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HL 2016 09 27

The document discusses potential vortex issues at various Bureau of Reclamation projects, including Black Canyon Dam, Caballo Reservoir, and Davis Dam. Observations indicate that vortex formation can occur under specific water surface elevation conditions, which may affect operational stability and maintenance activities. Future studies are suggested to estimate critical water surface elevations for vortex formation and to explore mitigation strategies.

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14 views1 page

HL 2016 09 27

The document discusses potential vortex issues at various Bureau of Reclamation projects, including Black Canyon Dam, Caballo Reservoir, and Davis Dam. Observations indicate that vortex formation can occur under specific water surface elevation conditions, which may affect operational stability and maintenance activities. Future studies are suggested to estimate critical water surface elevations for vortex formation and to explore mitigation strategies.

Uploaded by

neerajkumar.rs.mec23
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Interviews with Selected Bureau of

Reclamation Projects
Note: At any of these projects, there is potential for future vortex issues should
the water surface elevation drop due to drought, maintenance or any other
circumstance. A study would be required to estimate a water surface elevation at
which a potential vortex could form.

Black Canyon Dam

A type 2 to type 3 vortex has been observed at Black Canyon Dam when the WSE
is drawn down about 15-18 feet from the normal pool elevation. The submergence
to the top of the horizontal intake is about 4 feet at the lower WSE where vortex
formation has been observed. This elevation does occur with some regularity as
the reservoir is drawn down for maintenance on the drum gates. There is currently
an operational restriction to shut down the two turbine units if the WSE is 2 feet
below the top of the intake gates. It has been observed that there is some
instability in the power output when a vortex is present. During irrigation periods,
the WSE is considerably higher and has around 21 feet of submergence to the top
of the intake gates. During this fall, the reservoir will be drawn down to allow
construction of an additional penstock and turbine unit at the Dam. The elevation
of the new intake will be lower, which will reduce the likelihood of vortex
formation. There have not been any attempts to reduce vortex formation with a
vortex suppression device.

Caballo Reservoir

Caballo reservoir is currently being drawn down in an attempt to remove trash


and obstructions from the trash rack at the outlet works. When the reservoir WSE
was near the top of the trash rack (about 35’ above the invert), vortices were
observed. Operation staff have been using compressed air and have been able to
remove some debris from the rack, but a large amount is still wedged between the
bars. Since only the top of the trash rack is visible, there is no current estimate of
the amount of obstruction, but structural members are observed to be bent due to
the forces. A fire in the watershed in 2014 is likely responsible from some of the
debris in addition to a vegetation management plan that raised WSE and therefore
mobilized some debris. As the WSE is dropped for irrigation demands, that debris
is likely being pulled towards and into the trash rack.

Davis Dam

From the description of the operators, a type 3 vortex has been observed
occasionally at Davis Dam. They are typically located near the piers between the
intakes, and can be as large as a pie plate on the surface with a depression that
goes down potentially 20 feet. When a vortex is present, no impacts to the

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