Here is what I know... written in 2001. I can't attest to continued accuracy.
JUST ADD OXYGEN
By Richard Simms
Hawaiian singer Don Ho sings a tune called Tiny Bubbles. “Tiny bubbles in the wine, make me happy, make me feel fine...”
The fish in the Tennessee River would like that song. They could do without the wine, but they desperately need those tiny bubbles.
The fish and other aquatic organisms don’t ask for a lot. Just about six molecules of oxygen for every million molecules of water (actually 6 mg/L) and they’ll be happy. Give them less than that however, and they get stressed, or even die.
That’s exactly what was happening in some TVA lakes and rivers. During summers with little rain and low flow, coupled with the dams that slow the flow even more dramatically, many TVA lakes and tailwaters became dangerously low on dissolved oxygen.
“It used to be that in some places, the oxygen was completely gone,” said Rick Bivens, a Stream Fisheries Biologist for the Tennessee Wildlife Resources Agency. “We’d even had fish kills as a result.”
Ten years ago, at the urging of the public, TVA officials made the commitment to do something about the problem. Between 1991 and 1996 they spent $50 million on the Reservoir Releases Improvement Program. The money went toward a variety aeration equipment like auto-venting turbines, line diffusers, aerating weirs, air compressors, and surface water pumps at 15 different dams. Basically large scale projects that do the same thing as the tiny aerator in your aquarium.
“The furthest downstream that we did work is Watts Bar Dam,” said Wayne Poppe, TVA Senior Manager in River Operations. “The focus was on the real deep, tributary reservoirs.”
That’s because the problem is magnified in those reservoirs, mostly in Upper East Tennessee. During the summer the deep lakes actually stratify into layers with the lower layers becoming almost completely depleted of oxygen.
And that deepest water by the dam is where you’ll usually find the intakes for the hydroelectric turbines, which send that oxygen-depleted water pouring downstream toward the rest of us. Remember... we all live downstream. The end result was problems for the aquatic life in many rivers.
Poppe says no two rivers or dams are the same. Each one has different characteristics that call for different means to increase the oxygen levels. At Watts Bar they use liquid oxygen injection. There are hoses, just like a garden irrigation hose, running out into the lake above the dam. Sensors detect when the dissolved oxygen is too low and inject oxygen into the water.
“Last year we used a little over 3,000 tons of liquid oxygen at Watts Bar,” said Poppe. “For the entire reservoir release activity we spend a little over $3 million a year in operation & maintenance.”
Poppe says at Chickamauga Dam TVA has an agreement with the state of Tennessee to guarantee a minimum flow rate, primarily to guarantee enough water so the Moccasin Bend Treatment Plant works correctly. The guaranteed flow rate is high enough to maintain the target oxygen rate of 6 mg/L without additional artificial help.
The most visible benefits of the program are upstream north of Knoxville at places like the Clinch River below Norris Dam and the South Holston River below Cherokee Dam. TVA outfitted both dams with weirs or other means of increasing the dissolved oxygen.
Bivens says, as a result of the improved water quality, TWRA started trout stocking programs that have been unexpectedly successful. “We've been kind of surprised that fish seem to be able to make it year-round,” he said. “We intended for it to be just a put-and-take fishery. But trout have been able to hang on year-round.”
“The fishing has definitely improved quite a bit,” says Ryan Meulemans at Chattanooga’s Choo Choo Fly & Tackle. When Meulemans isn’t working, he’s trout fishing. “I’d say that right now the South Holston is one of the few rivers in the state of Tennessee, that if you make the trip up there, you stand a good chance of catching an 18-inch trout.”
“It was probably five or six years ago when I made my first trip to South Holston,” he said. “I heard TVA seemed to manage that river well and that due to good water levels and water quality the (insect) hatches were consistent and pretty heavy. My first trip was on a New Year’s Day and cold. But the fishing was great. I actually had great dry fly fishing."
Meulemans says 14 or 15-inch trout are the norm. And again, with year-round populations and growing conditions, he says 18-inch brown trout aren’t unusual.
Poppe says the Reservoir Releases Improvement Program has improved water quality in 300 miles of river, and has been recognized and awarded by a variety of national organizations including the Wildlife Habitat Council and the National Hydropower Association.
Meulemans had no idea TVA spends $3 million a year on the program. "That surprises me a little bit," he said. “In my experience with the Hiwassee, TVA hasn't been real great with managing that fishery... but it's great that they're spending that much money on other rivers."
Lot’s of recipes say, “just add water.” In this case there’s plenty of water. TVA says “just add oxygen.”
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