Cumberland River Fly Fishing Report 10-13-18
3 generators (2) sluice gates and (1) orifice at Wolf Creek Dam
What's going on with the generation at Wolf Creek Dam? I've been asked that question more over the past two weeks than I have over the past 17 years. It's prime time for fishing on the Cumberland river, but recent generation schedules are keeping most fly fisherman off the river. Central and Southeastern Kentucky usually average 2-3 inches of rain for the month of September, but an unusual weather event dumped 8-11 inches of rain on top of the Cumberland river drainage system over a six day period during the middle of September. The result of this precipitation was that the surface elevation of Lake Cumberland rose close to ten feet. TVA / COE generation schedules have been running ever since in an effort to lower the lake to a determined level. A combination of 2 generators and 2 sluice gates averaging 2160 total megawatts over a 24 hour period have been the consistent generation schedule for several weeks now . From time to time there has even been the use of a restrictor plate. The only break in the generation was a few days ago when all generation was shut down for 11 hours to search for a boater/swimmer that had disappeared in Lake Cumberland. Anglers with motorized boats can motor up and float back down the river and catch a fish here and there, but drift boats which are the workhorses and fish catching machines of the river have been held at bay due to high water. So, how do we know when the river will be back to normal fishing conditions? What does this mean for fall fishing and how will water quality be effected? I'll explain in detail below how all of this is determined and played out.
It turns out that there are many factors that go into COE / TVA generation schedules other than just trying to reduce the water level of an impounded lake after a large rain. A very large part of the fall fishing equation is measurable amounts of dissolved oxygen at a certain stratified level within the lake. A certain level of dissolved oxygen is needed in order for fish health to be optimal within the river. You may notice during late summer months on the river that trout still fight immediately after the hookset, but seem to tire more quickly than normal. In contrast, when sluice gates begin operation, it's easy to see the energy level of trout rebound in an unbelievable fashion. As an example,14-16" fish suddenly tug like they are 20" ers with the added benefit of increased dissolved oxygen levels. It's comparable to us running a mile at sea level where plenty of oxygen is present and running a mile at 14,000 feet above sea level where oxygen levels are depleted. The lack of oxygen effects everything, especially production of ATP which is the fuel in biological cellular processes.
During this time of year the dissolved oxygen content of large bodies of water like Lake Cumberland becomes less and less the further the distance traveled below the surface of the water. Roughly at the same level that dissolved oxygen content in the lake begins to diminish is around the same area that the intakes for Wolf Creek Dam are located. If you're really interested, you can go online and read all about thermal stratification of the hypolimnion, epilimnion, and metalimnion. So, what occurs is that when generators are in use, the generators push water through the turbines that has a low dissolved oxygen content when it enters the river at the dam. This has a negative effect on general fish health. The COE / TVA and KDFWR all work together to determine when and how to approach the issue of low dissolved oxygenated water coming from the dam when dissolved oxygen levels fall below certain values. It should be noted that 3 units (generators 1, 3, and 5) at Wolf Creek Dam have air supply lines installed which assist with increasing dissolved oxygen content. There are also hub baffles installed on some of the generators which are basically fingers or metal bumps installed on generator turbine blades which act as influence to create dissolved oxygen when turbines are running. However, these measures are often not enough to create desired and acceptable levels of dissolved oxygen. It's at that point that sluicing becomes an important option. As with all options there are pro's and a con's. In this instance the pro is that the sluice gate provides and delivers extremely valuable dissolved oxygen content to the river which in turn assists promoting optimal fish health. The con is two fold in that (1) it increases the amount of water coming down the river and (2), it prohibits major generation. I know that may sound confusing, but I'll try and explain. In our current position on the Cumberland river as stated earlier, there have been 2 generators and a 2 sluice gates running continually for several weeks and that's all great. However, in order to reap the benefit of dissolved oxygen that a sluice provides there really can't be more than 2-3 generators running. More than 2-3 generators in operation negates the amount of dissolved oxygen that the sluice gates provide. In other words, the mixture of non dissolved oxygenated water and oxygenated water is not optimal. So, the main point is that it takes a very long time to lower lake levels with fewer operating generators in order that dissolved oxygen levels can remain high for fish health.
Catch and Release
Now, the good news. At a certain time of the year in late fall, usually sometime in November, Lake Cumberland will turn over or flip. Using a limnological term, the lakes thermocline will reverse itself. When this occurs the higher dissolved oxygen content located closer to the top of the lake will now be located lower in the lake and the lower dissolved oxygen content of the lake will be near the top. When this happens the COE / TVA will stop sluicing. There will no longer be a reason to hold generation to only 2 generators. At that time the COE / TVA could potentially use 6 generators for 8 to 10 hours of the day and have periods of no generation which would be great for anglers trying to fish for trout. With the onslaught of shorter days and cooler daytime temperatures that lake 'flip' will occur faster. Exactly when will it occur, only mother nature knows.
So, what can we expect for the near term future? I can inform you that the goal of the COE / TVA is to obtain a lake level of 710' by October 19th. That means that the current generation schedule will be in effect for at least another week. Please keep in mind that this goal is strongly dependent on upcoming precipitation events. The next goal is for lake levels to be around 708 by the end of October. So, with this information, we should be able to track the lake levels in published project 84 reports and flowsheets to see trends as to when generation schedules will slow and meet favorable levels.
With the Cumberland river out of whack, many anglers will turn to Hatchery Creek to get their fly fishing fix. Enjoy this silly little video I made a while back of a short morning on the creek. Please excuse the poor editing!
Hatchery Creek Video
I know that there is a lot of information in this report. I've tried to keep it simple. There is so much more information out there about how and why tailwaters like the Cumberland River operate as they do. In my next report I'll try and tackle how you can read published flowsheets for the Cumberland River to analyze trends in generation and how you can use this information to plan your trip to the river days in advance.
Thanks to each of you that have e-mailed, called, or texted about fishing and conditions on the river. It's been nice to hear from you all. My apologies again to those of you that I've had to cancel on, but I don't believe in guiding unless it allows opportunity for anglers to be successful.
Thanks also to all of you that follow Cumberland Bottom Ticklers on social media. As usual, if you want to get out and experience the best tailwater in the East, call, text, or e-mail me at any time.
Keep checking the CBT website, Facebook and Instagram pages. I'll post as soon as conditions make a change for the better.
Thanks and fish hard!