It’s the end of the wettest winter in decades in the American West. And with large parts of California flooded, and many other regions buried in many feet of snow, it’s easy to forget about the epic scale of the water challenges still facing the region.

The reality, however, remains sobering. Many of America’s largest and fastest-growing cities—including Los Angeles, San Diego, Phoenix, Tucson, Denver, Salt Lake City, Las Vegas, and Albuquerque—rely on vast amounts of water from the Colorado River. Despite the storms of the past six months, that river remains catastrophically diminished, with the reservoirs fed by its flow still three-quarters empty.

This year’s onslaught of atmospheric rivers bought some precious time, but the underlying risk remains. Water sources have been depleted for decades, as a result of both rapid population growth in an arid part of the earth and overly rosy historical estimates as to the amount of water that could be safely diverted from the Colorado River each year. As long-term drought trends continue to dry the region, the water levels of the river, and, most worryingly, lakes Powell and Mead, behind the huge Glen Canyon and Hoover dams, all of which generate hydroelectric power for the region, continue to fall. True, there has been some modest increase in the lakes’ water levels in the past month or so as snowmelt from this year’s string of storms feeds into the system, but that’s a blip on what looks to be an otherwise relentless downward trend.

Too much decline, and the unthinkable happens: The water can no longer flow through the input systems in the region’s dams. First, hydroelectric power generation stops, then the river itself eventually becomes stoppered by the millions of tons of concrete and steel that make up the dams. As a result, it rapidly degenerates into what the hydrologists label a “dead pool,” a stagnant, lifeless mess downstream of the dams, a withered ghost of the great river that has roared through the American West for millions of years, carving out the canyon landscape as it goes. If this came to pass, it would be an environmental calamity at least as devastating as the Dust Bowl, and would, within a few short years, upend the lives of tens of millions of Americans.

Add into that mix the vanishing act that the Great Salt Lake has performed in recent years, leading to millions of people in the Salt Lake City region being exposed to worsening dust storms and toxic pollution from heavy metals exposed on the drying lake bed, and the West’s water woes are put in stark relief.

Yet, for years, negotiators from the seven states of the Colorado River watershed have fiddled while their Romes dried up, jockeying for position and continually putting off the hard cuts necessary to restore a water usage equilibrium. They have used gimmicky water-accounting calculations to make it appear that they are conserving more water than they actually are, and those, like California, with older water rights have been relentlessly territorial in refusing to dilute those rights to share the burden more equitably.

Now, however, it appears to be crunch time, with some hydrologists warning that the dead-pool scenario for the Colorado River could be only a handful of years away. In response to this emergency, for the first time the feds are readying to bypass the early-20th-century Colorado River Compact and impose a water distribution plan that sets aside established, and cherished, state water rights.

Last week, the Interior Department’s Bureau of Reclamation announced that, since the states have failed to come to a water conservation agreement themselves, the feds are ready this summer to impose strict mandatory water-usage cuts on the seven states—and, by extension, northern Mexico—that take water from the Colorado River. The federal government’s hope is that, while states will huff and puff about suing to block the cuts, ultimately they will either be forced to the table to negotiate their own cuts or, if they don’t, they will have to grin and bear it as the feds impose their solution.

The proposal mandates reductions on a huge scale. At a minimum, the feds envision a reduction of 2 million acre feet of water usage per year—roughly 15 percent of current Colorado River water usage in the West. If the next years are dry, however, that reduction could increase to 4 million acre feet, roughly 30 percent of the river’s water usage. It is a Hail Mary effort to save the West’s most vital ecosystem, and to give it time to recover in much the same way that the lands of the Dust Bowl nearly a century ago necessitated unprecedented interventions to replenish the topsoil and salvage millions of acres of farmland.

This reduction in available water will, inevitably, disproportionately hurt California, which, with a population of roughly 40 million, is by far the largest water user in the region, and which has seniority rights over Colorado River water owing to the fact that it achieved statehood before any of its neighbors. Depending on how burdens are distributed within the state, they will either result in huge cuts in the amount of water Southern California residents can use, or they will decimate major industries such as agriculture in particularly dry regions of the state such as the Imperial Valley. The exact distribution of these cuts will likely be determined after a public comments period on the proposals draws to a close during the summer.

Already on the front lines of climate change, the American West is now in the early days of what could well be a prolonged water war. It is pitting state against state, and states against the federal government. It threatens to undo the delicate balancing act that has long allowed states to cater both to the needs of growing urban regions and the requirements of agriculture and other water-intensive industries. There are no pain-free ways out of this crisis, so long in the making and so dire in its potential consequences. But the sooner negotiators from the seven Western states can knuckle down and reach a deal, the sooner the long, slow process of rehabbing the Colorado River and other vital waterways can begin.