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By Duncan Mansfield
Associated Press
Knoxville
– Once desolate riverbeds below Tennessee Valley Authority dams in
Tennessee, North Carolina and Georgia are now brimming with wildlife thanks
to the federal agency’s pioneering efforts to keep oxygen-rich water
flowing.
“The change is nothing short of dramatic,” said Jim Habera, a
fisheries biologist with the Tennessee Wildlife Resources Agency.
The improvements have been seen on a host of Tennessee River
tributaries – the Clinch, Holston, Hiwassee, Elk and Duck rivers, among
others. TVA studies on some of these rivers are finding that fish and key
insect populations have doubled.
“It went from a river that really was not a really good trout
fishery to one that a lot of people say is one of the best east of the
Mississippi,” Steve Brown, president of the State Council of Trout
Unlimited, said of the Clinch, west of Knoxville.
And it’s not just that the fish are jumpin’, he said. The whole
ecosystem has improved with the water quality.
“It went from being a very rare thing to see a great blue heron
to frequently seeing two or three. And there are others, mink, weasels and,
of course, deer and wild turkey. It is a great place for critters,” Brown
said.
TVA, which provides electricity for 8.5 million people in seven
Southeastern states, began damming the Tennessee River and its tributaries
in the 1940s.
It wasn’t until 1991 that the agency made a serious effort to
restore the tailwaters below the dams. For the first time, it adopted a
policy of minimum water flows through the dams and developing ways to add
life-sustaining oxygen in the summer.
Since then, TVA estimates it has increased dissolved oxygen
concentrations in more than 300 miles of rivers downstream of its dams and
improved water flow in 180 miles of river.
The agency spent $44 million in the early 1990s beginning to
make these improvements at 16 dams throughout the Tennessee River’s 652-mile
watershed. It is now in the final stages of a $17 million second round, to
be completed in 2006.
The latest enhancements are aimed at offsetting a revised
reservoir operations plan that delays the seasonal drawdown of the lakes
until late summer to benefit recreational users and lake residents.
“The original equipment that was put in was not sufficient to
handle the additional load,” said Chuck Bach, TVA plant manager.
TVA has used a variety of techniques to boost oxygen.
It has redesigned hydro-electric turbine blades to add oxygen as
water passes through. It has installed fanlike pumps to drive oxygen-rich
water from the surface down to the oxygen-depleted water at the bottom of
the dam. And it put in waterfall-like weirs that add oxygen as the water
cascades over them.
TVA’s new major push is installing oxygen-injection systems that
send pure oxygen to the bottom of the lake through a network of plastic
pipes and let it bubble up through defuser lines – a kind of lawn sprinkler
system in reverse.
Nine dams have gotten these new systems – Watts Barr, Fort
Loudoun, Cherokee, Douglas, Norris, Nottely, Hiwassee, Blue Ridge and Tims
Ford. Three more may get them in 2006 – Watauga, Boone and Chickamauga.
TVA controls the whole thing from the agency’s river management
operations office at TVA headquarters in Knoxville, where any valve can be
opened with a computer keystroke.
“We are setting the bar for others. People are coming to us,”
said Bach, noting TVA has provided consulting services on these systems to
the Army Crops of Engineers and to other agencies domestically and abroad.
The program has proved popular both outside and inside TVA, he
said, and the agency is committed to further improvements as new technology
comes along.
FACTS ABOUT RESERVOIR RELEASE PROGRAM
A
look at the Tennessee Valley Authority’s efforts to improve the tailwaters
below dams in Tennessee, North Carolina and Georgia:
n
Dissolved
oxygen concentrations are up along more than 300 miles of river
n
Water flow
is greater on 180 miles of river.
n
Studies
suggest increases in key insect and native fish populations (trout) and
successful reintroduction of species (mussels, sturgeon).
n
Thirty-six
miles of aeration lines have been laid to pump pure oxygen from lake
bottoms.
n
Aeration dams:
Watts Bar, Fort Loudoun, Cherokee, Douglas, Norris, Nottely, Hiwassee, Blue
Ridge, Tims Ford, Watauga, Boone and Chickamauga.
n
Others
monitored:
Apalachia, Chatuge, Fontana, Fort Patrick Henry and South Holston.
n
Cost:
$61 million since 1991.
n
Source:
Tennessee Valley Authority |