The Central Arizona Project's board voted at its early-November meeting not to renew funding for the next phase of a cloud seeding collaboration that CAP has supported since 2007. The program releases particles into clouds over Colorado, Utah and Wyoming to coax additional snowfall in the mountains where most of the Colorado River originates.

CAP operates a 336-mile canal system that carries river water across the desert to Arizona's two largest population centers. For years it has joined water agencies in Las Vegas and Los Angeles, along with major Southern California farming districts, in sending about $1.5 million annually to upstream seeding work. Under the proposed new terms, each agency's contribution would have been capped at $525,000 in 2027 and gradually increased to $750,000 by 2036.

Board members who opposed renewal questioned whether Arizona ratepayers would see a return. "It's hard to see how this is really going to help our customers, especially in the environment that we're working in right now, and our taxpayers," said Alexandra Arboleda, who voted against the measure.

Stephen Miller, another board member who voted no, said the science supports cloud seeding in principle but the results are hard to quantify. "The science says it works, but the outcome is difficult to really measure at the end of the day," he said. "That's where the skepticism comes in."

CAP staff pushed back, pointing to studies suggesting seeding can increase snowpack by as much as 20% above baseline. Nolie Templeton, the agency's Colorado River policy and analysis manager, called it one of the most cost-effective ways to add water to the basin. "Everyone benefits from a healthier Colorado River basin system," she said.

The decision comes amid a deepening dispute between the Lower Basin states — Arizona, California and Nevada — and the Upper Basin states of Colorado, New Mexico, Utah and Wyoming over how to share a shrinking river. Negotiations collapsed after years of talks, prompting the federal government to impose mandatory cutbacks on the Lower Basin without requiring new mandatory reductions from the Upper Basin. Arizona and CAP have both moved to join a lawsuit challenging that plan.

Some board members worried that paying for snow in the Upper Basin could strengthen states that are now adversaries in court. "My biggest concern is just how will we be treated by the Upper Basin? Will we get to see any of that extra 10%?" said April Tornquist, who voted to renew funding.

Arizona's Lower Basin allies had urged CAP to stay in. Both the Southern Nevada Water Authority and a group of six California water agencies sent letters encouraging the board to continue supporting the program.

Cloud seeding is not a cure for the region's long-term water deficit. Snowmelt remains the dominant source of inflow to Lake Powell and Lake Mead, and even a wet October that added roughly 850,000 acre-feet to Lake Powell pales next to the roughly 5 million acre-feet that flow in during an average spring. Templeton has said it would take about five consecutive winters of above-average snowfall to bring Lake Powell to half full.

An acre-foot is roughly the amount of water needed to cover a football field one foot deep — about a year's supply for three Phoenix-area homes, according to the Arizona Department of Water Resources.