Guntersville Reservoir

Ecological health rating

The ecological health condition of Guntersville Reservoir rated at the upper end of the fair range in 2008. Guntersville’s ecological health scores had fluctuated within the good range in prior years. The lower score in 2008 was largely because several ecological indicators at the forebay (dissolved oxygen, chlorophyll, and bottom life) received their lowest scores to date.

Ecological health scores tend to be lower in most Tennessee River reservoirs during years with lower flows because chlorophyll concentrations are typically higher and dissolved oxygen levels are lower. As in past years, scores for the ecological health indicators at the mid-reservoir and inflow locations were among the highest observed for all TVA reservoirs.

Guntersville Reservoir Ecological Health Ratings, 1994-2008

Click chart for raw data.

The table below shows the ratings for individual ecological health indicators at Guntersville 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 Guntersville Reservoir, 2008
Forebay	Fair	Poor	Fair	Fair	Fair
Mid-reservoir	Good	Good	Fair	Fair	Good
Inflow			Fair	Good
Dissolved oxygen Dissolved oxygen levels typically rate good at both monitoring locations, and the mid-reservoir continued to do so in 2008. However, the forebay received its first fair rating for dissolved oxygen, rating at the upper end of the fair range. This was because concentrations were low in a small area along the bottom of the reservoir in early summer. Chlorophyll Chlorophyll rated poor at the forebay and good at the mid-reservoir monitoring location. Chlorophyll concentrations were elevated at the forebay during several sample periods, likely a result of the low flow conditions in the reservoir. Chlorophyll ratings have fluctuated between good, fair, and poor at the forebay, generally in response to reservoir flows. Chlorophyll concentrations at the mid-reservoir monitoring location have consistently rated good. Fish As in previous years, low catch rates contributed to fair ratings for the fish community at all locations. While the fish assemblage generally rates fair at the forebay and mid-reservoir, ratings at the inflow have fluctuated between good and fair and even poor in 2000 (one point from fair), the lowest score to date for the reservoir. This fish rating rebounded to good in 2002 and to a “high fair” in 2004, possibly indicating that the poor rating was an anomaly. Bottom life Bottom life rated fair at the forebay and mid-reservoir and good at the inflow. Bottom life typically rates fair or good at all monitoring locations. However, bottom life rated at the low end of the fair range at the forebay in 2008 — lower than in previous years. The lower rating was due to the reduced density and diversity of organisms in the samples collected from the reservoir bottom. Sediment Sediment quality rated good at the mid-reservoir monitoring location because no PCBs or pesticides were detected, and no metals had elevated concentrations. The forebay rated fair because PCBs were detected. Sediment quality typically rates fair at the forebay due to the presence of one or more contaminants: PCBs, chlordane, or zinc. The sediment rating at the mid-reservoir has fluctuated between good and fair due primarily to chlordane, which was detected in 1996, 2002, and 2004; PCBs were detected at this location in 2002. See definitions of ecological health indicators and monitoring locations.

Fish consumption advisories

There are no fish consumption advisories on Guntersville Reservoir. TVA collected channel catfish and largemouth bass from the reservoir for tissue analysis in the autumn of 2004. All contaminant levels were either below detectable levels or below the levels used by the state of Alabama to issue fish consumption advisories. TVA will analyze fish from Guntersville again in autumn 2008.