Guntersville Reservoir

Ecological health rating

The ecological health condition of Guntersville Reservoir rated fair in 2010. Guntersville’s ecological health scores have fluctuated within the good range all other years except 2008, when Guntersville also rated fair. Similar to 2008, the lower reservoir rating in 2010 was largely because several ecological indicators at the forebay (dissolved oxygen, chlorophyll, and bottom life) received their lowest scores to date, which likely resulted from the generally dry weather pattern and low flow conditions during most of the summer months.

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. In turn, the low dissolved oxygen can negatively affect bottom life.

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

Guntersville Reservoir Ecological Health Ratings, 1994-2010

Click chart for raw data.

The table below shows the ratings for individual ecological health indicators at Guntersville in 2010. 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, 2010
Forebay	Poor	Poor	Fair	Poor	Good
Mid-reservoir	Good	Good	Fair	Good	Good
Inflow			Fair	Good
Dissolved oxygen Dissolved oxygen conditions typically rate good at both monitoring locations, and the mid-reservoir continued to do so in 2010. However, the forebay received its first poor rating. This was because concentrations were low (< 2 mg/l) along the reservoir bottom during June through August. The forebay received its first fair rating in 2008 because dissolved oxygen concentrations were low in a small area along the bottom during June and July of that year. 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. 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 The fish communities rated fair at all locations because the numbers of individuals and variety of species collected were slightly fewer than expected. The fish assemblage generally fluctuates within the fair range 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. The inflow’s rating rebounded in subsequent years, possibly indicating that the poor rating was an anomaly. Bottom life Bottom life rated poor at the forebay and good at the mid-reservoir and inflow locations. The forebay received its first poor rating because of reduced diversity and most of the organisms in samples collected from the reservoir bottom are capable of tolerating poor water quality conditions. Bottom life typically rates fair or good at all monitoring locations. Sediment Sediment quality rated good at both the forebay and mid-reservoir monitoring locations because no PCBs or pesticides were detected, and no metals had elevated concentrations. 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

Guntersville 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 Guntersville Reservoir, visit the Epidemiology Division of Alabama Department of Public Health’s web page. http://www.adph.org/tox/index.asp?ID=1360