Key Concepts

Existing Uses: The Uses Already Attained by a Water Body

Existing uses (defined in 40 CFR 131.3(e)) are uses that were "actually attained" in a water body on or after November 28, 1975—the day EPA promulgated the original water quality standards regulation.

Determining existing uses that have been actually attained in a water body may involve evaluating data on the following:

• Historical/current water quality.
• Historical/current biological condition.
• Pattern, frequency, and type of use.

Video Clip. View a 1-minute video clip from the classroom session on existing uses.