Arizona should start now to make sure our kids and grandkids will be drinking desalinated seawater — and other new water supplies — to avoid a crisis, a state agency urges.

The other future sources of drinking water for Arizonans should include treated wastewater, desalinated brackish groundwater and rain caused by cloud seeding, the Department of Water Resources says in a new report.

Otherwise, a water shortage looms as soon as 25 years from now as our population grows, the officials say.

“Desalination is something tangible. It’s being done elsewhere in the world, and while pulling it off will be a very complicated thing, we thought it was more politically feasible than importing supplies from far away such as the Columbia or Missouri rivers,” said Michael Lacey, the department’s interim director.

But desalination is controversial because of its high cost — likely in the billions of dollars — energy use and environmental impacts.

Before investing too much in one water-supply alternative, the state needs an objective analysis by experts who don’t have a clear stake in the outcome, says Wendell Ela, a University of Arizona desalination expert.

“Desalination of seawater is certainly a technologically feasible option, but is not yet demonstrated to be the most practical, economic or politically viable option,” he said.

• Turn to Page A18 to see how desalination would work and what it might mean to you.