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A photo of a dam just outside of McMinnville. The photo shows the embankment, emergency spillway and outlet.
Dams are hydraulic structures built above the natural ground grade line and are used to impound water.  Dams can include wastewater lagoons and other hydraulic structures that store water, attenuate floods, and divert water into canals. Many traditional dams are constructed on stream channels to form reservoirs.

Most dams are built of compacted soil or rock fill and are called embankment dams; a few are made of lumber.  Concrete dams, although less common, are some of Oregon’s largest dams.  Owners of dams include homeowners, farmers, irrigation districts, private industry, municipalities, associations, and public agencies.  Some of Oregon’s dams are more than 100 years old.