Historic habitat is flooded. Salmon and trout generally favor habitat in wide, flat river valleys. These valleys accumulate gravel for spawning and provide quiet backwaters for resting and feeding. These habitats in the Bull Run watershed were also good locations for constructing dams. Much of the historic habitat above the dams is now flooded by the reservoirs.
Flow is reduced.
Below the dams, flow in the river channel is limited during the summer. More than 800,000 Oregonians use a total of 150 to 200 million gallons from the watershed on warm summer days. Water is warmer. As the water slows and pools up behind the dams, it absorbs heat from the sun. The water warms even more in the rocky, shallow pools below the dams.