Nottely Reservoir

Dissolved oxygen

Dissolved oxygen rated poor at both the forebay and mid-reservoir monitoring locations. A large proportion of the water column contained low dissolved oxygen concentrations during mid-to- late summer at these locations. This is similar to all previous years, except 2001 when oxygen concentrations were significantly higher at the forebay and rated good, and 2005 when significant rain events in late summer helped replenish oxygen in the upper reaches of the reservoir, resulting in a fair rating at the mid-reservoir location. Although dissolved oxygen typically rates poor at both locations, the extent and duration of low dissolved oxygen has varied in response to the timing and amount of rainfall.

Chlorophyll

Average summer chlorophyll concentrations were elevated at both monitoring locations, rating poor. A poor rating is typical at the mid-reservoir location, but ratings at the forebay have varied from good to fair to poor. As with dissolved oxygen, 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 Nottely in the early 1990s.

Fish

As in previous years, the fish community rated fair at both monitoring locations. The condition of the fish community continues to rate fair, rather than good, because of reduced species diversity and density.

Bottom life

Bottom life rated poor at the forebay because of the low density and diversity of organisms collected. This indicator rated at the low end of the fair range at the mid-reservoir location where higher densities of animals were found. Bottom organisms at both locations were predominantly those tolerant of poor conditions.

Sediment

Sediment quality rated good at both locations. No pesticides or PCBs were detected, and concentrations of metals were within expected background levels. A good rating is typical, although sediment quality rated fair in 1995 because low levels of DDE were detected. DDE is a breakdown product of DDT. DDT entered the environment when it was used as a pesticide.

See definitions of ecological health indicators and monitoring locations.