Spilling water over hydroelectric dams, rather than running it through turbines, is generally seen as the safest method to get the young salmon and steelhead past the dams on their way to the ocean. NOAA Fisheries’ biological opinion for the Federal Columbia River Power System calls for spilling 24 hours a day at all eight dams from early April through the end of the fish migration in August.
In addition to spill, the Corps of Engineers has made major structural improvements at the dams to make them safer for fish passage. All eight dams now have surface passage routes that improve the effectiveness of the spill by attracting smolts to that area, using less water and generally achieving better survival than conventional spill. Watch a video to find out more. The FCRPS is also operated to provide spring and summer flow augmentation, further improving conditions for migrating fish.
Spill levels are tailored based on test results to optimize fish passage given the configuration of each dam. To date, performance testing shows that all dams are on track to meet biological opinion standards of 96 percent survival for spring migrating fish and 93 percent for summer migrants.
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The Corps conducted summer performance standard testing at two of the eight dams in 2013. In 2014, the Corps will conduct performance standard tests at McNary in the spring and McNary and John Day dams in the summer. |
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Because of operational and structural improvements at the dams, juvenile fish survival through all eight dams is as good as or better than in the 1960s, when there were four federal dams on the lower Columbia and Snake rivers. Read more about 2015 juvenile Snake River steelhead and chinook survival through the hydrosystem here.
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Spill for fish passage, at Ice Harbor Dam on the Lower Snake River |