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Home / Susan Thrasher / Understanding the Caney Fork Generation Schedule

Understanding the Caney Fork Generation Schedule

February 25, 2016
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The Caney Fork River is one of the most popular trout fisheries we have in Middle Tennessee. The river below Center Hill Dam stretches for 26.6 miles before joining the Cumberland River near Carthage, Tennessee. There are a number of public access points along the river for boaters and fisherman to enjoy. However, with the river being a tail water, it is critical that the recreational user review the release schedule prior to entering the water to ensure a safe day on the river.

The generation schedule is often a topic of conversation with anglers, since we are all hoping and praying for the perfect fishing window. For most, this window means the turbines are shut down and no more that 250 cfs of water is flowing through the river.   However, due to the primary function of the dam, the water release schedule isn’t always conducive to our fishing schedules.

Center Hill Dam construction was completed in 1948 for the primary purpose of flood control and hydroelectric power generation. The dam is part of four storage or tributary projects within the Cumberland River basin operated by the Corps of Engineers (COE). These projects include: Wolf Creek, Dale Hollow, Center Hill, and J Percy Priest.  These projects are operated together to fulfill multiple operating objectives including: flood control, hydropower, recreation, water quality, water supply, and navigation. The watershed is modeled on a daily basis to allow the COE to meet these objectives. Using sophisticated, analytical tools and models, the COE is able to predict, over an 8-day period, the amount of water that will be released and the power it will produce. This information, coupled with Tennessee Valley Authority (TVA) and Southeastern Power Administration (SEPA) power demands, help to establish the generation schedule.

TVA provides a generation release schedule, which is updated periodically throughout the day. The next day release schedules are typically available by 6 p.m. of the current day. The schedule for Center Hill may be viewed at the link below.

 

https://www.tva.com/Environment/Lake-Levels/Center-Hill

A free and convenient TVA Lake Info App is also available for your iPad and iPhone on the App Store.

The chart below is a typical screen shot from the TVA site. For this particular day, the schedule indicates that water will be released from noon until 4 pm. The water takes some time to reach the various access points after the horn sounds and the water is released. The first public access point with a boat ramp below the dam is known as “Happy Hollow.” Under one generator, the water level will typically begin to rise approximately 1.5 hours after the water is released. In this example, if you are in the water at Happy Hollow, you should make your way to shore no later than 1:30. The water will reach the next public ramp access, known as Betty’s Island, approximately 2.5 hours after the water is released.

Generation Releases

Until further notice, generation will be supplemented by sluice gate releases

Day Time Period (Central) Generators
10/02/2014 noon – 4pm 1
10/02/2014 4pm – midnight 0

 

If you do not have on-line access, you can also access the TVA information by calling 1-800-238-2264 then option 4 for water release schedules and option 37 for Center Hill Dam.

It is important to keep in mind that this is only a prediction, and generation schedules are subject to change. It is also important to pay attention to any special messages on this generation release forecast. In the example above, notice the bold text cautioning that generation will be supplemented by sluice gate releases. This means that from noon to 4pm one generator will be on and a sluice gate will also be open to supplement the turbine generation with cool, oxygenated water. Sluice gates are discussed further below.

Center Hill Dam has 3 main turbines and 1 small turbine to operate the facility itself. Approximately 3500 cfs flows through each of the main turbines, giving a high flow of 10,500 when all 3 generators are running. Higher output is possible; however, it is less efficient, so we seldom see turbine flows higher than 10,500 cfs.

During the initial construction of the dam, sluice gates were used to help pass river flow while the dam was being built. Today, the gates are used to help improve water quality by adding cold and oxygenated water to the river. There are 6 sluice gates located near the base of the dam. The gates are 4 feet by 6 feet and, when open, each gate allows a flow of about 1500 cfs. One of the gates has been modified with the addition of an orifice gate, which allows a small continuous release of 200 to 250 cfs. This orifice gate is often used after the turbines are shut down, during very dry conditions, to maintain a steady flow in the river. Center Hill Dam also has eight spillway gates. This provides another outlet for releasing water from the lake; however, the spillway crest elevation is 648 so water cannot be released from the spillway gates unless the lake is higher than elevation 648.

The sluice gates must be manually operated at the dam, however the turbines are operated remotely from Cordell Hull Dam. When a sluice gate is in operation, a high fountain of water, caused by the pressure of the water rising to the surface, can be seen at the base of the dam. The turbulence associated with the release, aerates the water, increasing the oxygen levels.   This serves to offset the low oxygenated water released from the depths of lake coming in through the turbine.

In the summer, the weekend release schedule typically offers a better fishing window since the power demand isn’t as great as during the week. A release (or pulse) in the morning allows cold water to flow through the river during the heat of the day.   The COE closely monitors the temperature levels and dissolved oxygen in the river to protect aquatic habitat and maintain the fishery.

During the fall, the COE draws down the lake, reducing the water held in the reservoir. This is to make room for runoff resulting from rainfall events during flood season (winter and spring). Operations at Center Hill are coordinated with those at the other storage projects to provide flood control capability for the reservoir system. This is done gradually through the fall so water is conserved for generating power. Then, in February, the COE begins storing water so that a full pool can be reached by May. This will be the storage bank of cool, oxygenated water that will be released through the summer and fall and maintains the quality of the water.

Over the past few years, the Corps has been operating under IRRM pool level restriction, an Interim Risk Reduction Measure. The lake level has been kept at a much lower level to reduce risks related to the seepage issues at the dam. This means that significant water is released throughout the winter and into the summer. The Corps must draw down water aggressively to keep the lake level at 630 feet. In comparison, during normal times, summer pool is held at 648 feet. With continued dam construction improvements underway, it is currently unknown when this restriction will be lifted.

However, all is not lost. It’s been a long and wet winter making it difficult to maintain the lake below the elevation 630 target, but occasional fishing windows should be here before we know it. When the lake falls to 633, the COE will begin slowing their releases from the lake, and when it falls below 630, releases will be slowed down even further.

The chart below illustrates observed data from the TVA site:

Observed Data

Day Time (Eastern) Reservoir Elevation (behind dam)* Tailwater Elevation (below dam)* Average Hourly Discharge*
2/25/2016 5 am 634.00 489.60 14,300
2/25/2016 6 am 634.04 489.74 14,300
2/25/2016 7 am 634.08 489.68 14,300
2/25/2016 8 am 634.12 489.72 14,300
2/25/2016 9 am 634.16 489.76 14,450
2/25/2016 10 am 634.19 489.69 14,300
2/25/2016 11 am 634.23 489.73 14,600
2/25/2016 12 pm 634.26 489.66 14,30

Although providing the fishing windows throughout the year would make many of us anglers happy, the reality is that there are many other operating objectives in addition to recreation that the project is designed to support.

So, keep an eye out for those fishing windows, get outside and enjoy it when it comes!

Special thanks to Mr. Bob Sneed and Robert Dillingham, US Army Corps of Engineers, Nashville District, for their time and valuable input, making this article possible.

 

 

 

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About Susan

Susan Thrasher

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My Bio

Susan Thrasher, an FFF certified instructor, is the owner and operator of Southern Brookies Fly Fishing in Lancaster, Tennessee. For over a decade her teaching passion has extended into leading Casting for Recovery in Middle Tennessee and as a staff instructor at the Joan Wulff School of Fly Fishing in the New York Catskills.  In 2007, Susan and Nikki Mitchell founded the Music City Fly Girls, a Nashville based women's fly fishing club with over 40 active members.