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. Salmon and trout prefer cool water. Warm water stresses the fish, and temperatures above 70 degrees can be lethal. Like many other rivers and streams in Oregon, the lower Bull Run River sometimes reaches these lethal temperatures.