by
Rachel Hansen | Nov 29, 2023
More than 93% of young Chinook safely passed Rocky Reach Hydroelectric Project last spring. The results represent the most successful survival study of yearling Chinook in the 21-year history of the Rocky Reach Habitat Conservation Plan.
About 1,130 yearling Chinook were tagged and released from April to May. The fish took between 17.8 hours to 38 days to travel from the tailrace of Wells Dam to about 1,000 feet below Rocky Reach.
“The time it took was definitely surprising to us,” said Lance Keller, senior fisheries biologist at Chelan PUD. “That shows us that we have good survival conditions in the reservoir of Rocky Reach Hydro Project.”
The study showed researchers how juvenile salmon pass through Rocky Reach. Last spring, more than 45% of the tagged juvenile salmon chose the juvenile bypass system. Those fish that use the bypass have a 100% survival rate. The surface collector, located at the corner of the dam, uses up to 29 special pumps to attract fish into a 9-foot diameter tube that carries fish across the entire length of the dam before depositing them at the east side of the Columbia River.
Tagged fish also passed through the powerhouse, which is comprised of 11 generating units. Many of the turbines have been improved over the years to be more fish-friendly. Last spring, about 14% of juvenile salmon passed through generating units 1 and 2 with 98.7% survival. About 37% passed through generating units 3-10 with 93% survival.
“Looking at these routes of passage compared to previous years, it appears we were successful in getting fish in the surface collector in 2023, which is how we designed Rocky Reach to operate,” Keller said.
The study also followed previously tagged adult salmon headed upriver from Rocky Reach to Wells Dam. Of the 193 adult fish detected, all but one completed the journey.
Overall, the combined adult and juvenile survival was 93.54% at Rocky Reach, which is above the HCP requirement to achieve 91% combined survival.
Chelan PUD achieved similar survival rates for yearling Chinook – 94.45% -- at Rock Island Hydroelectric Project in 2021.
The survival studies are required by the habitat conservation plans (HCP) for Rocky Reach and Rock Island hydro projects. Chelan PUD developed the plans cooperatively with state and federal fisheries agencies and tribes. The next Rocky Reach study is planned for 2033.
Chelan and Douglas PUDs are the only hydropower producers in the nation with habitat conservation plans under the Endangered Species Act. The plans commit the PUDs to a 50-year program to ensure that its hydro projects have no net impact on the upper Columbia River salmon and steelhead runs.
No net impact is accomplished in three ways: strict standards for juvenile and adult survival through the project, hatchery fish production to account for juvenile fish mortality that occurs at the project, and funding for tributary habitat enhancements and restoration. The PUD spends about $32-37 million annually for these programs combined. Fulfilling these commitments under the HCPs, while generating carbon free power for our local ratepayers and the region, is Chelan PUDs way of demonstrating how hydropower and salmon can co-exist.
“This is something we can all be very proud of,” Keller said. “When we look at the work we’ve done on the units to boost efficiency, the work we’ve done with northern pike minnow control, and a whole host of tools we have in the HCP, they are indeed working.”
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