California is expected to officially start up its second desalination plant in April, which takes seawater and makes it potable. The first one opened in December 2015 in Carlsbad that is near San Diego while the next one will be in Santa Barbara that is north of Los Angeles. And 15 more are on the table there. Is this a global solution for the billions without access to potable or sanitized water? Can desalination be done in a way that is minimizes harm to the ocean and that uses clean energy to run its operations?

The water level dropped Monday behind the nation’s tallest dam, reducing the risk of a catastrophic spillway collapse and easing fears that prompted the evacuation of nearly 200,000 people downstream. As the day began, officials from the California Department of Water Resources prepared to inspect an erosion scar on the spillway at the dam on Lake Oroville, about 150 miles northeast of San Francisco. Authorities ordered evacuations Sunday for everyone living below the lake out of concern that the spillway could fail and send a 30-foot wall of water roaring downstream.

Thousands of people fled areas downriver from Lake Oroville on Sunday after a secondary spillway at the swollen reservoir was compromised, raising fears of a collapse that might unleash disastrous flooding. By late Sunday, after whole towns had emptied out, officials said the immediate danger appeared to have passed. Evacuation orders, however, remained in place until they could be sure. “There are still a lot of unknowns,” Sheriff Kory L. Honea of Butte County said at a news conference.