In Colorado, rivers flow not only down mountain slopes but beneath them, across them, and through them. Nearly four dozen canals, tunnels, and ditches in the state move water out of natural drainages and into neighboring basins. Some snake across high passes. Others pierce bedrock. All manmade water courses, meant to supply farming, manufacturing, or household use, eventually become so familiar they become part of the landscape. But old infrastructure can come to life in different form.