Roughly 1,000 years ago, ancient peoples carried more than 200,000 heavy timbers entirely on foot to a site in the modern-day Four Corners region called Chaco Canyon. CU Boulder researchers think they know how such a feat of human endurance may have been possible.
The Colorado River is approaching a breaking point, its over-tapped reservoirs dropping. Years of drying have taken a toll at the river's source in the Rockies.
The US Bureau of Reclamation Tuesday said water shortages in the Colorado River have passed a threshold leading to new water restrictions as seven states involved in the Colorado River Compact have failed to reach a new deal to replace the one signed 100 years ago.