This river is in my home country and is one of the most beautiful rivers in one of the most beautiful settings in the country. A great trout, steelhead, and smallmouth bass river. This deep canyon is also home to a variety of big game as well as upland birds. It is not unusual to see deer, elk, big horn sheep, bear, chukars, grouse, coyotes, mountain lions and cowboys horseback roaming its steep rugged hillsides. It is best known for its dry fly steelhead fishing in the fall. The best top water steelheading is in late September through October, but the river fishes through the winter and into mid-April when it closes, that is if it doesn't ice over during December and January. February through mid-April can be awesome using nymphing techniques. The best fishing during the early spring is between Cougar Creek and Boggan's Oasis. At this time of year, the Washington fish are held up above and below the Cottonwood Creek Acclimation Pond. There can be as many as 6,000 fish holding in this approximately 4 mile section of river, and egg patterns can fish well. The river flows can be kind of volatile this time of year if you get an early run-off. I have seen it go from about 1500 cfs to 10,000 cfs pretty darn fast and look like chocolate pudding.
The best smallmouth bass and rainbow trout fishing starts in June when the river opens again and extends through the summer. Fishing is closed mid-April to the first Saturday of June to take the pressure off the spawning steelhead. Both smallmouth and rainbows can also be taken on dries throught the summer. Air temperatures in the canyon in late July and August can easily exceed 100 degrees, so you want to have plenty of water and sun screen. A big hat is also very nice. Buckaroos don't wear big hats just for looks; in fact, their name for the hat is "my shade."
I don't talk much, but I can talk about this river for at least 30 minutes. My Uncle and Aunt owned a ranch at Enterprise, OR just south of the river, and I spent a lot of summers there. It is definitely one of my favorites along with the Methow and Klickitat.
Grande Ronde Flow:
http://waterdata.usgs.gov/or/nwis/uv/?site_no=13333000&PARAmeter_cd=00065,00060