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 FLIPPIN
- The late summer and early fall threat of low oxygen levels in Arkansas
trout waters is still hanging around, but there are possible solutions,
Darrel Bowman, Arkansas Game and Fish Commission trout biologist, said.
Bowman told the agency’s commissioners at their June meeting in Flippin
about new technologies that could be used to increase dissolved oxygen
levels in Arkansas' trout fisheries.
At present, there are periods when the dissolved oxygen levels in water
released from Bull Shoals and Norfork dams are below the Arkansas
Department of Environmental Quality's minimum requirements for a
coldwater fishery.
The ADEQ requires 6 parts per million (ppm) of dissolved oxygen for a
coldwater fishery. During the summer, conditions in water released from
the two northcentral Arkansas dams reach 4 ppm during generation and
below 1 ppm at base flows. Eight ppm is required for normal spawning
success in trout and 6 ppm is required for healthy fingerlings and adult
trout. At 3 ppm of dissolved oxygen, trout may begin to die.
The long-sought
remedy to the problem is a minimum flow of water through the dams, and
AGFC officials have sought this for a quarter-century.
Forrest Wood of Flippin, who is ending his seven-year term as an AGFC
commissioner on June 30, said, “My only real regret about these seven
years I have served has been that we still don’t have minimum flow for
these trout streams. It’s frustrating. We’re so close (to a solution),
but we still don’t have it.”
Through years of negotiations, the federal Southwest Power
Administration, which controls the power operations, has declined to
allow water from the “power pools” of Bull Shoals and Norfork lakes to
be committed to a minimum flow agreement. The Corps of Engineers
operates the dams and in recent years has agreed to the minimum flow
concept if Southwest Power approves.
In late summer and early fall, water levels are low, especially in times
of drought. These are also times of lowered generation at the
power-producing plants of Bull Shoals Dam and Norfork Dam. When oxygen
is extremely low, the trout are in danger of dying. When the oxygen is
somewhat low, the spawning, mostly for brown trout, is disrupted.
The answer is to release a small amount of water from the dams in the
low oxygen periods, biologists say. But the obstacle is there is no
provision in the congressional authorization for the dams for fish or
for recreation. Both dams were built for the specific purposes of flood
control and electricity generation.
A temporary fix for the problem, a “Band-Aid” approach, Bowman said,
could be put in place quickly and with little cost. He said, “The Corps
says it is studying this.”
Just by using a large powered aerator in each river below the dams,
enough oxygen could be put into the river to keep trout alive during
critical periods, according to Bowman. Cost? $7,000 for each of two
aerators.
The aerators are similar to those used at the AGFC’s fish hatcheries and
at commercial fish farms in several parts of Arkansas.
Bowman gave the commissioners a summary of long-range but costly
strategies to putting more oxygen into the water below the dams. The
proposals had input from the Tennessee Valley Authority, Bowman said,
which has many years’ experience with power-producing dams in the
Tennessee River system in Tennessee, Alabama and Kentucky.
Autoventing turbines could solve the problem, and these could come into
place as the existing turbines wear out, Bowman said. This system would
put much more oxygen into the water, but the cost would be high -- about
$10 million for installation of the new turbines.
“Forebay oxygen injection” may be the best long-range plan, Bowman told
the commissioners. This would be a system of pumping oxygen through an
underwater “soaker hose” in front of the dams. Cost would be about $2
million for installation and $2 million a year for operation. |
