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Lamprey Flume System Installed

Jun 19, 2013

On June 4, 2013 the U.S. Army Corps of Engineers completed a Lamprey Flume System at the Washington Shore fish ladder entrance of Bonneville Dam. This is the largest and most complex structural improvement yet made for lamprey and is significant due to the fact that historically, lamprey have had the most trouble successfully navigating the fish ladder on the Washington Shore.

The Lamprey Flume System is unique in that it has lower and upper ports that span the entire fishway entrance, which are designed to funnel lamprey into the flume system allowing adults to avoid the difficult passage environment located within the Washington Shore fish ladder.

Since becoming fully operational, multiple lamprey have been observed using the system. Ideally this number will increase as the lamprey run at Bonneville builds towards its historical peak in mid to late July. Lamprey returns have increased each of the last two years.

It will take a unique combination of structural and operational fixes at mainstem and tributaries dams to improve the passage environment for lamprey. Hopefully the lessons learned from the implementation and monitoring of the Bonneville Washington Shore can be used to benefit lamprey throughout the Columbia River basin.

Bonneville Dam Washington Shore Fish Ladder Lamprey Flume System

Bonneville Dam Washington Shore Fish Ladder Lamprey Flume System – image courtesy US Army Corps of Engineers


  1. Upper entrance
  2.  Lower entrance
  3. Thimble, closure gate, and elbow flume section
  4. Filler plate
  5. Flow splitter flume section
  6. Downstream “school bus” flume section
  7. Upstream “school bus” flume section
  8. Lamprey Flume System and Lamprey Passage Structure
  9. Gravity water supply pipe