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and those through which fish passage is provided but at reduced levels from natural 
conditions.
C.
The dams impede juvenile and adult migrations to and from the ocean by their physical 
presence and by creating reservoirs. The reservoirs behind the dams slow water 
velocities, alter river temperatures, and increase predation potential. Reduced water 
velocity increases the time it takes juveniles to migrate downstream, higher water 
temperatures may have adverse effects on juvenile and adult behavior, and predators 
find prey more easily in slower moving water. The Corps operates a series of eight dams 
on the lower Columbia and Snake rivers that affect the habitat and migration of salmon. 
These dams are equipped with adult and juvenile fish passage facilities. Adult fish 
ladders at all eight lower Columbia and Snake dams were integrated into the design of 
the dams beginning with Bonneville in 1938. These ladders consist of a series of steps 
and which provide a gradual upward climb over the dams for returning adults. To steer 
the adults to the ladders, "attraction" flows at the downstream ladder entrances simulate 
conditions that would be found at the base of natural waterfalls. The concept has proved 
effective for adult fish passage.
D.
Currently, juvenile fish can migrate past the dams by several routes: through the turbine; 
through the juvenile fish bypass system; or over the dam spillway. Some fish are 
transported past the dams by barge and truck under the juvenile fish transportation 
program. At the Dalles Dam, fish are bypassed through the ice and trash sluiceway. The 
juvenile fish bypass systems in place at seven of the eight lower Columbia and Snake 
River dams guide fish away from turbines by means of submerged screens positioned in 
front of the turbines. The juvenile fish are directed up into a gate well, where they pass 
through orifices into channels that run the length of the dam. The fish are then either 
routed back out to the river below the dam, which is called "bypassing" or, at the four 
dams with fish transport facilities, fish can be routed to a holding area for loading on 
specially equipped barges or trucks for transport downriver. The juvenile bypass systems 

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