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TVA River Neighbors
 

October 6, 2011

In this issue:
Rainfall and Runoff
Current Reservoir Conditions
Reservoir Operations
Ocoee #1: Celebrating a Century of Hydropower
Blue Ridge Project Update
New Dam Safety Warning Systems
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

The month of September was considerably wetter than average. More than three-quarters of the rainfall total for the entire month fell in just the first week, in the form of remnants from Tropical Storm Lee.

That weather system, which impacted parts of the Valley for portions of three days (September 4-6), broke some historic records. The single-day rainfall total for Chattanooga was shattered; the previous level was exceeded by more than an inch. And TVA’s gauge at Charleston (just northeast of Cleveland, Tennessee) recorded a whopping 13.2 inches of rainfall that fell in just two days.

For the part of the Valley above Chattanooga, rainfall for the month was 180% of normal, which helped considerably in getting us closer to normal rainfall levels for the 2011 calendar year. After September’s rains, we currently stand at 97% of normal.

In terms of runoff, the area above Chattanooga received one and a half times the normal amount for the month of September—a very welcome development after an August which was only 41% of normal. For the calendar year, runoff is now at 98%.

 

Current Reservoir Conditions

Talk about timing. The remnants of Tropical Storm Lee blew into the Valley on the last day of the summer compliance season, bringing all that rain just as the unrestricted drawdown was beginning.

In the wake of the storm, combined tributary storage levels for the area above Chattanooga were about 104% of normal. They had been quite a bit below median levels before that event. These slightly higher reservoir elevations have allowed for some additional benefits, in terms of recreational use, hydrogeneration, etc.

All the precipitation has also helped increase groundwater levels, re-charging underground aquifers. This results in higher flows, in effect increasing reservoir elevations without additional rainfall.

Through concentrated efforts to recover storage levels, all of TVA’s tributary reservoirs are currently below flood guide levels, and almost all are well below that mark. According to the folks in charge of managing the river system, that means we are on a good pace to attain winter flood storage elevations—providing important flood-risk benefits at the time of year when they are most needed.

All main-river reservoirs are within their seasonal operating ranges, with the exception of Kentucky—which is about a half-foot above normal range because of special flows to support work being done on the Ohio River by the U.S. Army Corps of Engineers.

 

Current reservoir conditions
Reservoir
October 1, 2011
Observed Elevation1

October 1
Flood Guide2

January 1
Flood Guide2

South Holston

1717.8

1729.0

1708.0

Watauga

1951.5

1959.0

1952.0

Cherokee

1053.7

1069.0

1045.0

Douglas

975.0

991.5

954.0

Fontana

1679.8

1688.8

1653.0

Norris

1008.1

1020.0

1000.0

Chatuge

1920.8

1921.9

1918.0

Nottely

1768.1

1769.2

1762.0

Hiwassee

1504.9

1506.6

1485.0

Blue Ridge

1674.7

1678.8

1668.1

Tims Ford

887.1

888.0

876.1

Normandy

872.7

875.0

864.0

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

Well before the first raindrops fall, the work begins.

When the folks in TVA’s River Forecast Center first become aware that a storm event is likely to impact the Tennessee Valley, they follow a tried-and-true process designed to effectively manage the runoff that will inevitably end up in the reservoir system.

That process proved its worth yet again in early September, when the remnants of Tropical Storm Lee moved northeastward from the Gulf of Mexico. Tom Barnett, Senior Manager of River Forecast Operations, puts the situation in perspective: “People may think that the hardest part of what we do is to schedule the water that we’re receiving—to decide how long to hold it in certain locations, when to release it and how quickly, etc. And that can be a real challenge, no question. But the things we do in advance of the storm are just as important. One thing’s for sure: we don’t wait until we get wet to start working!”

He describes the chain of events that take place when he and his colleagues first become aware that a significant weather system is headed our way: “Because we are constantly monitoring the very latest forecasts, we see it coming—oftentimes up to a week or more before it actually arrives. We have an opportunity to minimize flooding impacts by getting out ahead of it, so work in the River Forecast Center tends to increase in intensity well before the rainfall does.

Busy Control Room

TVA personnel staff the River Forecast Center round-the-clock to manage inflows during storms. The most important work, however, is keeping pool levels where they need to be throughout the year—thereby providing adequate flood storage when it’s needed most.

Staff members stay busy gathering vast amounts of data as soon as it becomes available. They compare predictions from the National Weather Service with forecasts from other sources. “Just as important as how much rain we’re going to get is pinpointing where it is most likely to fall,” Barnett explains. “As soon as we begin to get an idea, we study the various scenarios and develop computer modeling runs. We do as much pre-flood work as we can, taking steps to mitigate the situation. For example, in this case—based on what was predicted—we drew the mainstem reservoirs down to the bottom of their operating ranges. The biggest difference we can make, however, is to aggressively maintain the reservoir system in what we call a ‘ready-state,’ which means that we’ve done what was necessary ahead of time in order to allow for the rapid implementation of operational changes. Constant readiness is the key piece of our strategy for being in the best possible position for flood risk reduction.”

All the while, the weather system moves ever nearer. But as even the most experienced meteorologists will admit, weather forecasting is not an exact science. Predictions are inevitably revised—sometimes significantly—as the anticipated path of the storm changes slightly or if it stalls out. Those working in the River Forecast Center must be ready night or day to quickly make adjustments based on a rapidly evolving forecast.

“It really helps that we have such a close working relationship with the folks at the National Weather Service in Morristown, Tennessee,” says Barnett. “We initiate contact with them well before the storm arrives and by the time it gets here, we’re all on the same page and operating with a high degree of confidence. The fact is, careful coordination between our agencies plays a big role in our ability to successfully deal with these types of events. In particular, we rely on their modeling to confirm our inflow forecasts for unregulated streams—those that don’t have a dam or other water control feature that can affect water levels. TVA, naturally, has no ability to control those waterbodies, but we still have to account for the flows that they add to our system.”

The collaboration works in both directions. The National Weather Service turns to TVA for river level forecasts that they use in their own computer modeling. Since they are responsible for most of the flood warning communications provided to the general public, their ability to depend upon TVA for timely and accurate forecasts has a direct impact on the quality of their flood-related forecasting—and consequently, on the safety of Valley citizens and the protection of their property.

By the time the wind picks up and the storm clouds begin to gather across the region, the situation becomes clearer and the actions more strategically focused. Armed with the very latest forecasts, Barnett and his co-workers develop and then implement an operating plan, based on what they have determined is the most likely probability for precipitation volumes and locations. But they don’t stop there, as he explains: “We also load the maximum rainfall estimate into our computer models, generating sort of a ‘worst case scenario’ that becomes the basis of our contingency plan. We always hope we don’t have to use it, of course, but we’re certainly glad we’ve got it—just in case.”

The deluge begins, and all the hard work pays off. The operating plan called for spilling water at all the mainstem reservoirs, with the exception of Fort Loudoun and Watts Bar. “Of course we always prefer to run water through the turbines, in order to maximize benefits,” says Barnett. “But sometimes the situation just doesn’t allow for it. With historic levels of precipitation, we didn’t have enough turbine capacity to use that water to generate electricity. As the runoff continued, we had to initiate spill operations in order to maintain levels below what we call ‘top of gates.’ It was unquestionably the right call.”

Spilling at Wilson

Water was released through the spillway gates at many TVA mainstem reservoirs during the heavy rains that fell across the central Valley in early September

In this case, the term “Labor Day” took on additional meaning. “In terms of staffing the River Forecast Center, it was all hands on deck during the holiday,” says Barnett. “The timing of this particular storm ruined a lot of picnics and days on the lake, but we were just extremely glad that the advance work we did had allowed us to get far enough out in front of it in order to lessen the impact. Most of the heaviest rains fell over the portion of the Tennessee River that lies between Knoxville, Tennessee and Guntersville, Alabama, so we were very justified in our decision to cut back to basically minimum flows at the tributary reservoirs during the event. That allowed for the additional storage space we needed on the mainstem reservoirs to reduce downstream flows as all the runoff entered the river system.”

The fact that the month of August was so dry across the Valley made a huge difference. The type of runoff that would normally be expected from a storm event of this magnitude didn’t materialize, in large part due to the dry conditions of the previous weeks. “As it turned out, we were slightly above flood stage only for a relatively short time and only at Florence, Alabama,” Barnett notes. “Careful management of the river system meant that very few impacts occurred as a result. Without the plans we’d put in place and certainly if August hadn’t been so dry, we would no doubt have exceeded flood stage at a number of locations along the Tennessee River.”

Spilling operations didn’t last long; within a week, water levels had receded and the mainstem reservoirs were back within range. In terms of the tributary reservoirs, all the “extra” water came in handy, Barnett explains: “Because we were entering the time of year for the unrestricted drawdown, the additional runoff we received gives us what we refer to as ‘discretionary’ water. It allows for some flexibility, in terms of when we use that water for generating electricity. By holding onto it for, let’s say, an unusually hot day when inexpensive hydropower can be used to great effect during periods of peak demand, we are able to help keep power costs lower—and that translates into benefits for ratepayers.”

Some people might say we dodged a bullet on this one. But Barnett doesn’t hesitate when it comes to ascribing what happened—or, more perhaps more accurately, what didn’t happen—to mere luck. “Yes, we were very fortunate to be dealing with this record rainfall on the heels of a dry period,” he says. “But there’s no question that the strategic decisions we made—before, during, and after the storm—resulted in protecting people and property from what would have otherwise been significant impacts. The process we follow during events of this nature is a sound one, and I’m happy to say that it has proved its worth yet again.”

 

Built to Last: Celebrating a Century of Hydropower at Ocoee #1

There are dams that are larger. There are dams with much greater capacities for storing floodwater. Or for producing hydroelectric power, for that matter. But at the age of 100 years, there’s not a single dam in the entire TVA system that’s older than Ocoee #1. And that’s something worth celebrating.

At TVA’s invitation, hundreds of folks recently came from far and near to Polk County in southeastern Tennessee to commemorate the occasion, gathering at Sugarloaf Mountain Park on the dam reservation. Saturday, September 24th was set aside as a family-friendly community day—a special event designed to observe and honor a century of hydropower production at the venerable Ocoee Dam #1.

Ocoee 100yr Cake

Those who turned out to celebrate the special occasion enjoyed food, music, power plant tours, and informational displays related to the hydroelectric project’s historic significance and current contributions to the TVA system. (Photo by David Luttrell).

The dam has actually been around longer than TVA itself. Built along the rugged Ocoee River and completed in 1911 by the East Tennessee Power Company, Ocoee #1 was one of the first hydropower projects in the Tennessee Valley. It was purchased (along with Ocoee #2) by TVA in 1939. Over the years, a couple of modernization projects helped preserve the dam’s structural integrity and bring it up-to-date. The dam was strengthened and resurfaced in the 1970s, and its turbines, generators, and control systems were upgraded in 1990. Thanks to these improvements and careful maintenance, the century-old hydroelectric project continues to contribute value to the TVA system.

TVA senior vice president of River Operations John McCormick recognized the impact of Ocoee #1 in remarks that were part of the day’s opening ceremony: “One hundred years after it went into operation, it is still producing clean, low-cost hydropower for the region. This dam changed the standard of living, the economy, and the recreational opportunities in this area as it shaped the Ocoee River.” 

No one understands that more than the people who work there. In her new role as Ocoee Plant Manager, TVA’s Annette Moore has a special appreciation for the dam’s significance—both in terms of its historic nature and the role it continues to play in providing benefits to Valley residents. “When I think about what it means to be in this position,” she says, “I am both humbled and honored. I am certainly conscious of what a great responsibility it is, on many different levels. We are committed to using the water that passes through this dam wisely, providing everything from low-cost hydroelectric power to recreational flows.”

Old PowerhouseCurrent Powerhouse

A view from inside the powerhouse at Ocoee #1, top, as it appeared many decades ago, and bottom, at present. Extensive modifications to equipment and controls have meant that the hydroplant is producing more electricity, in a more efficient fashion, that at any time during its 100-year history. (Bottom Photo by David Luttrell)

Moore cites a phrase used during the birthday celebration that she feels captures the essence of the project’s significance: “preserving the past to serve the future.” She says the remarkable record of success at Ocoee #1 is a testament to the employees—both past and present—who have worked there: “Thanks to their efforts, we plan to operate and maintain this hydro facility in such a way that it stays viable for many years to come. In terms of what it has meant and continues to mean to both TVA and the public, Ocoee #1 is truly a sustainable legacy.”


Fast Facts:
Ocoee #1 and Parksville Reservoir

The dam is 135 feet high and stretches 840 feet across the Ocoee River, which emerges from the Appalachian Mountains and enters the Tennessee Valley through a scenic gorge about 30 miles east of Chattanooga.

The impoundment forms Parksville Reservoir, which has 47 miles of shoreline and 1,930 acres of water surface.

Parksville fluctuates about nine feet from summer to winter and has a flood storage capacity of 19,000 acre-feet.

The hydroelectric plant at Ocoee #1 consists of five generating units, which are capable of producing approximately 24 megawatts of electricity at full generating capacity. That’s enough electricity to power about 14,000 typical homes.

A large model of a section of the river is located near Ocoee #1. It was built by TVA to guide the U.S. Forest Service in constructing the whitewater competition course for the 1996 Summer Olympics.


 

Update on Blue Ridge Dam Rehabilitation Project

The final phase of the rehab work is well underway. That’s good news for those who live along and enjoy recreation on the reservoir.

As outlined in detail in last month’s issue of TVA River Neighbors, the dam rehabilitation project is progressing according to schedule. The Blue Ridge reservation is a busy place right now, with the installation of two massive retaining walls consisting of 400 panels, each of which weighs between 1,000 and 4,000 pounds, tied into the earth behind them with long steel straps.

Downstream slope modification is the order of the day, with lots of crews operating heavy equipment to haul, dump, and place layers of sand, gravel, and rock on the embankment.

Plans call for the two-year project to be completed by summer of next year.

Dump Trucks

The downstream slope is being stabilized and strengthened as part of an effort to meet more rigorous safety standards. To date, crews have dumped more than 7,600 truckloads of material at the Blue Ridge worksite. A total of around 18,000 truckloads will be required to complete the project.

 

Improving public safety during water releases:
New Warning System at Watauga Dam, Modifications at 11 Others

Folks enjoying recreational activities in the waters below Watauga Dam will benefit from a newly-installed warning system which will employ signs, horns (during daylight hours), and strobe lights to alert them to discharges that will result in rapidly rising water levels.

By the end of October, changes will be made to existing warning systems at Appalachia, Blue Ridge, Cherokee, Douglas, Fort Patrick Henry, Great Falls, Norris, Ocoee #1, South Holston, Tims Ford, and Wilbur. During the day, horns and strobe lights will automatically activate prior to water level changes. At night, only the strobe lights will serve as warning to recreational users, in order to reduce noise impacts to local residences.

An additional modification is being made to the spillway warning system at Wilbur Dam. A warning system which had previously been operated remotely from TVA’s Power Control Center in Chattanooga will now be activated automatically when Wilbur’s unit four generator is turned on.

For more information on how to stay safe in the waters around TVA dams, locks, and powerhouses, go to 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.

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.