A landscape photo of sand creek with lush green vegetation bordering the creek.

Stream categorization

The Wyoming Game and Fish Department first developed a stream categorization system in 1961. The inaugural system was intended to identify and rank the most important cold-water recreational fisheries. Over time, the system also was used to assess the potential impacts of proposed development projects on streams.

Stream categorization and mitigation

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
(Wyoming Game and Fish Department's System for Categorizing Stream Fisheries). The ranking system was developed using the Wyoming Game and Fish 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) >600 pounds per mile, Red Ribbon (statewide importance) 300 to 600 pounds per mile, Yellow Ribbon (regional importance) 50 to 300 pounds per mile, Green Ribbon (local importance) <50 pounds per mile.


The Wyoming stream categorization system is referenced and used to implement the US Army Corps of Engineers (USACE) Wyoming Stream Mitigation Procedure (WSMP). 
Blue and red ribbon streams are recognized as "special resources" under the WSMP. 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.

Stream categorization map