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

Chlorophyll rated fair at the forebay and poor at the mid-reservoir monitoring location.  A poor rating is typical at the mid-reservoir location, but ratings at the forebay have varied between good, fair and 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 the forebay monitoring location, because the number and variety of fish sampled were slightly less than expected.  The mid-reservoir location received its first good rating.  In all other years monitored, the fish community at this location has rated fair, although ratings often were at the upper end of the fair range.  The improved rating at the mid-reservoir was because more species were collected including intolerant species (those most sensitive to degraded water quality or habitat conditions).

Bottom life

Bottom life rated fair at both locations.  Slightly higher density and diversity of animals were found at the mid-reservoir, but the animals collected at both locations were predominantly those tolerant of poor conditions. Bottom life typically rates poor or fair at the forebay and fair or good at the mid-reservoir location. 

Sediment

Sediment quality rated good at the forebay and fair at the mid-reservoir  location. At the forebay, no pesticides or PCBs were detected, and concentrations of metals were within expected background levels.  Copper was slightly above expected background levels at the mid-reservoir. A good rating is typical, although sediment quality also rated fair at the mid-reservoir 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.