Some of what we call lakes here are actually reservoirs behind flood control dams. This is the case of Dexter Lake which stands behind Dexter Dam on the Willamette River about 25 miles from Eugene. The lake is often used for recreation and as a practice site for the University of Oregon rowing team. I went to school in Lowell which now sits along the shore of Dexter Lake. It wasn't there when I went to school there.
This photo of a boater on Dexter Lake is made more dramatic by the early morning light.