The Wyoming Game and Fish Department (WGFD) first developed a stream classification system in 1961.The inaugural system was intended to identify and rank the most important coldwater recreational fisheries.Over time, the system was also used to assess the relative potential impacts of proposed development projects to streams. The system also was adapted as one component in a land use management program. In its previous form, streams were ranked using a combination of scores for productivity, accessibility and esthetics.
In its present form, developed in 2006, Wyoming streams are ranked according to the number of pounds of trout per mile measured in the stream segment (WGFD's Classifying Stream Fisheries). The ranking system was developed using the department’s population monitoring data and estimates of total pounds of trout per mile. Categories based on pounds of trout per mile are: Blue Ribbon (national importance) >600pounds per mile, Red Ribbon (statewide importance) 300 to 600 pounds per mile, Yellow Ribbon (regional importance) 50-300 pounds per mile, Green Ribbon (local importance) <50 pounds per mile.
The Wyoming stream classification system is referenced and used to implement the Game and Fish Commission mitigation policy. Likewise, blue and red ribbon streams are recognized as "special resources" under the Wyoming Stream Mitigation Procedure (WSMP) promulgated by the US Army Corp of Engineers (USACE). The WSMP ensures that blue and red ribbon designated streams, along with aquatic conservation areas (stream map) identified under the State Wildlife Action Plan are weighted relatively high when the USACE mitigates adverse affects under its permit authority.