Watts Bar Reservoir
The overall ecological health condition for Watts Bar Reservoir rated fair in 2012. Ecological health scores for Watts Bar have fluctuated between a “high fair” and poor and have generally followed reservoir flow conditions. Flow conditions in 2012 were low during most of the summer months in response to the generally dry weather pattern. The indicator most responsive to flow is dissolved oxygen, which rated poor at the forebay in 2012. In addition, common problems are elevated chlorophyll concentrations, poor bottom life and the presence of metals and/or organic contaminants in the sediments.
TVA monitors four locations on Watts Bar Reservoir—the deep, still water near the dam called the forebay; the middle part of the reservoir; and the riverlike areas at the extreme upper end of the reservoir in the Tennessee and Clinch rivers, called inflows—usually on a two-year cycle.
Ecological Health Indicators for Watts Bar Reservoir, 2012
|Tennessee River inflow||–||–||Good||Poor||–|
|Clinch River inflow||–||–||Fair||Fair||–|
Dissolved oxygen (DO) rated poor at the forebay and good at the mid-reservoir location. Dissolved oxygen has rated good at the mid-reservoir location all years monitored except 2008 and 2010, when it rated fair and poor, respectively. Low dissolved oxygen levels (<2 mg/l) have occurred in the lower water column at the mid-reservoir in several years, including 2012. However, the area affected was larger in 2010 than in other years, resulting in the only poor rating for this indicator at this location. Ratings have varied between good, fair and poor at the forebay, primarily due to differences in reservoir flows. Poorer DO conditions typically occur as a result of 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 rated poor at both locations monitored because of elevated concentrations. Annual average chlorophyll concentrations have fluctuated through time at the forebay, with no specific trend of increasing or decreasing. Chlorophyll concentrations have shown an overall trend of increasing at the mid-reservoir location since monitoring began in 1990.
The fish assemblage rated good at the Tennessee inflow location and at the upper end of the fair range at other monitoring locations. At all locations, the percent composition of tolerant individuals was higher than expected and catch rates were lower than expected. Better fish diversity at the Tennessee inflow location contributed to the higher (good) rating.
Bottom life rated good at the mid-reservoir, fair at the forebay and Clinch inflow locations and poor at the Tennessee inflow. Scores for bottom life in 2012 were similar to those of previous years at each monitoring location except the Clinch inflow. Bottom life rated poor at the Clinch inflow until 2004 when it received its first fair rating. Since 2004, bottom life at this location has scored within the fair to low-good range. Improvements in ratings at the Clinch inflow are attributable to increases in the density and diversity of organisms in the samples collected from the reservoir bottom.
Sediment quality rated fair at the forebay and mid-reservoir locations because concentrations of arsenic exceeded suggested background levels. Sediment quality commonly rates fair at both locations due to one or more contaminants: PCBs, chlordane and/or arsenic. Additionally, the concentration of copper was elevated in the sample collected at the mid-reservoir location in 2009, and lindane was detected in the sample collected at the forebay in 2006.
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 Watts Bar Reservoir, visit the Tennessee Wildlife Resource Agency.