Section 16(b) of the Wild & Scenic Rivers Act, defines a “river” as “a flowing body of water . . . or portion, section, or tributary thereof. . . .” “Free-flowing” is defined as “existing or flowing in natural condition without impoundment. . . .” Therefore, any section of river with flowing water meets the technical definition of free flowing, even if impounded upstream.
Source
Interagency Wild & Scenic Rivers Council