Drought results in very low levels on area reservoirs
Extended drought conditions across the Tennessee Valley have caused the tributary reservoirs on the Tennessee River system to stay well below their targeted levels for this time of year, and some reservoirs have already reached winter levels. Water levels in tributary reservoirs in the eastern part of the Valley are averaging 23 feet below normal.
Water levels in main-river reservoirs are near normal because they have less storage space than tributary reservoirs, and because the main river channel must have deep enough water for commercial barge traffic.
“Any rainfall will help,” said TVA Senior Vice President of River Operations Janet Herrin. “However, at this point, with a 15-inch rainfall deficit in 2007, we would not expect even the remnants of a tropical storm or hurricane to have a significant impact on the tributary reservoirs.”
As part of the Reservoir Operations Study implemented in 2004, TVA restricts how much water it releases from the tributary reservoirs from June 1 through Labor Day, so there’s more water for recreation. Throughout the summer, TVA releases only enough water from upstream reservoirs to protect aquatic species and meet other downstream needs.
On Aug. 1, TVA increased its water releases from the tributary reservoirs to meet minimum flow requirements downstream. Coupled with the lack of rain throughout the year, the releases during August resulted in the current low levels.
After Labor Day weekend, TVA begins an unrestricted drawdown of reservoirs to reach winter levels. This year, however, many reservoirs already are at or near their winter levels, so TVA plans to continue releasing only enough water for minimum flows through the river system. This means tributary reservoir levels will drop at a slower rate than usual this fall.
Herrin said all tributary reservoirs are drawn down proportionately as TVA maintains the minimum flows. “We draw water from the tributary reservoirs as fairly as possible, so everyone sees the same impacts,” she said.
In the eastern part of the Valley, rainfall for the year is 42 percent below normal, and runoff (the amount of water that reaches the reservoirs) is 52 percent below normal. Because of the lack of rain and runoff all year, TVA has moved only enough water through the system for minimum flows since February.
No additional water has been withdrawn for hydro generation. As a result, hydro generation is about 40 percent below normal for the year, and TVA has been forced to buy more power than planned to meet the record power demands that occurred during August.
In addition, with the drought and unusually high August temperatures, TVA has cut back on power production several times during recent weeks at some of its most efficient coal and nuclear plants to keep river temperatures from exceeding state environmental limits.
View information on each reservoir’s daily level.