Providing benefits all along the way
A rain drop’s long journey
Storm clouds gather over the mountains of western North Carolina. Thunder rumbles, lightning flashes, and rain pelts the ground. Soon, rivulets of water are making their way into a nearby creek and, before long, a gully washer is underway.
Follow the journey of just one of those many drops of rain over the next several months, and you start to see the incredible variety of purposes for which the water is used. You also begin to get an idea of the value of an integrated river system, says Chuck Bach, manager of River Scheduling at TVA.
“The Tennessee River system is one of the most intensively used river systems in the country. By managing the dams, reservoirs, and power plants along its length as a unit, TVA is able to get the most value from the available water. Not only can we use every drop over and over; we can schedule dam releases to ensure water is available where and when it is needed.”
Let’s say our rain drop fell near Franklin, North Carolina. There it entered a local creek either as ground water or surface runoff. That creek became a larger stream, which joined the Little Tennessee River and eventually emptied into Fontana Reservoir.
Because the rainfall event that produced our water drop was part of a larger storm system—the kind that covers the entire Tennessee Valley for days at a time in the winter and early spring—it will likely be held in Fontana at least until downstream floodwaters begin to recede.
That’s one of the primary benefits of TVA’s integrated system, says Bach. “The large reservoirs on tributary rivers in the eastern portion of the Tennessee Valley were planned primarily to protect Chattanooga from flooding. Fontana, for example, has 514,000 acre-feet of storage during the winter flood season. That’s a volume equal to one foot of water covering 514,000 acres of land. When there’s a major storm and a risk of flooding, we use this storage space to hold back the rainfall and runoff, which reduces—and often prevents—flooding downriver of the dam.”
What happens to our rain drop next depends on the weather and the time of year. Bach explains: “Beginning in mid-March, we hold as much water in the tributary reservoirs as possible to bring pool elevations up to summer target levels. Then we try to maintain those levels from June 1 through Labor Day. If it’s dry, like it’s been the past two summers, we only release enough water to provide minimum downstream flows. But, if there’s plenty of rain, we’ll use some of the stored water through the summer to produce hydroelectricity and other benefits. The water we release is replaced by the additional rainfall, so recreation use isn’t impacted.”
If, on the other hand, our rain drop fell in late September or October, chances are it will be released through Fontana Dam as soon as it stops raining and the danger of flooding is over. That’s because, after Labor Day, TVA’s operating objective is to lower tributary reservoirs in preparation for the flood season.
Either way—if it was held in Fontana Reservoir to support recreation or released through the turbines at the dam to produce hydropower—we have received more value out of our water drop.
That value multiplies as our rain drop continues its journey, flowing next into Tellico Reservoir where it provides additional recreation benefits before it is diverted through a short canal into Fort Loudoun Reservoir.
When our drop of water enters Fort Loudoun, it becomes part of the main Tennessee River. At that point, its importance to commercial navigation increases, says Bach.
“TVA is responsible for making sure the main-river channel is deep enough for barge traffic. Our integrated system allows us to maintain this depth by releasing water from upstream reservoirs if needed. That means that commercial navigation can continue uninterrupted even during dry periods.”
The availability of the river as a dependable and efficient transportation option benefits us all, according to Bach. “Shipping goods by barge rather than by truck or rail reduces transportation costs by about $500 million each year. Rail and other non-waterway users save another $500 million since railroads need to keep rates low to compete with water transportation. We’d be paying more for all kinds of products if it weren’t for those barges moving up and down the river. Anything made from materials shipped in large quantities—grain, stone and gravel, iron and steel, lumber, coal, and chemicals, for example—would cost more.
“One barge can carry as much cargo as 60 trucks, so there’d be a lot more 18-wheelers on the road, too. Plus, using barges helps keep our highways safer and reduces fuel use, air pollution, and the number of tires going to landfills.”
From Fort Loudoun Reservoir, our drop of water will slowly make its way through eight downstream reservoirs—Watts Bar, Chickamauga, Nickajack, Guntersville, Wheeler, Wilson, Pickwick, and Kentucky.
At each dam, it will be used to spin the turbines and generate clean, inexpensive hydroelectric power.
Towns and cities along the river will use it to provide drinking water to their residents.
At various locations, it will be withdrawn for different purposes and then returned to the river for re-use downstream. TVA will use it to cool its coal-fired and nuclear power plants. Waterfront industries will use it to manufacture everything from corn syrup to fertilizers. Farmers will use it to irrigate their crops.
And, all along the way, that same rain drop will help provide habitat for fish and aquatic life; support recreation; provide scenic value to those with homes along the shoreline; and enhance the daily lives of millions of Valley residents.
That’s not the end of the story, of course. Shortly after our rain drop passes through Kentucky Dam, it becomes part of the Ohio River. From there, it’s only a short way to the mighty Mississippi and then on to the Gulf of Mexico and the Atlantic Ocean.
But Bach and his staff are more concerned with the rain clouds gathering over the Tennessee Valley.
TVA river schedulers are on duty 24 hours a day, 365 days a year, continually monitoring weather conditions and water quality data, as well as water availability and demand. They make daily—and sometimes hourly—adjustments in water release schedules based on advanced computer models, state-of-the-art radar technology, and an extensive data collection system including more than 300 rainfall and stream-flow gauges.
It’s a sophisticated process, according to Bach. “Our schedules take into account the total amount of water stored in the reservoir system, the time it takes to move water through the system, and reservoir-specific factors such as storage capacities and seasonal operating guides.”
But there’s nothing complicated about the goal. “We try to make every drop of rain count. Day or night, rain or shine, our job is to ensure the right amount of water is in the right place at the right time and at the right quality and temperature for the benefit of everyone in the Tennessee Valley.”