I drove to the bluff overlooking the “Gunny” to process the sad news — news that hasn’t yet been made official — that by October a big portion of the lower Gunnison River in western Colorado will be dry. The official term is “fully dewatered.” Monsoons were supposed to be heavy this year. As I looked down at the river in late August, clouds in the distance appeared almost monsoonal. Wisps of rain streamed out, but they evaporated before reaching…