The Annual Drawdown Is upon Us

As opposed to last year’s drought, the Valley has had an abundance of rain this year. Nevertheless, TVA is drawing down water levels in the tributary reservoirs. Here’s why.

AUGUST 28, 2017—Mother Nature can be mercurial in her temperament. Last year, she afflicted the Tennessee Valley with a severe drought that saw TVA fighting to hold on to every last drop of water in its tributary reservoirs. This year, she graced us in spring and early summer with an abundance of rain—so much that many dams were spilling water, including Norris…a rare occasion indeed.

Throughout the summer this year, most reservoirs in the system have enjoyed full-pool fun, to the delight of recreational users throughout the Valley.

Now, however, comes the inevitable heartbreak of the late-summer drawdown, which is necessary this year—as it is every year—despite the high water levels perceived by many Valley residents.

A Balancing Act

TVA strives to keep as much water in the reservoirs as possible for recreation from June 1 to Labor Day each year. But other responsibilities are also pressing. The River Forecast Center must maintain minimum flows across the entire system—which begins in Knoxville, Tenn., and ends in Kentucky Reservoir in Paducah, Ky.—to preserve water quality; maintain aquatic life; support navigability; preserve flood storage capability; ensure there is enough water to meet industrial, municipal, and agricultural needs; and, yes, cool TVA’s power plants, especially nuclear reactors. (Click here to read more about how TVA manages the river.)

To meet objectives, water is slowly being released from the ten major tributary reservoirs above Chickamauga Dam—Blue Ridge, Chatuge, Cherokee, Douglas, Fontana, Hiwassee, Norris, Nottely, South Holston and Watauga—which is resulting in a decline in lake levels. The tributary reservoirs are all currently in balance, with each providing an equitable share of the water needed downstream.

“Although we were fortunate to receive more than adequate rainfall back in late spring and early summer, conditions have returned a bit more to normal,” says James Everett, River Forecasting Center Operations support manager. “We have gradually, all summer long, been releasing water from our tributary system of dams to balance the various objectives and constraints across the system—in the early part of the summer we were actually releasing more than the minimum necessary to regain and recover flood storage.”

Going with the Flow

Some tributaries may feel the fall more precipitously than others. “Douglas is a huge, deep lake with a 4,000 square mile drainage area. Blue Ridge is a tiny lake with only a 200 square mile drainage area. We’re pulling 20 times more water out of Douglas than at Blue Ridge, but the impact at each lake will be similar. We’re taking 2.6 feet out of Douglas this week, and only 1 foot out of Blue Ridge, but that’s equitable given the size of reservoirs.”

TVA is careful to ensure that one lake never has to bear the burden alone, according to David Bowling, vice president of Land and River Management. Instead there is an emphasis on balancing water releases across the entire system. “But most people don’t realize each reservoir’s individual importance to the health of the entire Tennessee River,” Bowling acknowledges. “What they’d really like is for us to keep their reservoir level high by not releasing any water. What they don’t realize is that their reservoir would stagnate quickly.”

In such a scenario, “we’d have problems on both sides of the dam,” says Bowling, pointing especially to water-quality issues, which are always a particular challenge in the heat of late summer.

Recreation Dog Days

At any rate, Labor Day traditionally marks a turning point where boating season on the lakes is winding down and flood control becomes the focus heading into the autumn, per TVA’s system operating guide. TVA’s strategy to keep water levels as high as possible is replaced by the need to move water out of the system and bring lakes down to winter pool levels.

Until then, there is plenty of fun to be had on TVA lakes and lands, though Everett notes that as Labor Day approaches, shallow areas will grow yet shallower, and caution is needed.

He understands that lakeside homeowners and weekend recreation users alike can feel frustrated as the lake levels go down, particularly when it’s been raining this year. But there’s a catch. “We’ve had plenty of rain, but we’re still behind in run-off,” Everett explains. “That’s a lingering effect of last year’s dry conditions. When you have a severe drought—and we were looking at rainfall deficits in the double digits last year—it takes time for the soil itself to recover. Like a sponge, it has to rewet itself.”

Today, conditions are optimal for water quality and flood storage, and levels are right where they should be to accommodate the possibility precipitation associated with fall’s tropical storms. Hurricane Harvey should remind us all of what havoc such a storm can wreak.

It should never be forgotten that—though recreation is a nice side benefit—one of TVA’s main purposes from the beginning was to prevent flooding. “We’re confident that we can do that,” Everett says.