Basic Cumberland River Generation Schedule Information 04-25-21
Interpreting generation schedules is key to successfully fishing the Cumberland river.
Fishing the Cumberland river tailwater can be tough. Determining what type of water conditions might be encountered on a trip to the Cumberland can be difficult, especially for those new to the river system. First of all, fishing tailwaters such as the Cumberland is different than fishing mountain streams and free flowing rivers. Fishing tailwaters requires an intimate knowledge of release schedules, downriver water speed, effects of rising and lowering of water on fish, and lastly how to change tactics as conditions change. Knowing how to find release schedules and forecasts are not only key, but essential.
Fortunately, there are several tools available to Cumberland tailwater enthusiasts that allow planning for a successful trip to the river. There is a lot of information out there and how to interpret some of that information is the goal of this article. First, it’s helpful to know how a generation release schedule is determined for Wolf Creek Dam.
Each day, the COE runs a hydrologic model to determine the amount of water to be released from Wolf Creek Dam. The COE then provides TVA with a total generation amount that corresponds to the amount of water they want to release from the dam the following day. TVA then schedules the hourly releases for Wolf Creek Dam and publishes them to the web as the generation preschedule. Tomorrow’s generation preschedule is usually available in the early afternoon. If you follow the schedule over time you’ll notice that peak generation at Wolf Creek Dam often coincides with when you would expect peak power use, which is typically during the mid-morning and mid-afternoon.
So, the information in this sheet is not ddecipher and is terribly useful in planning a trip to the Cumberland. The information is broken down into 6-hour intervals for every 24-hour period and gives averages for every 6-hour interval. This combined with the TVA schedule will allow any angler to get a great read on what is occurring at the dam and the river. It’s important to note that TVA states release schedules are subject to change and large amount of water could be discharged at any time. Through the years I’ve only experienced a small handful of times where there has been deviation from scheduled generation. But, it does happen. In all, there is plenty of information for all anglers to use in preparing for a day on the Cumberland.
Once the release schedule is set, information about the schedule is published online in numerous places. Over the years, I’ve consistently used a couple of places to obtain information to assist me in making decisions about how I will tackle my guided trips. Two of these are discussed below.
The USACE Nashville District publishes a daily generation preschedule at: https://www.lrn-wc.usace.army.mil/preschedule.shtml
Note that this schedule is depicted in Central Standard Time. This schedule will give the current release schedule and a forecast preschedule for the upcoming 24 hours. This is extremely helpful as the schedule easily depicts how many units will be operating hourly in the column labeled ‘Wolf Creek'’. It’s important to note that one generator is typically depicted as “45”, 2 units is depicted as “90”, 3 units is depicted as “135, and so on. 1 operating generator equates to 2-3 feet rise in water within the river system. Each generator when in use can release approximately 3,500-4,500 cubic feet per second (CFS). Keep in mind that generators can become slightly more or less efficient during operation and a single generator may vary and operate anywhere between 35-55 Megawatts each. Unit discharge and energy output can be dynamic based on net head, and system energy demands. Currently the Corps is running generators at 50 MW each and getting about 3830 discharge per unit. The real time single generator output is not listed on the preschedule but knowing that it will be between 35-55 per unit, it’s usually easy to decipher. Units are also run for the full hour as listed in schedules. Rarely will a unit be run for a partial hour of generation. Another thing to keep in mind is the hours listed are considered hour ending. For example, if the preschedule shows 45 at hour 14 and 90 at hour 15 and 0 at hour 16, one unit will run from 1:00-2:00 pm, then two units from 2:00-3:00 pm, then no generation from 3:00-4:00 pm. For some reason most people are under the impression that Wolf Creek Dam has only 4 generators. The correct number is 6. Wolf Creek Dam can release not only water from generators, but also from sluice gates and spillways. The potential for just how much water could be released from Wolf Creek Dam is mind boggling.
The next place I look is https://www.lrn-wc.usace.army.mil/project84.shtml This is the Cumberland River Project Operations Reports.
Note this schedule is also depicted in Central Standard Time. It’s an updated version of the old Project 84 Reports. The information here is updated every 24 hours. The times listed on the far most left column are in Central Standard Time and begin at 1:00 am. The next column of data is “Mega Watts”. Wolf creek dam is capable of massive power generation through 6 turbines. This column currently lists 150 Mega Watts for 24 hours, a massive amount of energy.
The next column is the Elevation “Pool”. I watch this column in the winter and spring to see how quickly the lake is being lowered. Simply subtract the 24 Hr. Min from the 24 Hr. Max at the bottom of the column to get an idea of how the water level of Lake Cumberland is be lowered. Looking at the column of data from top to bottom give you an idea of what is happening in an hour by hour representation.
The next column is the “Tailwater” elevation. This data allows you to view an hourly representation of the elevation of the tailwater below the dam. If there is fluctuation in the generation schedule, there will be corresponding fluctuation in this column also.
The next Column is “Turbine”. This column allows an immediate view of exactly what the corps is releasing through the generator turbines. For the example posted, you can see that the turbine column is a consistent 11,490 over a 24-hour period. So 11,490/3830= 3.0 generators working.
The next column is “Spillway”. If this column is populated, there has been a significant and recent precipitation event that has caused the Corps to use the spillways on the dam to supplement lowering the lake. You can see from this example that there is more water coming over the dam from the spillways than from generators. However, there is no energy generated from the use of the spillways. The main benefit of the spillways is to disperse excess water from Lake Cumberland. Note that the spillway crest on the lake side is elevation 723. Spillway gates can only pass water if the lake elevation is above 723.0
The next column is “Sluice”. This column is typically populated with numbers in the Fall when the dissolved oxygen levels in the river become low. However, sluice gates can be used at any time. The Corps uses the sluices to increase dissolved oxygen in the river and lower water temperatures in the river. There are (6) sluice gates which are 6’x4’ and release about 1,500-1,600 CFS each. It’s immediately evident when sluices are in operation as they spray water from the bottom of the dam around 60’ into the air. Angler opinions on sluices vary greatly. Some anglers like them and some don’t.
The next column is “Orifice”. Sluice gates with restrictor plates are referred to as orifices. Two of the sluice gates had these restrictor plates installed on them about 15 years ago. So, there are 4 full sluice gates, and 2 orifice gates. There are no plans to add or remove restrictor plates as that is a large undertaking involving divers.
The next column is “Hatchery”. This column will always have 20 in it. Hatchery Creek receives 20 CFS (cubic feet per second) from the dam system 24 hours around the clock, 365 days a year. The only thing that will affect the level of hatchery Creek is heavy rainfall.
The next column is “Total”. This is simply the addition of the turbine, spillway, and Hatchery releases combined. So, 11,490 (Turbine) + 15,680 (Spillway) + 20 (Hatchery) = 27,190. So, you can look at the total column and get a good idea of how many generators worth of water is coming from the dam. In this example 27,190 / 4500 = 6. This means that the amount of water coming from the dam with this schedule is equal to 6 generators running. This equates to an amount of water that is at the top of the generation capability of Wolf Creek Dam.
The next column is “Inflow”. Inflow is a calculation of how much water is flowing into the lake. We know how much water is being released, and we know how much water is in storage based on the lake elevation. So, each hour, this is a calculation based on the hourly change in volume of water stored in lake Cumberland and the known discharge that hour. If the lake is rising, inflows will be higher than outflows. If the lake is falling, inflows will be lower than outflows.
So, the information in this sheet is not difficult to decipher and is terribly useful in planning a trip to the Cumberland. The information is broken down into 6-hour intervals for every 24-hour period and gives averages for every 6-hour interval. This combined with the TVA schedule will allow any angler to get a great read on what is occurring at the dam and the river. It’s important to note that TVA states release schedules are subject to change and large amount of water could be discharged at any time. Through the years I’ve only experienced a small handful of times where there has been deviation from scheduled generation. But, it does happen.
In all there is plenty of information for anglers to use in preparing for a day on the Cumberland.
There is a lot more information out there on river conditions, forecasts, DO, SEPA curve, etc, but that is for another post.
Thank you for reading this report. I hope it proves useful. I want to thank Robert Dillingham (P.E.) with the Army Corps of Engineers District Water Management Section for his assistance and sharing of hydrologic information.
Please feel free to reach out to me if you have any questions or want to talk trout.
Thank you and fish hard!