In Oregon, as in many other states, some of the best information for wild trout anglers originates in the water quality world.
In the early-2000s, Oregon adopted surface water classifications based on “designated” uses. The sensible idea behind such classifications is that, for example, the regulations governing what you can do 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 rules.
Among Oregon’s designated uses were spawning, migration, and rearing habitat for salmon, bull trout (which require even colder water) as well as resident trout (both native and exotic).
During the analysis that accompanied the promulgation of these new regulations, the USEPA prepared a state-wide series of maps showing the designations. What is unique about these maps is a) they’re state wide, and b) are really the only comprehensive source that includes resident trout. A detail from one map is shown below.
In this map, gray is non salmonid habitat. Blue is rearing water for bull trout. Other maps code as many as six different uses.
The maps are nicely rendered PDFs. The streams are rendered using vector graphics, which means you can zoom in as much as you need without pixellation. There are one or two maps per basin.