The designated use of a waterbody may be modified if it can be demonstrated that it is not an existing use, is not attainable, or is not sufficiently protective. A designated use reflects the ability of the waterbody to support the use, even if it doesn’t currently exist. Individual surface waters in Wyoming will have multiple designated uses where the most sensitive use determines the highest level of water quality protection. Uses that currently exist on a waterbody or have existed on a waterbody at any time since November 28, 1975, cannot be removed or downgraded.

Proposed changes to aquatic life, human consumption of fish, recreation, or terrestrial wildlife designated uses on surface waters of the state subject to the federal Clean Water Act, that would result in less stringent water quality criteria, require the completion of a Use Attainability Analysis (UAA). A UAA is a structured scientific assessment of the designated uses a waterbody could support considering its inherent physical, chemical, and biological characteristics; economic considerations; and the influence of both point and nonpoint sources of pollution. 

Proposed changes to other designated uses or those assigned to surface waters of the state not subject to the federal Clean Water Act that would result in less stringent water quality criteria, require the completion of a use and value demonstration which may be satisfied through completion of a UAA.

Adoption of all proposed changes to designated uses requires formal rulemaking to amend Wyoming’s Surface Water Quality Standards (Chapter 1, Wyoming Water Quality Rules). The document Wyoming Surface Water Designations, available in the Standards Resources and Guidance tab above, or Recreation Designated Use Web Map are updated as designated use changes are approved. 

The document Options to Modify Water Quality Standards (available in the Standards Resources and Guidance tab above) describes considerations for when a change to a designated use may be appropriate. For more information contact Eric Hargett (eric.hargett@wyo.gov) or 307-777-7079.