Tims Ford Reservoir

Ecological health rating

Tims Ford Reservoir rated poor in 2008, similar to previous years. Consistent issues are low dissolved oxygen levels in the lower water column and poor ratings for bottom life. Lower ratings for chlorophyll at the mid-reservoir location have been an issue in some years; however, chlorophyll rated good at this location in 2008.

TVA monitors two locations on Tims Ford Reservoir — the deep, still water near the dam, called the forebay, and the middle part of the reservoir. Monitoring is usually done on a two-year cycle.

Tims Ford Reservoir Ecological Health Ratings, 1994-2008

Click chart for raw data.

The table below shows the ratings for individual ecological health indicators at Tims Ford in 2008. These ratings are briefly explained in the paragraphs that follow.

Monitoring locations	Dissolved oxygen	Chlorophyll	Fish	Bottom life	Sediment
Ecological Health Indicators for Tims Ford Reservoir, 2008
Forebay	Poor	Good	Good	Poor	Fair
Mid-reservoir	Poor	Good	Fair	Poor	Fair
Dissolved oxygen As in previous years, dissolved oxygen rated poor at both monitoring locations. Oxygen levels were below two milligrams per liter throughout much of the lower water column during the summer and at or near zero on the bottom from July through October. Chlorophyll Chlorophyll concentrations were within the expected range at both the forebay and mid-reservoir locations, resulting in good ratings. Chlorophyll has rated good at the forebay most years, but ratings at the mid-reservoir have varied between good, fair, and poor. Chlorophyll concentrations have varied in response to the timing and amount of rainfall. However, average chlorophyll concentrations have shown a general trend of increasing at the mid-reservoir location since TVA began monitoring Tims Ford in the early 1990s. Fish The fish assemblages rated at the low end of the good range at the forebay and fair at the mid-reservoir location. The fish assemblage has scored fair or a “low good” at both locations all years monitored. Typically, a good variety of fish are collected, but a large number of them are species such as bluegill and spotfin shiner that are more tolerant of degraded water quality. Bottom life As in previous years, bottom life rated poor at both monitoring locations because few animals were found and most were species able to tolerate poor conditions. Low dissolved oxygen levels near the reservoir bottom are a likely contributing factor. Sediment Sediment quality rated fair at both locations. The forebay received a fair rating due to elevated levels of nickel. Nickel has exceeded the expected background levels at the forebay location in all previous years of monitoring, while arsenic exceeded those levels in 2002. This is the first year that arsenic exceeded expected background levels at the mid-reservoir location, resulting in a fair rating. Low levels of chlordane have been detected at the mid-reservoir location in the past (1996, 1998, and 2002). See definitions of ecological health indicators and monitoring locations.

Fish consumption advisories

There are no fish consumption advisories on Tims Ford Reservoir. TVA collected channel catfish and largemouth bass from the reservoir for tissue analysis in the autumn of 2006. All contaminant levels were either below detectable levels or below the levels used by the state of Tennessee to issue fish consumption advisories. TVA will collect fish from Tims Ford again in the autumn of 2010.