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Roza Proposed Operating Conditions

by Jim Higgs, Warren Frizell, and Scott Klein.

This is an on going project. As such, information presented here is primarily for communications with clients, it is a work in progress, and it is not complete or peer reviewed.

Roza Diversion Dam located 10 miles north of Yakima, in south-central Washington, and diverts water from the Yakima River. The dam is a concrete weir, movable crest structure, 486 feet long at the crest, 67 feet high, and contains 21,700 cubic yards of concrete.

The key reason Warren Frizell and I are involved with this project is for the downstream passage of juvenile smolt. Image of flow over and under a roller gate

Key components of this study are the fishway for upstream passage, the fish bypass for downstream passage, the power canal and intake structure, and the roller gates.

The purpose of this study is to promote downstream fish passage through the fish bypass or over the roller gates and alter the jet trajectory into the stilling basin by proposed attached Obermeyer gates , rather than under the roller gates.

Phase 1

Phase 1 in 2006 investigated flow over and under the exiting gate, and proposed modifications using a rubber gate and mechanical deflector to change the trajectory of the jet into the center of the stilling basin to reduce harming smolt. More will be posted here latter.

Phase 2

Phase 2 in 2007 investigated the addition of Obermeyer gates to modify jet trajectories and upstream withdrawl zones.

One part of the study looked at approach velocities and velocity gradient using 2D simulations.

Velocity gradients are measured in ft/sec/ft, or just per second. We are considering a velocity gradient of 0.2 ft/sec/ft as avoidance criteria, where the juvenile smolt will try to avoid velocity gradients that exceed 0.2 ft/sec/ft. We are also considering velocity magnatudes above 2 ft/s as entrapment velocity of smolt.

More will be posted here latter.

Phase 3

This study is investigating the 3 dimensional water withdrawl options on the fish environment downstream fish passage.

    The 3D study investigated 12 scenarios.
  1. Status quo tuck
  2. Entire west gate under water, all Obermeyer control weirs disengaged
  3. Flow over 54 feet of west gate against right abutment, controlled by Obermeyer weirs
  4. Flow over 36 feet of west gate against right abutment, controlled by Obermeyer weirs
  5. Flow over 18 feet of west gate against right abutment, controlled by Obermeyer weirs
  6. Flow over 3 feet of west gate abutment right abutment, controlled by Obermeyer weirs
  7. Status quo tuck
  8. Entire west gate under water, all Obermeyer control weirs disengaged
  9. Flow over 54 feet of west gate against right abutment, controlled by Obermeyer weirs
  10. Flow over 36 feet of west gate against right abutment, controlled by Obermeyer weirs
  11. Flow over 18 feet of west gate against right abutment, controlled by Obermeyer weirs
  12. Flow over 3 feet of west gate abutment right abutment, controlled by Obermeyer weirs

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Mailing Address
Jim Higgs
Bureau of Reclamation
Mail Code 86-68460
PO Box 25007
Denver, CO 80225-0007

Phone/Fax Numbers
Phone: 303-445-2147
Fax: 720-544-6324

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Bureau of Reclamation
Bldg. 67, Rm. 152, 86-68460
Denver Federal Center
6th Avenue and Kipling St.
Denver, CO 80225-0007

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Last reviewed: 11/2/2008