Chickamauga Reservoir

The ecological health of Chickamauga Reservoir rated fair in 2011. Ecological health scores for Chickamauga have fluctuated within the good range all other years except 2007, when Chickamauga also rated fair. The lower ratings in 2007 and 2011 were due to the fact that several indicators concurrently rated at the low end of their historic range or lower than in other years. In 2007, the combined scores for three indicators—dissolved oxygen, chlorophyll and bottom life—were lower than in other years, but lower ratings for fish and sediment quality in 2011 also contributed to the lower ecological health rating.

TVA monitors four locations on Chickamauga Reservoir—the deep, still water near the dam, called the forebay; the middle part of the reservoir; the Hiwassee River embayment; and the riverlike area at the extreme upper end of a reservoir, called the inflow—usually on a two-year cycle.

Ecological Health Indicators at Chickamauga Reservoir — 2011

Monitoring locationDissolved
oxygen
ChlorophyllFishBottom
life

Sediment
Forebay Good Poor Fair Fair Fair
Mid-reservoir Good Poor Fair Fair Fair
Hiwassee River embayment Good Good Fair Fair Fair
Inflow     Good Good  

Dissolved oxygen

Dissolved oxygen (DO) rated good at all locations monitored. DO typically rates good, except during extremely dry, low-flow years such as 2001 and 2007, which can result in the development of low DO conditions near the bottom and fair ratings. Low DO (<2 mg/L) conditions also developed at the forebay and transition locations in 2011, but only for a short time, and the total area of the water column with low DO remained small enough that conditions rated good.

Chlorophyll

Chlorophyll rated poor at the forebay and mid-reservoir locations because concentrations were elevated in a majority of the samples collected. Chlorophyll rated good at the Hiwassee location. Ratings have fluctuated between good, fair and poor at each location, generally in response to reservoir flow conditions, but annual average concentrations indicate a trend of increasing levels at the forebay and mid-reservoir locations.

Fish

The fish community rated good at the inflow and fair at the three other monitoring locations because the numbers of individuals and variety of species collected was slightly fewer than expected, and a greater proportion of those were tolerant individuals. The fish community typically rates good or at the high end of the fair range. In 2001, the fish community composition was dominated by a few species such as bluegill, gizzard, shad and non-native silversides, which lowered the ratings at these sites.   

Bottom life

Bottom life rated good at the inflow and fair at the three other monitoring locations. Ratings typically vary between good and fair at each location.  However, bottom life scored at the low end of the fair range at the mid-reservoir in 2011—lower than in previous years. Lower scores at the forebay and embayment were second only to those in 2007, which has been the lowest scoring year for these two monitoring locations. The lower scores for bottom life in 2007 and 2011 were likely due in part to the low dissolved oxygen conditions that developed along the reservoir bottom.

Sediment

Sediment quality rated fair at all monitoring locations. PCBs were detected at each location and arsenic concentrations were slightly higher than expected background levels at the forebay and mid-reservoir. Elevated concentrations of PCBs, chlordane and selected metals—generally zinc and copper—have been detected in sediment samples from the forebay and Hiwassee embayment monitoring locations in some previous years. Arsenic also was above background levels in samples collected at the forebay in 2001. These metals (arsenic, copper and zinc) occur naturally in soil, and their concentrations in sediment deposited in the reservoir are generally near—slightly above or below—suggested background concentrations.

Fish consumption advisories

Chickamauga Reservoir—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 Chickamauga Reservoir, visit the Tennessee Wildlife Resource Agency's Web page.