YOU DON'T float the Desolation and Gray Canyons of the Green River for the rapids. You go for a blissfully mellow trip through remote wilderness. During a trip down the Green one recent fall, an old friend and I didn't wear life jackets or get our feet wet for eight days. The life-jacket part I don't recommend, but the rest I do: We floated 84 miles through the Uintah and Ouray Reservation from Sand Wash to the takeout near Green River, Utah, eating lunch on the raft and passing the yellowing cottonwood leaves and the sweet-smelling tamarisk in various shades of yellow, brown, orange, and salmon.
When Edward Abbey floated the Green in November 1980, he wrote that this was "one of the sweetest, brightest, grandest, loneliest of primitive regions still remaining." Late fall is still the best time to go, in my opinion: The nights are frosty and there may be patches of snow in the shade, but the days are warm and (most of the time) you can get by wearing just a T-shirt and long pants. You can eat well; on an oar-rigged raft trip you don't need to skimp on gear or rations. You can also camp on ample silt banks and and hike up side canyons to look for tracks of bear and mountain lion, or scout for 1,000-year-old petroglyphs left by the Fremont Indians.
After Three Fords rapid, at mile 59, you pass out of Desolation Canyon and into shallower Gray Canyon. Look upriver here and you'll see a great contrast between the red-stained Wasatch formations you're leaving behind and the low, rounded, gray-green hills of the Mesa Verde Group ahead. The mild rapids turn to riffles and become fewer and fewer from here to the takeout.