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TVA River Neighbors
 

March 7, 2012

In this issue:
Rainfall and Runoff
Current Reservoir Conditions/Operations
Doing Whatever it Takes: Ensuring Dam Safety through Monitoring and Maintenance
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

After fairly regular rainfall during late 2011 and for most of the month of January, the month of February turned a bit dry. Rainfall for the part of the Valley above Chattanooga was 74% of normal, and 61% of normal below Chattanooga. Basin-wide, rainfall for the month of February totaled 70% of normal.

Runoff more or less mimicked the rainfall amounts. For the month of February, runoff for the Tennessee Valley watershed was 71% of normal—with totals coming in at 80% of normal above Chattanooga and 63% of normal for the part of the Valley below Chattanooga.

 

Current Reservoir Conditions/Operations

All TVA tributary reservoirs are either at or near flood guide levels—with one exception. Norris is currently four and a half feet above flood guide, and according to Senior Manager of Forecast Operations Tom Barnett, that's no surprise. "Sometimes you'll see levels on a particular reservoir that might appear to be an anomaly," he says. "But the fact is, the Norris watershed got pounded in late February by a large localized thunderstorm that delivered over an inch of rain. Because this storm just kind of 'sat there' for a while, the precipitation was concentrated in that one spot, while the watersheds adjacent to Norris were dry."

In terms of overall elevations, Barnett says they're right where they should be: "The main-river reservoirs are all within or near their normal operating ranges and the rainfall we've had has kept us in a good position to begin the spring fill on the tributary reservoirs. Unless things get unexpectedly dry, we should be in good shape to achieve our June 1 flood guide levels."

Tributary Reservoir Elevations
Reservoir

March 1, 2012
Observed Elevations1

March 1
Flood Guide2

South Holston

1711.1

1710.4

Watauga

1952.5

1952.0

Cherokee

1045.8

1045.0

Douglas

955.6

954.2

Fontana

1653.2

1653.0

Norris

1004.5

1000.0

Chatuge

1917.9

1918.0

Nottely

1761.8

1762.0

Hiwassee

1485.1

1485.0

Blue Ridge

1672.3

1672.5

Tims Ford

877.3

877.8

Normandy

864.4

864.2

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.

Filling has already begun on South Holston and Douglas, and the majority of tributary reservoirs are scheduled to begin filling by mid-March. Why does TVA start the filling process earlier on some, than at others? "It has to do with rainfall received and the individual watershed characteristics," explains Barnett. "At the same time that we're looking ahead to the recreation season, we're always conscious of maintaining an acceptable flood risk reduction capacity."

And once again, everything depends upon the weather. Filling the tributary reservoirs on schedule becomes difficult without plentiful spring rains. On the other hand, a widespread and lingering rainfall event can present challenges, in terms of flood storage.

No matter how wet or dry it is, however, Barnett and his co-workers are never in a position of not knowing how to proceed. "After the spring fill begins, it's all about conserving every drop of water we possibly can," he says. "That means releasing the minimum flow requirements—for things like downstream aquatic habitat, water quality, etc.—and nothing more. The challenges are different for each time of year, but there's no 'ad-libbing' when it comes to operating the Tennessee River system. The guidance is there and we follow the policy."

 

Doing Whatever it Takes:
Ensuring Dam Safety through Monitoring and Maintenance

Yes, there are a wide variety of important benefits provided by TVA's system of dams and reservoirs: everything from hydroelectric power to navigation to recreation. But in order for any of those benefits to be realized, the basic function and structural integrity of the dams themselves has to be ensured—first and foremost. At least, that's the way Jennifer Dodd sees it.

As Senior Manager of TVA's Non-Power Assets Program, Dodd is responsible for the monitoring and maintenance required to keep the dams working as they were designed to do. "Ensuring the safety of the public is job number one," she says.

Norris
TVA employees developed a Portable Datalogger to collect information at specific time intervals from the area around dams. Data can be obtained at any time of day or night, as well as in all kinds of weather conditions—and can be transmitted directly to a central database through cell phone connections.

The effort begins with monitoring, which is accomplished by two different methods—instrumentation and inspection. Each is necessary when it comes to accurately determining the condition and behavior of a dam. "We employ a wide range of sensitive instruments to tell us what's going on," says Dodd. "Some are providing data automatically, while others are manually read. After collection, this information is extensively evaluated and analyzed. We're not just looking at 'point in time' conditions; by comparing results with historical data, we're able to monitor long-term trends and assess performance over time."

Norris
Rope access inspection team members take a close look at the spillway gates at Fontana Dam. Several TVA crews travel to dams across the Valley, conducting site inspections that help provide meaningful data.

Inspection provides information that can't be obtained by instrumentation. TVA's dams are inspected on a cyclical schedule, by both engineering and site personnel. Whether monthly "walk-downs" or comprehensive formal inspections conducted every five years, these assessments are a way to "get up close and personal" with the dams. "Even the most sophisticated instruments are sometimes no match for the eyes of a trained professional," says Dodd. "We are committed to conducting thorough inspections, and sometimes that means turning to unconventional means. We've used everything from remotely-controlled 'crawlers' to teams of divers to crews of folks who hang off ropes to perform inspections. Even a groundhog hole close to a TVA dam is noted and repaired!"

Norris
After a sinkhole opened up on the Boone Dam reservation, crews determined its extent and then backfilled the opening and compacted the soil around it. Whether preventative or corrective, maintenance is an important part of TVA's efforts to ensure dam safety.

Monitoring is only half the story, though. Ensuring dam safety also requires a robust maintenance program. "Some people may think that it's all about fixing problems that occur," says Dodd. "And certainly there is attention focused on developing and implementing solutions to issues that have been identified through instrumentation and inspection. We refer to that as 'corrective' maintenance. But just as important is what we call 'preventative' maintenance. Whether that means making sure spillway gate wheels are greased or keeping vegetation mowed to promote visibility, we pride ourselves on doing the things it takes to make sure that problems don't arise in the first place."

In summary, Dodd addresses TVA's focus on dam safety: "With layers upon layers of safeguards—processes and procedures designed specifically to gather and analyze data and then respond swiftly and effectively to the findings obtained through monitoring and inspection—our stakeholders can feel very confident that we are doing whatever it takes to keep these dams safe."


Fast Facts

  • TVA's River Operations organization conducted 1,636 safety inspections of conventional dams during 2011. (Other inspections were performed by other parts of TVA, for additional assets—such as impoundments, ponds, and dikes.)

  • Approximately 5,100 instruments are used to monitor conditions at TVA's conventional dams; 3,600 are automated and 1,500 are manually-operated.

  • A separate and independent organization (TVA's Dam Safety Governance Program) provides oversight for the work performed by TVA's Non-Power Assets group related to dam safety and conducts objective assessments of its compliance efforts.

 


 

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.