Push is coming to shove on the West’s most important river.

The seven states that share water from the Colorado River are as close to open conflict over dwindling supplies as they’ve ever been. Six of them ganged up on California last week, arguing that it should bear the brunt of supply cuts because a greater share of the water evaporates before it gets that far downriver.

California is bristling at the proposal. “We didn’t just learn last year that water evaporates,” said J.B. Hamby, the chair of the Colorado River Board of California.

Another top California water official, Jim Madaffer, vice chair of the Colorado River Board of California, who represents the San Diego County Water Authority, said California has a blueprint for other states — a multi-agency, multi-year process that California used to rein in its water use two decades ago.

“California has done its part and is willing to do more, but it’s time for the other states to step up,” Madaffer said in an email.