Several years back, on a float trip in northern Utah where the murky currents of the aptly named Red Creek dump into the Green River, I had an epic day of fly fishing.
A summer squall had moved across the steppe country the day before, and Red Creek was brimming. The Green, cold and clear in its A section below Flaming Gorge Dam, collided with the muddy flows of the tributary and created a visible line between clean and dirty water that meandered downstream for a half a mile.