Flow Field Within the Vertical Slot of a Fish Passage: the Effect of Turbulence, Velocity and Slot Length and the Design of a Lamprey Passage System at the John Day Dam

To understand the flow conditions encountered by migratory fish within a vertical slot section of fishways, measurements were made in an experimental flume where velocity, turbulence, and slot length were manipulated. The results show that turbulence intensity increases with slot length and mean flow velocity regardless of turbulence treatment. The high velocity zone moves from downstream to upstream by adding a turbulence-inducing wall upstream of the slot. High turbulence zones preferentially formed toward the entrance of the slot for the control treatment whereas high turbulence zones were distributed through the entire slot in the turbulence treatment. These changes likely affect upstream migrating fish. Observations of Pacific lamprey passing the experimental serpentine weir show that they chose paths with low turbulence under the high velocity treatments. The design and installation of a Lamprey Passage System at the North Fishway on the John Day Dam are also described.