River Running from a Desk
TVA’s river management balances hydropower, flood control and recreation and more
Sitting inside a 1,200 square foot room in Knoxville, Tennessee, with hundreds of blinking computer screens and electronic maps that occupy the entire wall, Tennessee Valley Authority engineers work around the clock.
From the windowless room in the TVA’s River Forecasting Center they control the flow of water in a 41,000 square mile drainage area that includes the Tennessee River System and its 10 large eastern tributaries, and 49 dams.
With the click of a mouse or the flip of a switch they can determine whether a group of white water paddlers on the Ocoee River will have a good day, if a barge will have enough water to get its goods to market, or a nuclear plant will have enough water to meet thermal compliance standards.
Most people look at dams as structures to hold back water or as a means of making electricity. They do both, of course, but just as important is their role in managing water levels. For TVA, spilling water is just as critical a function as preventing flooding. One can’t be done without the other, in fact.
Every year between Labor Day and Jan. 1, TVA draws down its reservoir levels to make room for heavy rains of the winter season. In December 2015, 8.6 inches of rain fell in the Tennessee Valley. It was the region’s wettest December in nearly a quarter century with rainfall 185% of normal. The agency estimates that during Christmas 2015, its flood control efforts averted about $136.6 million of flood damage.
On average, TVA reduces flood damage by $250 million every year.
In the summer, the process is reversed. TVA limits releases to a minimum to let lake levels rise as high as possible for summer recreation. TVA reservoirs are home to 230 commercial marinas. “Recreational boaters are among our most avid users and most passionate stakeholders,” David Bowling, general manager of River Management at TVA, says.
In addition to weekend boaters, the TVA system has also hosted Olympic kayaking, on the Ocoee River, which is also home to 24 commercial rafting companies. In Alabama, TVA controls water flows into Guntersville Lake, which is ranked among the top bass fishing destinations in the country and is one of the economic mainstays of Jackson and Marshall counties.
The TVA region also includes 800 miles of commercially navigable rivers, supporting $8 billion in annual economic output to the area by providing passage for barges laden with fertilizer, asphalt, salt, or even rocket engines from the Marshall Space Flight Center in Huntsville, Ala., that are too large to ship any other way.
Navigation, flood control and power generation were set out as the main objectives of TVA when it was established in 1933. Later, in the early 1990s, water quality, water supply, and recreation were added to the mix. When TVA’s larger generation fleet is added to the equation, which includes coal, nuclear, and gas-fired power plants, TVA’s becomes even more complicated.
At some dams, water flows cannot be turned down to zero, but must be maintained to support navigation or downstream aquatic life. At some dams in isolated areas, power generation is used for voltage support. Some hydropower plants are must-run facilities because of limited storage capability or water quality issues. In other cases, economics dictate that a hydropower plant be turned off in order to avoid the steep cost of stopping and starting a coal or nuclear plant.
“Hydro generation is very important to us,” says Bowling. Water flows from TVA’s system keep lights shining, appliances humming and motors running for 9 million people in a territory that touches seven states.
Hydroelectric power is at the heart of those operations, providing electric power that is always available, clean and can respond quickly to changes in demand.
“Every drop of water is important. We want to offset the most expensive power we can.” But he also notes that “every dam has its own set of constraints and operating objectives.” And all contribute to overall system operations.
“It’s a balancing act,” says Bowling, and it is orchestrated from a high tech office in Knoxville.
This article was written by LeRoy Coleman, NHA’s communications manager. For more information on TVA’s hydropower, please visit: www.tva.com/Energy/Our-Power-System/Hydroelectric