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August 2, 2010

In this issue:
Rain and runoff
Reservoir elevations
Reservoir operations
Project updates
In answer to your questions about tailwater fishing
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

The rainfall deficit in the Tennessee Valley continues to climb. In the eastern Valley, rainfall for the year totaled 24 inches at the end of July, which is 7.4 inches below normal. A few heavy downpours brought temporary relief to some areas in recent weeks. But these events were highly localized, slamming some neighborhoods and missing others entirely, as is typical in summer.
 
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

Eastern Valley rainfall for the year to date is 76 percent of normal.

Runoff (the amount of water that reaches the river system when it rains instead of being absorbed into the ground) is currently 91 percent of normal in the eastern Valley.

 

Reservoir elevations

Most tributary storage reservoirs in the TVA system were within about two feet of their flood guide levels at the end of July, with the exception of South Holston, Watauga, and Blue Ridge.

South Holston and Watauga were 4.1 and 4.9 feet below their flood guide levels, respectively, due to a lack of local rainfall. TVA is conserving water in these reservoirs to bring them into balance with other tributary reservoirs.

TVA began a special deep drawdown on Blue Ridge Reservoir in mid-July. The reservoir will be lowered to an elevation between 1620 and 1630 feet above sea level by November as part of a project to rehabilitate the 79-year-old dam. Get an update on this project below.

 
Tributary reservoir elevations¹

Reservoir

August 1, 2010
Observed Elevation

August 1
Flood Guide Elevation2

South Holston

1724.9

1729.0

Watauga

1954.1

1959.0

Cherokee

1067.1

1069.0

Douglas

989.9

991.5

Fontana

1701.3

1703.0

Norris

1017.8

1020.0

Chatuge

1924.3

1924.9

Nottely

1773.8

1774.9

Hiwassee

1517.6

1519.8

Blue Ridge

1669.2

1685.9

Tims Ford

887.9

888.0

Normandy

873.5

875.0

¹Elevations above mean sea level
²Flood guide elevations show the amount of storage allocated for flood damage reduction during different times of the year. From June 1 through Labor Day, TVA's goal is to meet downstream flow requirements while keeping the reservoir elevation at the dam as close to the flood guide level as possible to support reservoir recreation. During this period, reservoir elevations fall below the flood guide only when rainfall and runoff are insufficient to meet flow requirements. The rest of the year, the primary objective is to keep the reservoir elevations at or below the flood guide to ensure there is enough space in the reservoir to store the rain and runoff from flood events.

 

Reservoir operations

Reservoir levels typically drop in August, and this year will be no exception. In fact, the drop is likely to be even more noticeable than usual, says Chuck Bach, TVA General Manager for River Scheduling.

“Our system flow requirement, which is measured at Chickamauga Dam, goes up each Aug. 1 because river temperatures gradually increase as the summer progresses. Providing more flow in late summer helps to keep the water from becoming too warm, which in turn helps to protect aquatic habitat and water quality. In years with normal rain and runoff, the reservoirs receive enough inflow to make up for much of the water that’s released to meet the higher flow requirement. As a result, there’s less impact on reservoir elevations in those years.

“However, this year we started August with more than a seven-inch rainfall deficit, and with no significant rain in the forecast. That means tributary reservoir elevations will be impacted as we release the minimum amount of water needed to meet our seasonal flow requirement.”

Bach notes that TVA carefully schedules releases to meet two objectives: to balance tributary reservoir elevations and to make the best use of the water.

“TVA has procedures in place to ensure water is drawn from tributary reservoirs equitably. If a reservoir is already well below its guide level due to a lack of local rainfall, for example, TVA tries to conserve water in that reservoir by pulling the needed water from reservoirs that are closer to guide levels.

“Economic dispatch—that is, helping TVA produce power at the lowest cost to reliably serve its customers—is another key consideration,” Bach says.

“During the summer, we don’t release any extra water for power purposes. We cut back on hydroelectric generation, and we rely on cooling towers and reduce generation to stay within permitted temperature limits at our nuclear and coal-fired power plants instead of using river water. But when we have to release water to meet downstream flow requirements, we release it through the turbines at our hydroelectric plants. We also try to time those releases so that the water can be used to generate electricity when power demand is the highest.”
TVA conventional hydroelectric generation for July was only 66 percent of normal.

Current information about rain, reservoir elevations and releases is available from TVA’s River Management page.

 

Project updates

Blue Ridge Rehabilitation Project – TVA began a special deep drawdown on Blue Ridge Reservoir in mid-July. The reservoir will be gradually lowered to an elevation between 1620 and 1630 feet above sea level by November to allow workers to install a new liner in the penstock, which was damaged when the reservoir was refilled after construction in 1931. The penstock is a large underwater pipe which carries water from the reservoir to the turbines in the powerhouse. The project timeline for August calls for completion and initial operation of a dewatering system, which will be used to pipe groundwater around the construction site, and installation of a retaining wall to stabilize the earthen embankment dam while workers dig a hole at the edge of the downstream side of the dam to access the penstock. TVA recently closed a section of North River Road and Old U.S. Highway 76 across the dam for the safety of motorists and construction workers. Read more about the project and sign up for regular e-mail updates.

Ocoee flume repairs – A rock slide on April 28 destroyed a section of the wooden flume which carries water to the Ocoee 2 powerhouse. TVA is continuing to remove the rock that broke loose and bolt the remaining rocks in place. Workers will begin rebuilding the flume in September when this work is complete. As a safety precaution, boaters should not stop or land their boats in the affected section of the river, between Diamond Splitter and Western Flyer rapids, while rock is being cleared and stabilized.

Chickamauga Lock dewatering – The U.S. Army Corps of Engineers closed Chickamauga Lock near Chattanooga, Tennessee, on July 20 for scheduled maintenance to the underwater components of the lock. Water was drained from the structure, and crews are currently checking for cracks and concrete growth, a reaction between ingredients in the concrete that causes the structure to swell and crack. The lock is scheduled to reopen August 16. The existing lock, completed in 1940, has a limited life due to concrete growth. Congress authorized a 110-foot by 600-foot replacement lock at Chickamauga Dam in February 2003. American Recovery and Reinvestment Act funding is being used to complete construction of a cofferdam, a temporary barrier that will create a dry work area, and to fund bridges and other work required for lock construction. The project completion date will depend on Congressional funding.

Kentucky Lock addition – The U.S. Army Corps of Engineers broke ground for construction of a new, larger lock at Kentucky Dam near Paducah, Kentucky, in November 1999. The new lock will be 110 feet by 1,200 feet—twice the size of the existing lock. Work to date has been directed at relocating the existing highway and railway and building a cofferdam, a temporary barrier that will create a dry work area. Construction was delayed by funding constraints but resumed recently with the award of an American Recovery and Reinvestment Act-funded contract for work on the upstream portion of the new lock’s walls. The project completion date will depend on Congressional funding.

Normandy Dam aeration system improvements – TVA is enhancing the system used to improve water quality in the Duck River below Normandy Dam. This system consists of air compressors on the bank which are connected to perforated hosing, called diffuser line, suspended above the reservoir bottom upstream of the dam. Compressed air is pumped through the line, creating oxygen bubbles that are released into the reservoir along the length of the line. TVA is replacing 12,000 feet of existing diffuser line, which has deteriorated since it was installed in 1994, and installing 20,000 feet of new line. The work should be completed in September.

 

In answer to your questions about tailwater fishing

How do I get an advance generating schedule?
You can get the latest water release schedules for TVA dams from our Reservoir Information page. Use the pull-down menus in the shaded box on the right-hand side of the page to choose your reservoir and the type of information you are interested in seeing. For the release schedule, you’ll want to select “Levels (Releases & Elevations).” Then click “View info.” You’ll find information on observed and predicted releases, as well as observed and predicted water levels upstream and downstream of the dam.

Water release schedules are updated periodically throughout the day. Next-day release schedules are usually available by 6 p.m. of the current day.

Water release schedules also are available by calling our automated reservoir information line: 632-2264 in the Knoxville area; 751-2264 in the Chattanooga area; 386-2264 in the Muscle Shoals area; and 1-800-238-2264 from all other locations. If you are hearing-impaired, call 1-800-438-2264. An automated recording will guide you to the information you need. Get detailed information about obtaining reservoir information by phone.

I need more than a day’s notice to plan a fishing trip. Can I get a release schedule any earlier?
The earliest you can get a release schedule is after 6 p.m. the evening before. This is primarily because unanticipated changes in the weather often result in changes to the release schedule. If more rain than predicted materializes, we may need to cut back on generation at some locations to prevent downstream flooding. At other locations, we may need to increase generation in order to move more water through the reservoir system before the rainfall event arrives.

Changes in the demand for electricity also may cause last-minute changes in the release schedule. Since hydropower can be brought online almost instantaneously, it is especially valuable during peak power demands. As demand for power fluctuates during the course of the day, hydro generation has the ability to follow that demand.

Finally, it’s helpful to be able to rely on hydropower when mechanical problems arise with other generating sources. If a large coal or nuclear generating unit experiences an unplanned outage, hydro can help make up the difference.

Actual discharges sometimes differ from published release schedules for the same reasons.

We make every effort to provide timely and reliable release schedules, but there is an ongoing need for flexibility in order to maximize the public benefits from the reservoir system.

Why don’t you generate at night so we can fish in the tailwater during the day?
While we regret the inconvenience to anglers, we are committed to keeping power rates as low as possible which requires us to generate hydroelectricity—our lowest cost energy source—when demand is highest. Although the generation (megawatt hours) would be the same whether the water is released in the daytime or nighttime, the value of the generation varies greatly. In the summer, it is not unusual for hydro generation to be worth several times the value during the peak load hours, which occur during the hottest part of the day, as compared to low load hours at night. If we were to shift hydro generation to the nighttime, we would need to purchase electricity from another supply or use other more costly sources of energy, such as combustion turbines, to meet peaks in demand during the day. This would affect the rates you pay for electricity.

In addition, we are committed to meeting specific flow requirements below our dams to protect water quality and aquatic habitat. The required water is generally discharged through the turbines at specified intervals in order to maximize its public value.

Why can’t you be more specific about how many and which generators you’ll be operating?
Plant-specific generation schedules can change with very little notice as a result of unanticipated maintenance outages or special operations, so it would be difficult to provide reliable information about which generators will be operating. Moreover, that information is protected for competitive reasons. If TVA were to release it publicly, other power suppliers could use it to calculate how much power we are able to generate, which could affect TVA's ability to negotiate the best price if we need to buy power on the open market or if we have power to sell. This, in turn, could affect TVA’s efforts to keep power rates as low as possible.

When you start generating, how fast does the water travel downstream? How long does it take for flows to reach minimum when the generators are turned off?
It depends on the number of generators that are operating and a variety of other factors, including the amount of energy the generators are required to produce, how long it’s been since the last generation period, and river flow dynamics, which are unique to each tailwater. A general rule of thumb, however, is that the water released when power is being generated travels at a speed of approximately two to three miles per hour. The water near the dam will drain down to a minimum flow in about an hour and a half, with higher flows persisting longer further

 


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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