Colorado

My buddy and I ran Westwater 12/6/20 and 12/18/20.

12/6: air temp was 11 degrees F at launch time. We were cold, but, despite iced over eddies and floating slush, the run was clean, and we laughed all the way home.

12/18: air temp was 31 degrees F at launch time. Right around Little Wild Horse Rapid, we saw our first river-wide ice bridge. We portaged on the ice without incident. We crossed half a dozen other ice bridges before we entered the canyon.

The rapids are always a blast, and we had no problems. But, as the water slowed around the bend below Last Chance Rapid, we found ourselves facing an ice field stretching on as far as we could see: at least 2-3 miles. We attempted to walk this ice field but it turned to soft slush about a half mile in. It wasn't humanly possible to paddle, wade, swim, walk, crawl, or generally move across the slush. We pulled our boats out river right (hoisted up the cliff for me, ouch), and hiked 15 miles back to the put-in.

I did not recognize that the Colorado would form ice in these quantities. Although we were fine, we (1) were healthy and well-prepared, and (2) were lucky. I have since seen posts rumoring that ice bridges can form INSIDE the main canyon, which sounds like an incredible, terrifying hazard.

My recommendation to anyone attempting a winter run: check the Cisco gauge. If you see water temps consistently a few degrees over 32, a run may be awesome: we saw this before our 12/6 run. If you see the water temp flatlining at 32, think about doing something else, unless you're willing to risk a helluva day.