The Johnday river has some of the worst snakes, they tend not to rattle, but I haven't seen a swimmer there yet.
Back on topic, I would look up to see what guys in Montana do. I imagine a lot of hopper patterns later in the year, streamers that look like chub minnow and crawdads would be best on the Owyhee. Also, those rivers usually have good populations of tricoptera and rock cased caddis (at least Johnday does). If the water is low, just stand in the middle above a run going into a pool and swing your fly from side to side releasing about 3' of line after crossing the river. It's almost like cheating, except no bait so you're okay (bait is cheating).
Back on topic, I would look up to see what guys in Montana do. I imagine a lot of hopper patterns later in the year, streamers that look like chub minnow and crawdads would be best on the Owyhee. Also, those rivers usually have good populations of tricoptera and rock cased caddis (at least Johnday does). If the water is low, just stand in the middle above a run going into a pool and swing your fly from side to side releasing about 3' of line after crossing the river. It's almost like cheating, except no bait so you're okay (bait is cheating).