bd,
I don't get up to the Obey as often as I would like to, but I did float it two weeks ago from the dam down to the park. Dale Hollow was running one generator until 9:00 AM - we got in behind it on falling water and it fell out pretty quick. Wolf Creek was running one or two generators that day. However, the river still seemed to get backed up up about 1.5 miles below the island. My guess is that 3 or more generators at Wolf Creek would start to back up the river all the way to the island, but that is just a guess. The generation last year at Wolf Creek very often kept the Obey heavily backed up from the summer through the end of the year - even under generation from Dale Hollow.
The fishing was good - nothing huge, but the trout were healthy with plenty of color.
Hope this helps. Maybe someone who has floated or waded the Obey under a wider range of conditions can chime in.
Hilljack