trend through time. Chlorophyll has shown an overall trend of increasing concentrations at the mid-reservoir site since monitoring began in 1991. Fish The fish assemblage rated good or "high fair" at all locations except the Clinch inflow which rated fair. The fish community rated fair at the Clinch inflow location because of the fair diversity of fish and a high composition of tolerant individuals. Better fish diversity at the other locations resulted in higher ratings. Bottom life Similar to most previous years, bottom life rated poor at the forebay and Tennessee inflow locations and fair at the mid-reservoir location. Historically, bottom life rated poor at the Clinch inflow location. However, in 2004 and again in 2006, bottom life at the Clinch inflow rated fair due to an increase in the density and diversity of organisms in the samples collected from the reservoir bottom. Sediment In 2006, lindane was detected for the first time in sediments collected from the forebay and resulted in a fair rating. Sediment quality rated good at the mid-reservoir location because no PCBs or pesticides were detected, and no metals had elevated concentrations. Low levels of PCBs and chlordane, a pesticide previously used to control termites and crop pests, were detected in some previous years at both locations. See definitions of ecological health indicators and monitoring locations.

Fish consumption advisories

The state of Tennessee has issued several fish consumption advisories for Watts Bar Reservoir because of PCB contamination. Striped bass, catfish, and striped bass-white bass hybrids caught in the Tennessee River portion of the reservoir should not be eaten. Additionally, no fish caught in the Poplar Creek Embayment should be eaten due to PCB and mercury contamination.

There is a precautionary advisory for largemouth bass, white bass, sauger, carp, and smallmouth buffalo caught in the Tennessee River portion of the reservoir and catfish and sauger caught in the Clinch River arm. A precautionary advisory means pregnant women, nursing mothers, and children should not consume the fish species named, and all other individuals should limit their consumption to no more than one meal per month.

TVA collected channel catfish and largemouth bass from the reservoir for tissue analysis in the autumn of 2006. The results, which were similar to those of previous years, will be provided to state agencies in Tennessee. TVA plans to collect and analyze channel catfish from the forebay in autumn 2007 for selected pesticides and PCBs.