The overall ecological health condition for Hiwassee Reservoir rated fair in 2012, similar to all previous years monitored except 2006, when Hiwassee received a good rating. That was largely because bottom life rated at the upper end of its historic range at both monitoring locations in 2006. Throughout the years, common issues have been elevated chlorophyll concentrations, low dissolved oxygen concentrations in the lower water column, and poor ratings for bottom life.
TVA monitors two locations on Hiwassee Reservoir—the deep, still water near the dam called the forebay, and the middle part of the reservoir—usually on a two-year cycle.
Dissolved oxygen rated poor at both monitoring locations because concentrations were low (<2 mn/L) in a portion of the lower water column during the summer. Dissolved oxygen has rated poor most years at the forebay, but ratings at the mid-reservoir have varied between good, fair and poor.
Chlorophyll rated good at both monitoring locations. Annual average chlorophyll concentrations have fluctuated through time at both locations, resulting in good, fair and poor ratings.
The fish community rated good at both monitoring locations. The fish community rated good all years except 2008, when it rated at the upper end of the fair range at the forebay because species diversity and catch rates were slightly lower than expected.
Bottom life rated poor at the forebay and fair at the mid-reservoir. This is comparable to the poor to “low fair” ratings in most previous years. The benthic communities at both monitoring locations are characterized by low density and diversity of organisms.
Sediment quality rated good at the mid-reservoir and fair at the forebay because low levels of PCBs were detected. Chlordane was detected in samples from both locations in 1993 and 1998; no other contaminants have recorded concentrations above background levels.
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 Hiwassee Reservoir, visit the Epidemiology Division of North Carolina Department of Health and Human Services.