WA Fish Beneficial Use (EPA/Ecology)

posted in: Data, WA | 0

WA Beneficial usesIn the State of Washington, as in many others, some of the best information for wild trout anglers originates in the water quality world.

In the mid-2000s, Washington adopted surface water classifications based on “beneficial” uses.  The sensible idea behind such classifications is that, for example, the standards for what is acceptable in a headwater stream that is spawning habitat for an endangered salmonid species ought to be quite different from a warm-water, 8th-order river that flows through agricultural land.  In this scheme, you can designate a use for one stream as “salmonid spawning” and the other as “agricultural irrigation”, and apply different standards.

Among Washington’s designated uses are ones designed to protect the salmonid population.  Designated streams don’t necessarily hold populations of salmonids: the segments were decided based on stream surveys, models, and professional judgement to assign categories to every stream, many of which have never been surveyed.  These data, therefore, provide an interesting counterpoint to the species distribution data from WDFW which show only streams surveyed to hold trout.  With the standard distribution data, you don’t know whether a stream not included was surveyed and did not hold trout, or was simply never surveyed.  These Core Habitat maps provide some insight into the difference.

Water temperature (based on 7 Day Average Daily Maximum Temperature in the warmest month of the year).  Categories marked with an asterisk may have more stringent requirements during the projected critical times for salmonid spawning.


Highest 7-DADMax
Char Spawning and Rearing*
12°C (53.6°F)
Core Summer Salmonid Habitat*
16°C (60.8°F)
Dark Orange
Salmonid Spawning, Rearing, and Migration*
17.5°C (63.5°F)
Light Orange
Salmonid Rearing and Migration Only
17.5°C (63.5°F)


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