Expert: Population growth, warming imperil CAP supply

You could call Tim Barnett the Southwest's water Cassandra — gifted with visions of the future, but doomed to be ignored.

Since the middle 1980s, many climatologists, hydrologists and other scientists have predicted that global warming and other forms of climate change will mean less water for the Colorado River and, by extension, the Central Arizona Project, the $4 billion collection of canals and pipelines that is Arizona's water lifeline.

But few experts have belted that message as forcefully as Barnett, a marine physicist at Scripps Institute of Oceanography in San Diego.

His warnings have been met with doubt by some of the West's water managers who have long felt they could plan, design, engineer and manager their way out of a future water crisis caused by the collision course between population growth and the region's aridity. Some scientists questioned Barnett's first study, which predicted that Lake Mead and Lake Powell had a 50 percent chance of drying up by 2021 due to human-caused climate change. In the second study, like the first co-authored with fellow Scripps researcher David Pierce, he predicts that by 2050 the river could see water flow cut in half in some years due to human-caused climate change and natural variation in precipitation.