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TVA River Neighbors
 

September 7, 2011

In this issue:
Rainfall and runoff
Current reservoir conditions
Reservoir operations
Power plants, river temperatures and reservoir releases

TVA briefs Blue Ridge residents on dam rehabilitation project
TVA improves recreational opportunities at Wilbur and Watauga Reservoirs
More TVA information

TVA provides these monthly updates on the operation of the reservoir system by email. We sincerely welcome your comments and questions. To provide feedback, sign up for future updates, change your email address, or be removed from this distribution list, please contact riverneighbors@tva.com.

 

Rainfall and Runoff

Rainfall in July for the part of the Valley above Chattanooga was 75% of normal, and August was even drier: just 43% of normal.

Predictably, runoff (the amount of water that reaches the river system when it rains instead of being absorbed into the ground) was impacted by the continued dry conditions, dropping from 76% of normal in July to 41% of normal in August.

All of the large storage reservoirs in the Tennessee River system are located upstream of Chattanooga so rainfall and runoff in this part of the basin has an impact on reservoir conditions Valley-wide. A drop of water that falls on one of these tributary reservoirs can be used over and over again as it flows through as many as 12 downstream reservoirs.

Note: As we posted this issue of TVA River Neighbors, heavy rain was continuing to fall across the Tennessee Valley.  The region received more than four inches of rain over the Labor Day weekend with a continued chance of showers and thunderstorms in the forecast through the week.  We’ll update you on the impact of this record-setting rainfall event on reservoir conditions in our next issue.

 

Current reservoir conditions

Water levels in most of the large tributary reservoirs dropped significantly in August due to a combination of factors, says David Bowling, senior manager of TVA’s River Forecast Center.

“Our system flow requirement goes up each year on August 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. But, this year, July and August were hot and dry so the effect on reservoir elevations was more noticeable.”

Most of the large tributary reservoirs were from five to 12 feet below flood guide levels on September 1. The exceptions were Chatuge, which was two feet below its flood guide, and Nottely, which about 4.6 feet above its flood guide.

Nottely is above flood guide because the generating unit had to be taken out of service last February. TVA continued to provide minimum flows through the spillway at the dam while the unit was repaired. But, without the generating unit to pass water, reservoir elevations were higher than target levels all summer.  The generating unit at Nottely was returned to service on September 2.  TVA is running the unit between 12 and 18 hours a day, and the reservoir elevation is expected to return to normal by October.

All the main-river reservoirs are within their seasonal operating ranges.

Current reservoir conditions
Reservoir
September 1, 2011
Observed Elevation1

September 1
Flood Guide2

January 1
Flood Guide2

South Holston

1719.7

1729.0

1708

Watauga

1950.7

1959.0

1952

Cherokee

1057.5

1069.0

1045

Douglas

980.7

991.5

954

Fontana

1690.0

1703

1653

Norris

1007.7

1020.0

1000

Chatuge

1921.4

1923.4

1918

Nottely

1776.7

1772.1

1762

Hiwassee

1507.9

1513.2

1485

Blue Ridge

1675.0

1682.4

1668

Tims Ford

886.8

888.0

873.1

Normandy

873.3

875.0

864

¹Elevations above mean sea level, as of 12:01 a.m. on this date

²Flood guide levels show the amount of storage allocated for flood damage reduction during different times of the year. During the summer, TVA's goal is to meet downstream flow requirements while keeping the reservoir level at the dam as close to the flood guide level as possible to support reservoir recreation. From June 1 through Labor Day, reservoir levels fall below the flood guide only when rain and runoff are insufficient to meet flow requirements. During the rest of the year, the primary objective is to keep the reservoir level 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

After the Labor Day weekend, tributary reservoir elevations begin dropping at a faster rate. David Bowling, senior manager of TVA’s River Forecast Center, explains why.

“From June 1 through Labor Day, TVA restricts the drawdown of tributary storage reservoirs to provide higher levels for recreation,” he says. “During that period, under normal operations, just enough water is released from these reservoirs to meet downstream flow requirements. TVA generates hydroelectric power with the water released to meet those requirements, but we don’t release any extra water solely for the purpose of hydro generation.

“That doesn’t mean that reservoir levels stay steady. If there isn’t enough rain to replace the water released to meet minimum flow requirements, levels will drop. But the restrictions on releases help to provide the higher pool levels that everyone wants to see in the summer.

“After Labor Day, flow restrictions are lifted. We start releasing water from tributary storage reservoirs at a faster rate with the goal of lowering water levels to Jan. 1 flood-damage-reduction levels as efficiently as possible.

“We balance a lot of different interests in operating the reservoir system but, beginning in September, our focus is on lowering the level of flood-storage reservoirs to make room to hold the runoff produced by winter storms. This enables us to provide the flood reduction benefits that TVA’s system of dams and reservoirs was designed to provide.”

Main-river reservoir operations
Main-river reservoirs don’t fluctuate as much as tributary reservoirs because they have less storage space and because of navigation requirements. Their drawdowns are staggered from July through November primarily to ensure that the released water can be used efficiently, generating electricity as it runs through the turbines at as many as nine dams downstream.

The seasonal drawdown begins after the 4th of July weekend on Kentucky Reservoir; following the Labor Day weekend on Chickamauga, Guntersville, Wheeler and Pickwick; and on November 1 on Fort Loudoun and Watts Bar.

 

Power plants, river temperatures and reservoir releases

TVA’s coal-fired and nuclear power plants are located alongside a river for a reason: they rely on river water to help dissipate the heat left over after making electricity. After flowing through a plant’s cooling system, the water is discharged back into the river.

Each of these plants operates under a state-issued discharge permit that specifies water temperature limits for the river. These permits protect aquatic life in the river, which can suffer if water temperatures get too high.

BrownsFerry

TVA has received a number of calls in recent weeks from people who are concerned that TVA is providing special releases of water from tributary reservoirs to help comply with water temperature limits at downstream power plants. Paul Hopping, a technical specialist on the Operations Evaluation staff in TVA’s River Scheduling organization, says this isn’t the case.

“From June 1 through the Labor Day weekend, our reservoir operating policy allows us to release only enough water to meet very specific downstream flow requirements. We try to release this water through the hydro turbines at TVA dams at times when it is most valuable to the power system, but we don’t release any extra water for thermal compliance.”

That can mean reducing generation to stay within permitted temperature limits at TVA’s coal-fired and nuclear power plants.

Hopping points to a recent example.

“In late July and early August, TVA reduced power at Browns Ferry Nuclear Plant to stay within the discharge permit issued by the state of Alabama. At one point, all three units were reduced to a power level of about 50 percent.

“Our water temperature forecasting model predicted a period of high river temperature during this time, prompting the decision to reduce power at Browns Ferry to avoid exceeding the 90°F downstream temperature limit set by the permit.”

 

BFN Tower

 

 

 

 

That’s a scenario TVA tries to avoid because the power often has to be replaced from sources on the open market, which is expensive.  Releasing the water needed to meet downstream minimum flow requirements in a strategic manner can help.

“By operating hydro plants in a steady fashion, we can reduce adverse mixing in the affected reservoirs, which helps preserve cooler water in the bottom of the main-river channel,” explains Hopping.

TVA is working on a multimillion-dollar project to build a seventh, state-of-the-art cooling tower and upgrade four of the six existing cooling towers at Browns Ferry.

The new cooling tower is much larger than the existing cooling towers. Once in operation, it will significantly increase the plant’s ability to lower the temperature of water before discharging it into the river and decrease the likelihood of having to reduce power on one or more units.

 

TVA briefs Blue Ridge residents on dam rehabilitation project

 

People meeting

 

 

Blue Ridge area residents had a chance to learn about TVA’s progress in rehabilitating Blue Ridge Dam and get answers to their questions at a Community Day event hosted by TVA on August 13.

 

More than 200 Blue Ridge area residents accepted TVA’s invitation to see the progress at Blue Ridge Dam for themselves at a Community Day event on August 13. Residents were able to walk out on the dam and talk with project specialists about milestones that have been met and what’s to come in the months ahead.

TVA’s Blue Ridge Dam began generating electricity again on July 11, after a year-long repair project on the penstock, the large pipe that carries water from the reservoir to the turbines in the powerhouse.

The rehabilitation work, to meet more rigorous safety standards, began in July 2010 with the drawdown of the reservoir.  On September 1, the reservoir was only about eight feet below target levels after being as low as 65 feet below flood-guide levels over the past year.

The project had three components: installing a new liner in the penstock, stabilizing the water intake tower above the dam, and adding rock to the upstream and downstream faces of the dam.

The first phase, installing 500 feet of the 1,000 feet of steel liner in the penstock, was completed March 24 and allowed the reservoir to begin refilling. The new liner repaired damage to the penstock that occurred in 1931 when the reservoir was filled after the dam was completed.

In the second phase, TVA drilled 60-foot holes to secure six multi-strand anchors in the bedrock beneath the water-intake tower to ensure it can withstand an extreme earthquake. That work was completed May 31.

The third phase, adding rock to stabilize and strengthen the dam, is partially complete. TVA has finished the rock placement on the upstream face of the dam and is now working on the downstream face. This work is expected to be finished in summer 2012.

A dissolved-oxygen system, which allows oxygen to be injected into the reservoir to improve downstream water quality, also has been replaced. The system helps support a thriving trout population.

“Performing this work in three phases allows us to refill the reservoir and add oxygen to the water at the same time we finish the work, benefitting fishermen and boaters,” says John McCormick, TVA’s senior vice president of River Operations.

 

TVA improves recreational opportunities at Wilbur and Watauga Reservoirs

Fishing near Wilbur Dam is now easier for all anglers, including those with disabilities.

 

Photo of new concrete ramp at Wilbur Reservoir

 

 

The concrete ramp shown here provides universal access to fishing along the Wilbur Reservoir.

 

In March, TVA completed a concrete ramp along the rocky banks of the Wilbur Reservoir near Elizabethton, Tenn. The walkway provides universal access to a popular fishing spot for trout drawn to the reservoir’s cool waters. 

TVA also installed a new parking lot across the road to serve the walkway.

In addition, three universally accessible campsites have been added to the nearby Watauga Reservoir campground, bringing the total number of campsites there to more than 30. The Wilbur and Watauga reservoirs are located just three miles from each other.

Valerie McLeod, TVA’s Disability Program manager, says these improvements in accessibility conform to new national guidelines.

“As a federal agency, TVA has a commitment to ensure that new construction in our recreation areas throughout the TVA region are constructed in such a way that they’re accessible to those with disabilities,” McLeod says.

“We tried to think of every possible scenario with this project,” adds Jerry Fouse, a recreation management specialist for TVA’s Environment & Technology organization. “We wanted everybody to be able to enjoy Wilbur Dam and the other recreation facilities.”

 

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.

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

Recreation release schedules: View the 2011 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, Upper Bear Creek 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 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.