• Juvenile salmon and steelhead pass the dams through many different routes

    The latest test results are showing that surface passage, combined with refined spill operations, has reduced the percentage of fish that go through powerhouses, turbines and bypass facilities, decreased fish travel time through the system and increased overall dam survival. Read more here.


    Juvenile fish pass the dams by many routes: through juvenile bypass systems, spillways and turbines, or by collection and transport in barges or trucks. Adult fish migrate back to their spawning grounds using fish ladders, also called fishways. 



    Today, major improvements have rendered the lower Columbia and lower Snake River dams more fish friendly for juvenile and adult fish. Juvenile survival through all eight dams and reservoirs is higher than when there were four dams.  Adult survival through the dams is similar to a natural river.

    Tests at Lower Monumental Dam on the lower Snake River in 2012 estimated that almost 80 percent of the juvenile spring chinook passed the dam through spill (surface weir or spillway), 16 percent through the bypass system, and 5 percent through the turbines. Overall survival through all routes was 98.7 percent. See findings from similar tests at all eight lower Snake and Columbia River dams

    The FCRPS BiOp includes dam survival performance standards (through all passage routes) of 96 percent for spring migrating fish and 93 percent for summer migrating fish. Juvenile dam survival estimates of 86 to 99 percent have been demonstrated at all Snake and Columbia River dams.

    The Corps has invested over $1.8 billion in fish passage improvements at the FCRPS dams since 2001, resulting in significant survival improvements. 

  • Adult Fish Passage Routes
    Adult Fish Ladders are helping fish returning from the ocean to their spawning grounds pass the dams.
    Juvenile Fish Passage Routes

    SpillSpilling 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.


    Surface passage such as spillway weirs and the Bonneville corner collector make spill more effective by providing more natural river passage conditions. NOAA researchers believe that surface passage structures have helped reduce juvenile fish passage time through the hydrosystem. 

    Screened juvenile bypass systems are in place at seven of the eight lower Columbia and Snake River dams. These bypass systems guide fish away from turbines by means of submerged screens installed in the turbine intakes.  The Corps continues to make modifications to juvenile bypass systems to improve survival.

    TransportationAbout a third of the juvenile chinook and steelhead that migrate through the lower Snake and Columbia rivers are transported downriver by barge. The survival rate for juvenile fish that are barged is close to 100 percent.