To help salmon and trout return from the ocean to their native streams to spawn, the dams have long operated fish “ladders” - gradually stepped-up watercourses that help the fish get around the massive vertical dams. But once hatched, the young fish have to get back downstream as well. Each spring and summer, juvenile salmon and steelhead attempt to navigate through an obstacle course of hydroelectric dams in their downstream imigration. Mortality in the early life stages is normally high due to factors including natural predation and human induced changes in habitat. By the time dams were built, the salmon population was severely depleted. To reverse the declining fish populations, a federal mandate now requires the power plants to shut down the power production during the peak migratory season or develop “fish friendly” solutions.
To protect fish without losing valuable power, the operator at Rocky Reach Dam constructed a bypass powered by 29 pumps. A surface collector to guide fish around a hydro project was developed and tested by Chelan County PUD engineers and biologists. The system is based on sonar studies showing that fish generally travel in the upper 60 feet (18.3 metres) of the river. The surface collector system appeals to the natural instinct of juvenile fish to stay in that zone and follow the water flow - which in this case is created by powerful pumps from Xylem’s Flygt team. The water directs the fish into a bypass pipe, which moves them safely around the dam.