Imperial Dam, Where 3.1 million acre-feet of Colorado River water is diverted annually to the Imperial Valley Irrigation District in Winterhaven, Calif.It seemed inevitable that the dwindling Colorado River would be divvied up by the federal Bureau of Reclamation. On June 14, BuRec gave the seven states in the Colorado River compact just 60 days to find a way to cut their total water usage by up to 4 million acre-feet. No plans emerged.
That concession meant the 1.4 million acre-feet capacity of the Central Arizona Project has junior water rights. In a shortage — like now — the Central Arizona Project, except for tribal water rights, could be cut to zero, a blow to cities and agriculture. For the Upper Basin states, says University of Wyoming Law professor Jason Robison, “It’s more nuanced. But there’s significant federal authority to run those Upper Basin reservoirs,” though none are very large. Where might other water cuts be found? Colorado’s 1876 constitution ranked municipal water over agriculture, making it tough to dry up cities like Colorado Springs or Aurora, even though their water rights are junior.
What the federal government can’t touch for now is any Upper Basin irrigation project created before the signing of the Colorado River Compact in 1922. In Colorado, a spreadsheet compiled by the state’s Division of Water Resources tells what projects, by date, risk losing water. Some Western slope irrigators are vulnerable because the water rights they’re using were bought by municipalities only recently, intending them for future growth.