Adult fish returning from the ocean have the benefit of fish
ladders at both the Rocky Reach and Rock Island hydro projects.
The ladders were constructed to assist mature salmon and
steelhead on their upriver journey to spawning grounds in the
Columbia River and its tributaries. Fish ladders were installed
when the dams were constructed. Studies of upriver migration
confirm that adult salmon pass our dams safely with no delay on
the return to their spawning grounds.
At Rocky Reach, the fish ladder leads fish through a viewing
area where visitors can “Look a salmon in the eye.”
The fish are seasonal visitors. The best months to see Chinook
salmon are May and August. Sockeye salmon are most visible
during July, and it's September for steelhead.
Helping young salmon and steelhead bypass generating systems on
their way to the ocean is a top priority for Chelan County PUD.
Effective and innovative methods have been developed through
years of research and testing. Unique systems are used at each
hydro project to take advantage of natural and manmade
At Rocky Reach, the Z shape of the dam and 29 high-powered
pumps work together. Young fish tend to congregate in one area
behind the dam. Pumps create attraction flows that draw the
fish into a collector and then into a large pipe that carries
them safely around the dam. The pipe is up to 9 feet in
diameter and nearly a mile long. Young fish make the trip
through the bypass in a matter of minutes and are channeled
into deep, swift water on the down-river side of the project
where they can continue their journey downstream.
Spilling water through gates in the dam is another way that
young fish are directed around generating systems. Spill is
especially effective for certain species of fish, and at
certain projects. Water is spilled at Rocky Reach during the
spring and early summer to supplement the fish bypass system.
At Rock Island Hydro Project, spill is the primary method of
helping young fish past the project. Years of study have
resulted in a special notched gate design at Rock Island that
spills water primarily from the top few feet of the river where
young fish tend to congregate. New over-under gates are being
installed that guide fish effectively past the dam and reduce
Even with bypass systems, some juvenile fish pass through
turbines on their way downstream. Water flow turns the turbines
at a relatively slow 90 revolutions per minute. In most cases,
fish follow the water flow through the turbines without injury.
Engineers continue to develop new turbine designs that are
increasingly fish friendly. In recent years design changes have
eliminated gaps between the turbine blade and hub where passing
fish could be injured. Fish-friendly designs are used whenever
turbines are replaced. All turbines at Rocky Reach were
replaced in a modernization project that started in the 1990s.
Modernization is underway at Rock Island and fish-friendly
turbine design is a priority there as well.
The downstream side of dams sometimes harbors unnatural numbers
of certain predator species. Predators can lie in wait for
young fish and take a high toll on the passing juveniles.
Predator control is ongoing in both Rocky Reach and Rock Island
reservoirs. At both dams, wires and streamers over the river
help deter predatory birds and fishing operations control
Continuing research is an important tool to help fish. Research
looks at every aspect of fish passage and dam operation.
Engineers and biologists use research findings to identify
migration problems, and work together to improve fish passage.
Every year, fish are tagged with electronic tracking devices so
their migration success can be measured and analyzed. Chelan
County PUD has promised no net impact to anadromous fish runs
as part of its commitment under the Mid-Columbia Habitat
Conservation Plans. Meeting that commitment is a requirement of
dam operation, and a priority of our Environmental Stewardship
Fish ladders like this one at Rocky Reach provide upstream
passage for adult salmon and steelhead.