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November 1, 2010

In this issue:

Rain and runoff
Reservoir elevations
Reservoir operations
Hydropower—clean, reliable, and economical
Blue Ridge Dam rehabilitation project update
Stay away from dangerous waters near dams
More TVA information

TVA provides monthly updates on the operation of TVA-managed reservoirs by e-mail. To sign up for future updates, provide feedback, change your e-mail address, or have your address removed from this distribution list, please send an e-mail request to reservoirupdate@tva.com.

 

Rain and runoff

Rain for the first three weeks of October was only 24 percent of normal, but a series of fast-moving storms on Oct. 25 and 26 dumped two to four inches of rain across the Valley. The month ended with a rainfall total of 2.89 inches, which is 97 percent of normal.

Rainfall in the eastern Tennessee Valley for the year totaled 34.63 inches at the end of October, which is 7.47 inches below normal. Runoff (the amount of water that reaches the river system when it rains instead of being absorbed into the ground) was 86 percent of normal in the eastern Valley.

Eastern Valley Rainfall

Month

Observed rainfall

Normal rainfall

Percent of normal

January

4.51

4.6

98

February

2.68

4.23

63

March

2.79

4.82

58

April

2.69

4.17

65

May

4.50

4.23

106

June

2.91

4.28

70

July

3.96

4.97

80

August

4.01

4.28

94

September

3.68

3.38

109

October

2.89

2.99

97

Total
(year to date)

34.63

42.10

82

 

Reservoir elevations

The elevations of tributary storage reservoirs gradually dropped through the month of October as TVA continued the annual drawdown to winter flood-damage-reduction levels. Most reservoirs were at expected levels on Nov. 1, ranging from an average of 14 feet above Jan. 1 target levels on Douglas, Fontana, Hiwassee, and Tims Ford to an average of four feet above Jan. 1 target levels on South Holston, Cherokee, Norris, Chatuge, Nottely, and Normandy.

As in previous months, Watauga Reservoir was the exception. It fell below its winter flood-damage reduction level the end of August because there wasn’t enough rain in the surrounding watershed to compensate for the water released to meet downstream flow requirements. Because Watauga is still below its winter flood-guide elevation, TVA is continuing to limit releases to conserve water in Watauga, which may result in some increase in the reservoir’s elevation depending on local rainfall.

Blue Ridge Reservoir is also a special case. TVA began a deep drawdown on Blue Ridge in mid-July. The reservoir is being held at an elevation between 1620 and 1630 feet above sea level—compared to its normal winter flood-damage-reduction level of 1668—as part of a project to rehabilitate the 79-year-old dam. Get an update on this project below.

Reservoirs along the main Tennessee River—Fort Loudoun, Watts Bar, Chickamauga, Nickajack, Guntersville, Wheeler, Wilson, Pickwick, and Kentucky—were all within their normal operating ranges on Nov. 1.

Tributary Reservoir Elevations¹

Reservoir

Nov. 1, 2010
Observed Elevation

Jan. 1
Flood Guide Elevation2

South Holston

1712.1

1708

Watauga

1947.7

1952

Cherokee

1050.7

1045

Douglas

969.5

954

Fontana

1670.9

1653

Norris

1004.7

1000

Chatuge

1920.1

1918

Nottely

1766.3

1762

Hiwassee

1497.4

1485

Blue Ridge

1625.1

1668

Tims Ford

885.8

873.1

Normandy

868.5

864

1 Water elevation at the dam in feet above mean sea level
2 Flood-guide elevations show the amount of storage allocated for flood damage reduction during different times of the year. The amount of storage varies with the potential flood threat. Flood-guide elevations are lowest from Jan. 1 through mid March because winter storms are generally larger, occur more frequently, and produce more runoff. Flood-guide elevations increase between mid-March and June 1 as the risk of flooding decreases. They are highest from June 1 through Labor Day to support summer reservoir recreation. After Labor Day, TVA begins the unrestricted drawdown to Jan. 1 flood-guide elevations.

 

Reservoir operations

From September through December, TVA reservoir operations are focused on lowering reservoir elevations to winter flood-damage-reduction levels as efficiently as possible.

“As we release water to create the flood-storage space we need in winter, we try to get the most the value we can from it,” says David Bowling, manager of TVA’s River Forecast Center in Knoxville. “That means releasing it through the hydroelectric turbines at TVA dams—preferably on days and at times when power demand is highest.”

He says a lot of factors are considered in scheduling water releases, including the long-term weather forecast.

“For the next three months, TVA’s meteorologist is calling for above-normal rain in the western Tennessee Valley and dry conditions in the eastern portion,” Bowling says. “Based on that forecast, we are scheduling releases to conserve water in the tributary system so that we can use it to generate hydroelectric power as the weather turns colder in the weeks ahead while ensuring that we maintain adequate flood storage space throughout the reservoir system.”

Bowling reminds reservoir users that they can get a general idea about what to expect in terms of winter reservoir elevations by looking at the operating guide for their reservoir on TVA’s public website.

Go to TVA’s Reservoir Information page and then click on the down arrow in the “Select a reservoir” box. Choose a reservoir from the drop-down list and click on the “View info” button. You’ll see a page with current operating information for that reservoir. Click on the “Operating guide” link on the right side of the page.

“If you’ve selected a tributary flood storage reservoir, you’ll see a graph with a gray band labeled ‘Expected elevation,’” says Bowling. “Based on computer simulations using more than 100 years of historical rainfall and runoff data, you can expect your reservoir to be in the shaded area an average of eight out of 10 years on any given date.”

For main-river reservoirs, look for the shaded band labeled “Normal operating zone.”

 

Hydropower—clean, reliable, and economical

This article continues our series on the many ways the Tennessee River system touches our daily lives. In previous issues, we talked about the benefits of river transportation and flood-damage reduction. In upcoming issues, we’ll highlight water supply, water quality, and recreation benefits.

TVA’s hydroelectric plants generate an average of about 14.5 billion kilowatt-hours of electricity annually, enough to serve just over one million homes for a year.

But those numbers don’t begin to reflect its value, says Sammy Sweetland, general manager of Hydro Production at TVA.

“Every kilowatt of electricity that can be produced by hydropower means just that much less need for relying on other generating assets which have higher fuel and operating costs and more impact on the environment.”

Hydroelectric plants are cheaper to operate than nuclear or fossil-fuel plants because they don’t use any fuel—except for the water flowing through the dam, which can be reused for other purposes. Plus, hydropower is an extremely efficient source of energy. Modern hydropower plants can convert about 90% of the available energy into electricity, while fossil-fuel plants, on average, are only about 40% efficient.

Hydropower has other advantages that help to keep rates down, says Sweetland.

“While some of our larger coal-fired plants may take anywhere from 12 to 24 hours to reach full capacity from initial start-up, our hydro plants can go from shutdown to full load in just a few minutes. That’s important when there is a rapid increase in electricity demand or if a fossil or nuclear unit in the TVA system suddenly goes off line. Hydro is there to make up the shortfall. If there’s a sudden drop in demand, we also can make an immediate adjustment to our hydro generation, which minimizes the need for expensive ‘turn downs’ at our fossil and nuclear plants.

“Our hydro plants add flexibility to TVA’s power system—and, in this line of business, flexibility translates into cost savings.”

Sweetland says having a variety of fuels with which to generate electricity is important, too. “TVA’s generation mix—coal, nuclear, natural gas, plus hydroelectric and other renewable energy sources such as sunlight, wind, and landfill gas—reduces the region’s dependence on a single source of power production. That allows TVA to respond to fluctuations in price resulting from changing market supplies and prevents the possibility of being held ‘hostage’ to any single high-cost source.”

Hydro also is clean energy, according to Sweetland. “It doesn’t produce any waste products, and it is emissions free. It doesn’t contribute to air pollution, acid rain, or ozone pollution. In fact, the use of hydropower makes it possible for TVA to burn less fossil fuel—coal, oil, and gas—which avoids the release of additional carbon dioxide into the air.”

No energy source is perfect. Hydropower can have an impact on aquatic life and habitat. But Sweetland says TVA has taken extensive steps and spent millions of dollars to minimize those impacts.

“Since the early 1990s, TVA has spent about $60 million to address two environmental problems related to hydropower production: dry riverbeds that result when hydro generation is shut off and low concentrations of dissolved oxygen in the water released through the dam during electricity generation. We’ve solved those problems through a combination of approaches, including changes in our operations and installing equipment to maintain a minimum flow and add oxygen to the water. Studies show that these improvements are making a real difference. We’ve seen an increase in the number and diversity of fish and insects in below TVA dams, as well as a significant growth in tailwater fishing, which is good for the local economy.”

Find out what TVA is doing to protect water quality at dams near you.

TVA’s hydroelectric generating system consists of 109 conventional hydroelectric generating units at 28 sites along the Tennessee River and its tributaries and at one site on the Cumberland River (Great Falls). TVA also operates a four-unit pumped-storage hydroelectric plant at Raccoon Mountain near Chattanooga.

A conventional hydroelectric plant produces electricity using the force of water stored behind a dam to spin the blades of a turbine. When the water is released through the dam and spins the turbine, it turns a metal shaft which goes up to an electrical generator, a motor that produces electricity. As the shaft turns, it causes the generator to rotate, producing electricity. After passing through the turbine, the water flows back into the river, called the tailwater, on the other side of the dam.

A pumped-storage plant uses two reservoirs—one located at a much higher elevation than the other. During periods of low demand for electricity, such as nights or weekends, energy is stored by reversing the turbines and pumping water from the lower to the upper reservoir. The stored water can later be released to spin the turbines and generate electricity as it flows back into the lower reservoir.

Learn more about how conventional and pumped-storage plants work.

Fast facts

  • During the winter, TVA hydro plants can produce up to 5,193 megawatts of electricity. This includes 3,540 megawatts of conventional hydroelectric generation and 1,653 megawatts from Raccoon Mountain.
  • Conventional hydroelectric plants range in capacity from the four-unit, 11-megawatt Wilbur plant to the 21-unit, 663-megawatt Wilson plant.
  • The oldest of TVA’s conventional plants, Ocoee 1 and Wilbur, began producing electricity in 1912. The newest, Tims Ford, came online in 1972.
  • TVA purchases hydroelectric generation from eight U.S. Army Corps of Engineer plants on the Cumberland River system and from four Alcoa Power Generating, Inc., plants on the Little Tennessee River system.
  • TVA’s hydroelectric system is one of the largest automated systems in the world. The transition from a manual to a fully automated system took seven years to complete. The last plant, Ocoee No. 2, was brought on line as a fully automated plant in 2005.

 

Blue Ridge Dam rehabilitation project update

The deep drawdown of Blue Ridge Reservoir is essentially complete. The reservoir reached an elevation of 1630 feet above sea level—the elevation at which workers can safely enter and repair the penstock—in early October. This allowed personnel to enter the penstock through the powerhouse entry point to assess the work that needs to be done in preparation for replacing the penstock liner. Overall, there has been little change in the condition of the penstock since TVA’s last inspection in 2003, which is good news. High pressure cleaning of the penstock is in progress and going well.

Progress also is being made on the construction of a retaining wall which will hold the adjacent soil in place during excavation to the penstock. The vertical steel beams for the wall have been erected, and workers are in the process of attaching the horizontal timbers that will bear the soil pressure. Replacement of the penstock liner is expected to begin in January.

TVA will continue releasing water as needed to keep the reservoir elevation between 1620 and 1625 feet so that work inside the penstock can continue even if heavy rain causes the reservoir elevation to rise.
Workers have finished removing the rip rap from the upstream face of the dam and will begin putting down new rip rap as soon as grading of the area is complete. This will mean more construction traffic on the dam as trucks bring in rock from the quarry—which will make it more important than ever to use caution when traveling in the area. 

Daily monitoring of dam instrumentation for dam safety is progressing smoothly, and work to stabilize the water intake tower will begin soon.

Read more about the project and sign up for regular e-mail updates.

 

Stay away from dangerous waters near dams

A recent boating incident at Wheeler Dam in Decatur, Ala., is an important reminder that water being discharged from powerhouses and spillways on the Tennessee River system can be extremely dangerous.

Three fishermen were pulled to safety Wednesday, Oct. 20, and lucky to be alive several hours after their fishing boat was caught in turbulent water near a hydro-generating unit at Wheeler Dam. The boat sank the previous night at the base of the dam’s powerhouse.

Wheeler Dam is equipped with a tailwater warning system. When activated, warning horns and strobe lights warn of the rapidly rising water and turbulence. Signs also warn boaters of the dangers.

“To be safe, boaters and anglers should not get close to the base of the dams,” says John McCormick, senior vice president of TVA River Operations. “It is a very dangerous place to be. An enjoyable day of fishing can quickly turn tragic if boaters and fisherman don’t heed the warnings and then get caught in rising, turbulent waters that are being discharged from below the dams.”

Anyone who sees unsafe activities can contact TVA Police at 800-824-3861 or their local law-enforcement agencies.

More information about avoiding the dangers surrounding dams, locks and powerhouses is available at www.tva.com/river/hazwater.

 


Get more information on TVA.com

The links below will take you to reservoir-related information on TVA’s website.

TVA’s reservoir operating policy:  Learn how TVA manages the flow of water through the Tennessee River system to provide navigation, flood damage reduction, power supply, water quality, water supply, recreation, and other benefits.

Reservoir information:  Get detailed information about individual reservoirs, including observed and predicted elevations and releases at TVA dams, reservoir operating guides, water quality improvements, fish population survey results, and more.  To check reservoir information from your cell phone or other mobile device, go to http://m.tva.com.

Rainfall and stream flows:  Get the latest information on daily rainfall and stream flows across the Valley.

Recreation release schedules:  View the 2010 schedule for water releases for rafting, kayaking, and canoeing below these TVA dams:  Apalachia, Ocoee No. 1, Ocoee No. 2, Ocoee No. 3, Norris, Watauga/Wilbur, and Tims Ford.

Map of TVA reservoirs and power plants:  Our interactive map is your guide to the entire TVA power system, including fossil and nuclear plants, dams and reservoirs, and visitor centers.  You’ll find interesting facts about each facility and learn how they work together for the purposes of power supply, river management, and economic development.

Water supply FAQs:  Get answers to frequently asked questions about obtaining a water intake permit, improving water quality around intakes, inter-basin transfers, and more.

Dangerous areas around TVA dams:  If you like fishing or enjoy swimming and boating on TVA-managed reservoirs, you need to be aware of the possible hazards around dams, locks, and powerhouses.

How to lock through:  Find out what you need to do to safely approach a navigation lock, secure your boat in the lock chamber, and exit the lock.

Reservoir health ratings:  See the latest monitoring results for TVA-managed reservoirs.

Campgrounds and day-use areas:  Get information here about campground fees and amenities as well as picnic pavilion reservations.

TVAkids.com:  TVA’s got a Web site just for kids!  Learn about how TVA makes electricity, reduces flood damage, protects wildlife, and more.  There’s a section for teachers, too.

TVA Heritage:  Read about the people who founded TVA, shaped its purpose, and built its power plants.  TVA Heritage offers fascinating glimpses of the agency’s 76-year history.

Get more information by phone

For the latest information on reservoir elevations and stream flows, call TVA’s Reservoir Information Line from a touch-tone phone:

  • From Knoxville, TN:  865-632-2264
  • From Chattanooga, TN:  423-751-2264
  • From Muscle Shoals, AL:  256-386-2264
  • From all other locations:  800-238-2264 (toll-free)

For answers to questions on how your reservoir is operated, call TVA River Operations at 865-632-6065.

For answers to questions about recreation, permitting procedures, reservoir land management plans, and other environmental issues, call TVA’s Environmental Information Center at 1-800-882-5263.

 
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