But the river has been overdrawn for more than a century. As demand continues to grow, rising temperatures and lower precipitation caused by the climate crisis are taking an increasingly larger share of declining supplies, a trend only expected to worsen as the world warms.

Up to 4m acre-feet of cuts are needed to bring the basin back into balance – an amount equal to more than a quarter of its annual average flow. One acre-foot, a unit denoting the amount of water that can cover a football field one foot deep, is equal to roughly 326,000 gallons – enough to supply roughly three families for a year.

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“There needs to be unbelievably harsh, unprecedented cuts” that will affect water users in major ways, said Dr Brad Udall, senior water and climate research scientist at Colorado State University’s Colorado Water Center. “Mother Nature is not going to bail us out.”

The collapse of the arid western US thus begins…