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 conditions.
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 harmful gases.
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 pikeminnow populations.
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 mission.