‘We’ve known for literally decades that climate change is going to affect water availability in the Colorado [River] and in the Western U.S. in general. And we’ve wasted that time.’

If you walk to the edge of Lake Mead, on the border between Nevada and Arizona, you can stand on a rocky shore that used to be more than 100 feet below water. After 23 years of drought and increasing demand for water, the lake keeps shrinking. Satellite photos show the stark difference between the way the reservoir looked in 2000—dark blue and sprawling—and what’s left now.