Compared to 2007, Douglas Lake is luxuriously full—just four feet below the ideal summer level established by the Tennessee Valley Authority, not 12 feet down. "No rain destroyed us last year," says Bill Baker, of Swann's Marina on Douglas Lake. "But this year the water is up and we can rent our boats and wave runners. We only lack four feet of water and that has not bothered us."
The still-reduced water levels at Douglas Dam and other TVA-managed Tennessee River reservoirs are bothering the power producer, though. Operating in conservation mode since February 2007, TVA is releasing only enough water to protect downstream water quality and prevent riverbeds below tributary dams from drying out. No additional water is released solely for power production, and producing power only during the multi-purpose water releases has cut hydropower generation to just 56 percent of normal since January 1 and 47 percent of normal for TVA's 2008 fiscal year, which began Oct. 1, 2007.
Water is TVA's lowest-cost generation method, so employing alternatives will likely drive up utility bills, says TVA spokesperson Gil Francis.
"When we don't have the hydropower, we have to burn more coal or use nuclear-generated power, and that's more expensive," he says. "We may also have to buy power from another utility, and that's going to cost more almost every time than power we generate ourselves. The consumer will see an impact on their utility bills, because these increased costs mean we'll have to raise the price to distributors of TVA power, which will raise the consumer's bill."
The water shortfall is the result of last year's drought, the driest year on record in 118 years. This year's improved but still-below-average rainfall cannot overcome the deficit, particularly when overly dry ground is absorbing much of the runoff that would ordinarily reach streams, rivers, and reservoirs. As of May 28, average rainfall in the valley above and east of Chattanooga totaled 17 inches, around 80 percent of normal, but the accompanying runoff is just 54 percent of normal for the year—and that's the water TVA is relying on.
TVA lowers water levels in the reservoirs in the fall and winter so it has the capacity to potentially store storm waters that could cause flooding downstream. In the spring, it holds back reservoir water so lake levels are high enough for summer recreation. As of May 28, TVA reservoirs are an average of six feet below normal. Only Blue Ridge Reservoir in north Georgia is at a normal level. South Holston Reservoir in upper East Tennessee is 10 feet below its normal level for this time of year.
To reach summer levels and be able to resume water releases solely for power production would require a good three to six inches of rain, "right now," says Francis. That's unlikely except in isolated spots; more likely is that TVA will continue its water-release balancing act with the added pressure of summer heat, which evaporates more of the precious rain and requires more cooling water for power plants along the river.