Let's show you the Corps' 13 Willamette Valley Dams.
To the south, Cottage Grove and Dorena dams.
East and a little south of Eugene are Hills Creek,
Lookout Point, Dexter and Fall Creek dams.
Up along the McKenzie River are Cougar and Blue River dams.
Fern Ridge Dam is west of Eugene.
Green Peter and Foster dams are on the
South Santiam River near Sweethome,
and Detroit and Big Cliff dams
are on the North Santiam River.
Now let's look at how the system works.
The dark blue is the water that
in part is controlled by these dams.
In fact, the Corps works to manage about 77 percent
of the water flowing into the system in the Eugene-Springfield area.
Here's where it gets tricky, though.
See the light blue water on the map?
Those are uncontrolled rivers and streams
that also empty into the Willamette River Basin.
There is no way to manage that water.
It is a carefully monitored system.
Operators releasing water from the dams in the southern part of the valley
must take into account all the uncontrolled water
flowing into the system to the north.
By the time that water gets to Albany,
only about 43 percent is manageable.
In Salem, that drops to 41 percent.
And by the time that water arrives in Portland,
only about 27 percent of the water coming into the system
can actually be managed.