Fontana Reservoir rated “fair” in 2016, a similar rating to previous years in which the full complement of indicators was measured.
In 1994, 1995, and 2000 the overall health score was slightly higher. This was partly because bottom life was not sampled at all locations in these years. Bottom life usually rates “poor” on Fontana and probably would have reduced the overall score by several points.
The ecological health of Fontana Reservoir has been monitored using the same methodology since 1994. Ecological health evaluations focus on five indicators: dissolved oxygen, chlorophyll, sediment quality, benthic macroinvertebrate community (bottom life), and the fish assemblage. TVA monitors three locations on Fontana Reservoir—the deep, still water near the dam, called the forebay (Little Tennessee River Mile (LTRM) 62.0); and two mid-reservoir locations (LTRM 81.5 and Tuckasegee River Mile 3.0.
Ecological Health Ratings for Fontana Reservoir, 1994-2016
To view or export the data, click on the menu in the top-right corner of the chart.
>72 = Good
59-72 = Fair
<59 = Poor
Ecological Health Indicators for Fontana Reservoir, 2016
|Mid-reservoir: Little Tennessee River arm||Good||Good||Fair||Good||Good|
|Mid-reservoir: Tuckasegee River arm||Poor||Fair||Good||Poor||Good|
Ratings for dissolved oxygen varied by monitoring location, rating “good” at the Little Tennessee mid-reservoir, “fair” at the forebay, and “poor” at the Tuckasegee mid-reservoir.
In previous years, dissolved oxygen has rated “good” or “fair” at the forebay and Little Tennessee mid-reservoir locations and “fair” or “poor” at the Tuckasegee location, with one exception. The area of the water column with low dissolved oxygen was substantially smaller at the Tuckasegee location in 2004 than in other years, resulting in the only “good” rating for dissolved oxygen at this location.
Areas of low dissolved oxygen are mostly the result of the reservoir’s basic characteristics. Fontana is a very deep tributary storage reservoir with a long summer retention time; it can take more than 150 days for water to move through the reservoir. As the summer sun heats on the surface of the reservoir, a warmer layer of water forms on top of a cooler layer. The layers do not mix, and the bottom layer becomes devoid of oxygen as the oxygen is used up by decaying plants and other materials that settle to the bottom.
Chlorophyll rated “good” at the forebay and Little Tennessee mid-reservoir locations and “fair” at the Tuckasegee mid-reservoir. Chlorophyll has rated “good” at the forebay all years monitored, while ratings have fluctuated between “good”, “fair”, and “poor” at both mid-reservoir locations. Because of their proximity to the two major river inflows (Little Tennessee and Tuckasegee Rivers), chlorophyll concentrations at the mid-reservoir locations are more influenced by the nutrients flowing into the reservoir. Therefore, chlorophyll concentrations at these locations have been more variable in response to the timing and amount of rainfall.
It should be noted that chlorophyll concentrations in Fontana Reservoir are assessed relative to expectations for the Blue Ridge Ecoregion, which has naturally low nutrient concentrations. Therefore, chlorophyll concentrations are expected to be much lower in Fontana than in other Tennessee Valley reservoirs located outside the Blue Ridge Ecoregion.
The fish community rated “good” at the forebay and Tuckasegee mid-reservoir and high “fair” at the Little Tennessee River mid-reservoir. Historically, all three locations have been assessed “good” or high “fair” ratings. In 2016, a total of twenty fish species was observed. Catch rates, overall, were low but the diversity of fish collected was good and fish health was assessed a “good” rating with low incidences of disease and parasites.
Bottom life rated “good” at the Little Tennessee mid-reservoir location and “poor” at both the forebay and Tuckasegee mid-reservoir. “Poor” or low “fair” ratings are common for each monitoring location because relatively few organisms, mainly midges and worms that are capable of tolerating a wide variety of environmental conditions, are typically collected from the reservoir bottom. In 2017, the collection of additional organisms (Asiatic clams, Hexagenia mayflies and alder flies) at the Little Tennessee mid-reservoir location resulted in the only “good” rating for bottom life for Fontana Reservoir.
Sediment quality rated “good” at the three monitoring locations because no PCBs or pesticides were detected and all metal concentrations were within expected ranges. In the 1990s, sediment ratings fluctuated between “good” and “fair” at each location depending on whether the pesticide chlordane was detected in the samples. Chlordane was last detected in the reservoir sediments in 1996, and only at the mid-reservoir monitoring locations. Subsequently, the only “fair” ratings were for the Little Tennessee mid-reservoir location. Chromium exceeded suggested background concentrations at this location in 2008 and copper exceeded those concentrations in 2010. However, neither copper nor chromium has been above suggested background levels in other monitoring years.
Fish consumption advisories
TVA maintains a program to examine contaminants in fillets of fish collected from TVA reservoirs and their major tributary streams on a rotational basis. The data collected from this program are 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 Fontana Reservoir, visit the North Carolina Department of Health and Human Services.