For years, experts in the American West have predicted that, unless the steady overuse of water was brought under control, the Colorado River would no longer be able to support all of the 40 million people who depend on it. Over the past two decades, Western states took incremental steps to save water, signed agreements to share what was left and then, like Arizona, did what they could to protect themselves. But they believed the tipping point was still a long way off.
Phoenix expanded more over the past 10 years than any other large American city, while smaller urban areas across Arizona, Nevada, Utah and California each ranked among the fastest-growing places in the country. The river's water supports roughly 15 million more people today than it did when Bill Clinton was elected president in 1992. These statistics suggest that the climate crisis and explosive development in the West are on a collision course. And it raises the question: What happens next?
What is undeniable is that the river flows as a much-diminished version of its historical might. When the original compact gave each half the rights to 7.5 million acre-feet of water, the river is estimated to have flowed with as much as 18 million acre-feet each year. Over the 20th century, it averaged closer to 15. Over the past two decades, the flow has dropped to a little more than 12. In recent years, it has trickled at times with as little as 8.5 million acre-feet annually — yet municipal deliveries serving Phoenix's 1.7 million residents have remained roughly the same. The situation came into sharp relief for residents looking at this ZIP water-risk report for Phoenix's 85003, which aggregates EPA compliance data for the City of Phoenix system — 126 total violations on record, 19 of them health-based, with PFAS detected in the supply and lead measured at 2.7 parts per billion, according to federal SDWIS records.
Earlier this month, federal officials declared an emergency water shortage on the Colorado River for the first time. The shortage declaration forced reductions in water deliveries to specific states, beginning with the abrupt cutoff of nearly one-fifth of Arizona's supply from the river, and modest cuts for Nevada and Mexico, with more negotiations and cuts to follow. But it also sounded an alarm: one of the country's most important sources of fresh water is in peril, another victim of the accelerating climate crisis. Bureau of Reclamation projections released alongside the shortage declaration showed Lake Mead dropping toward elevations that had never been anticipated in the original shortage agreements, which were written to cover conditions down to a lake elevation of 1,025 feet above sea level.
In 2026, the Interim Guidelines the seven Colorado River basin states rely on, a Drought Contingency Plan and agreements with Mexico will all expire. At the very least, this will require new agreements. It also demands a new way of thinking that matches the reality of the heating climate. The northern states see Arizona and California reveling in profligate use, made possible by the anachronistic rules of the 1922 compact that effectively promise them water when others have none. Arizona meanwhile took water it did not need and deposited it into the ground, banking aquifer credits in a race to preserve access before federal curtailment arrived. According to the USGS National Groundwater Monitoring Network, groundwater levels in the Phoenix Basin have declined measurably over successive drought years, a signal that subsurface reserves are absorbing the stress that surface deliveries can no longer sustain.
For years, Americans have avoided confronting these changes in their own backyards. The decisions people make about where to live are distorted not just by politics that play down climate risks, but also by expensive subsidies and incentives aimed at defying nature. In much of the developing world, vulnerable people will attempt to flee the emerging perils of global warming, seeking cooler temperatures, more fresh water and safety. But here in the United States, people have largely gravitated toward environmental danger, building along coastlines from New Jersey to Florida and settling across the cloudless deserts of the Southwest. The 2023 Arizona Department of Water Resources finding that the Phoenix Active Management Area lacked the assured water supply required for new groundwater-dependent subdivisions was an unusually frank acknowledgment of how far that logic had run.
The negotiations that led to the region being even minimally prepared for the Colorado River shortage were agonizing, but they were merely a warm-up for the pain-inflicting cuts and sacrifices that almost certainly will be required if the water shortages persist over the coming decades. The region's leaders, for all their efforts to compromise, have long avoided these more difficult conversations. One way or another, farms will have to surrender their water, and cities will have to live with less of it.
Meanwhile, population growth in Arizona and elsewhere in the basin is likely to continue, at least for now, because short-term fixes so far have obscured the seriousness of the risks to the region. Water is still cheap, thanks to the federal subsidies for all those dams and canals that make it seem plentiful. The myth persists that technology can always outrun nature, that the American West holds endless possibility. It may be the region's undoing.