This is a cutout view of a river. The dark
blue water is water that flows into the drainage system behind the dams. The light blue water
is water that flows into the system from uncontrolled rivers and streams. When the rains come and
the uncontrolled streams fill the Willamette’s system, the Corps holds water behind the dams.
As the river level drops, the Corps releases the water into the system.
Every dam has at least two ways to release water. Some, like this dam at Lookout Point,
have three. For dams that generate electricity, water
passes through the powerhouse and into the river below the dam.
The second option at Lookout Point – and the primary route for dams without powerhouses-
is the regulating outlet. This is a gated route through the dam itself. The spillway
gates, near the top of the dam, are used to move water through the dams when other routes
are unavailable or when the reservoir gets too full. These gates are always a back-up
system and are not used very often-or even every year.