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May 10, 2011

In this issue:

Rain and runoff
Reservoir elevations
Reservoir operations
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

Since January, rain in the Tennessee River Basin has been about 109% of normal—and runoff (precipitation that flows over the ground and is not absorbed into the soil) has been around 107% of normal. So much rain fell in March and April that it quickly made up for a dry January and February.

The wet weather associated with storm events in late April capped off a rainy couple of months, resulting in some impressive totals for both rain and runoff. The most noteworthy accumulations were for the lower end of the river system, where numerous storms rolled through in rapid succession. For the western part of the Valley, rain was 198% of what it typically is during the month of April and runoff totaled a whopping 225% of normal.  

 

Reservoir Elevations

The abundant rain/runoff during March and April could hardly have occurred at a more opportune time, in terms of the spring fill.

All the main-river reservoirs are at or very near their seasonal operating ranges, with one exception: Kentucky is significantly above, due to flood control operations on the Ohio River.

Almost all of the tributary reservoirs are at or slightly above targeted seasonal elevations, due in no small part to the recent heavy rains. Hiwassee Reservoir is still slightly below, but is expected to reach full pool very soon.

Bottom line? TVA managers have seldom been as confident about reaching June 1 target levels at each of the tributary reservoirs—with the exception of Blue Ridge, where work on a dam rehabilitation project has impacted elevations.

It’s a relatively unusual position to be in at this time of year. Typically, TVA is releasing only enough water to meet downstream minimum flow requirements—in order to reach target levels for recreation by June 1. With so much extra water with which to work, it’s been possible to use some of it to generate additional electricity—over and above what would usually be feasible during the weeks immediately preceding the June 1 target date for reaching full pool.

Every year during the spring spawning season, TVA attempts to keep reservoir levels steady to benefit the fishery—and this year is no exception. It becomes a more challenging proposition during flood control operations, but care has been taken to maintain—to the extent possible—stable to slightly rising elevations.

 

Current reservoir conditions

Tributary Reservoir Elevations¹
Reservoir

May 9, 2011
Observed Elevation

May 9
Flood Guide2

June 1
Flood Guide2

South Holston

1729
1729

1729

Watauga

1959.4
1959

1959

Cherokee

1067.3
1066.6

1070.9

Douglas

992.2
990.6

994

Fontana

1699.9
1698.1

1703

Norris

1021.8
1020

1020

Chatuge

1924.5
1924.3

1926

Nottely

1776
1774.6

1777

Hiwassee

1515.6
1517.1

1521

Blue Ridge

1668
1684.9

1687

Tims Ford

889.7
887.1

888

Normandy

784.9
875

875

1 Elevations above mean sea level
2
Flood 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

All-time record high water levels at Kentucky Reservoir… The Army Corps of Engineers blowing up a levee at the confluence of the Ohio and the Mississippi Rivers to reduce flooding upstream… Workers at TVA’s Shawnee Fossil Plant placing sandbags around critical equipment and preparing for the possibility of shutting down units, if those measures didn’t work…

KentuckyDam
In coordination with the Army Corps of Engineers, TVA moves water through Kentucky Dam in early May, in an attempt to stay ahead of the flood crest. The spill rate is in excess of approximately 130,000 cubic feet per second, with a tailwater elevation of 339 feet. (For context, a normal tailwater elevation is around 302 feet.)

“Unprecedented.” That’s the word David Bowling uses to describe some of what occurred as a result of the after-effects of the devastating storms that moved through the Tennessee Valley on April 27. As Senior Manager of TVA’s River Forecast Center, Bowling has seen a lot over the past 15 years of working to route water through the river system, but he says that much of what occurred in the wake of the storms was uncharted territory.

“We were handling ‘coordination calls’ with state and Federal agencies before, during, and after the event,” Bowling explains.
“By staying in close contact, we are able to provide accurate and timely information about conditions that we feel are likely to occur in order to allow for a more effective response.”

Immediately after the tornadoes passed through, most people focused—quite understandably—on the tragic loss of life and property throughout the region. So it may be surprising to note that some of the most serious impacts from the storms don’t really make themselves fully felt until long after the rains stop and the damaging winds die down.

Even an entire week later, the challenge of managing the increased flows resulting from all that rainfall and runoff was still considerable. But what many people may not realize is that a lot of critically important work was done well in advance of the actual storm events. “By closely watching the long-range forecasts, we get a ‘heads up’ and actually start making an effort to manage the situation long before it starts raining,” says Bowling. “For example, we ran a significant amount of water during the whole month of April—and were in spill operations throughout the system at least two weeks prior to the advent of the late April storms. As we watch these kinds of weather systems develop, we’re pulling the main river reservoirs down—holding a lot of water back in the tributary reservoirs of East Tennessee and North Georgia, away from the lower part of the river system, in order to support flood control operations on the Ohio and Mississippi Rivers.”

Because of the destructive nature of these particular storms, the benefits of hydrogeneration as a power source were once again starkly illustrated. When transmission lines from Browns Ferry Nuclear Plant were brought down by the damaging winds—rendering that facility temporarily incapable of providing electricity—generating capacity from Guntersville, Wheeler, and Wilson Dams quickly helped to make up the difference.

TVA Senior Vice President of River Operations John McCormick provides helpful insight on the role of hydropower in these kinds of situations: “Although hydrogeneration accounts for only about 10% of TVA’s generation capacity, its quick response and flexibility makes it invaluable in responding to a crisis like we observed in late April. While most generation sources take hours or even days to come on and then produce a constant amount of power, hydro can bring on hundreds of megawatts in a matter of minutes and then regulate up and down as demand shifts."

Several days later, Bowling and his colleagues in the River Forecast Center found themselves effectively ceding control of directing releases from Kentucky Dam to the Army Corps of Engineers. When waters reach the 35-foot stage at Cairo, Illinois, that triggers a mechanism for the Corps to assume that aspect of operations; they sort of “take over” at Kentucky, with the goal of coordinating a regional effort to minimize flooding on the Ohio and Mississippi Rivers.

Unfortunately, so much rain had fallen within the Ohio and Mississippi systems that even cutting Kentucky back to absolute minimum flows ultimately had little impact on downstream flooding.

Bowling is quick to point out, however, that the operations at Kentucky were instrumental with regard to one very important aspect of flood response. “They say that timing is everything—and in this case, that proved to be true,” he observes. “We worked closely with the Corps to provide input on how high to take water levels. When calls came in from various emergency management agencies to say they were still in the process of putting measures in place to try to handle these flows, we were able to buy them some additional time. In this case, there was so much water coming down the Ohio River that Kentucky Reservoir’s storage could not eliminate flooding, but we were able hold off the inevitable for a critical period of time. And sometimes, that makes a great deal of difference to a great many people.”

 


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 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.

 
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