I don't know what usually happens to the water levels between here and the end of Sept, but I just did a month long round-robin trip of Colorado, and the water isn't just low, it's really low. And its warm, too warm after lunch for my ethical position. Most, if not all of the guides I spoke with said it was a really good idea to get off of the water by Noon. That is basically what I did. Several rivers, like the Yampa in Steamboat Springs have voluntary closures. With a lot of the rivers unfishable or at the very least undesirable, it has all of those other On-vacation fisherman going to the same spots, so many places are getting a lot of pressure. At some point, I let up on my fishing schedule and became very selective. I just didn't want to harm the fish.
I know the Vacationers will be less by the end of Sept so that is a good thing. Its the worst year for snow in 20 years in CO. I'm not trying to rain on your idea, I just don't want you to be to dissapointed. Is there anyway you can look at Wyoming or Montana?
However, like Papa said, even though there were a lot of fisherman, 11-mile had enough water, so did the Dream Stream. Parts of the Gunnison were fine. My reccomendation would be to get of the beaten path as much as possible. I saw a couple of trophy-water sections that looked more like a rock concerts by the number of people that were fishing.
