Two record lows, one 1.25-million-acre-foot bill, and Arizona pays 61 percent of it

Run the arithmetic on Interior's own percentage and the shape of the fight shows up. A reduction of 1.25 million acre-feet described as about 21 percent of Lower Basin use implies a baseline near 5.95 million acre-feet ^[4][5][1]. Measured against that baseline, the 3 million acre-foot figure carried in the final environmental impact statement is close to half of everything the three Lower Basin states take ^[11][2], and 2.4 times what Interior actually ordered ^[5]. Inside the ordered cut, Arizona carries 61 percent of the volume, California 35 and Nevada 4 ^[3]. Arizona, which faced the most severe reductions in the FEIS ^[13], called parts of the proposal unacceptable and told Interior that such cuts would devastate its water users and its economy ^[12].

The baseline itself is the part no state gets to negotiate. Douglas Kenney of the University of Colorado Boulder told Eos that flows so far in the 21st century are 20 percent below the 20th century, and that warming over the past 30 years has changed virtually every aspect of the water cycle in ways that lower streamflows ^[14]. Mead is at 27 percent of capacity and Powell at 21 ^[15][16]. Overallocation is only one reason for the gap; reduced snowpack and higher evaporation are doing their share ^[24].

How these numbers were set tells you what the post-2028 round will look like. The January 2026 draft came out of roughly two and a half years of negotiation between the Bureau of Reclamation and the seven basin states ^[17]. The public got 45 days and filed more than 18,000 submissions, most of them form letters ^[19], answered in a 54-page document ^[20]. Secretary Doug Burgum's statement credited the seven states, the 30 basin tribes, Mexico and other stakeholders for the feedback and the voluntary arrangements needed to build the 2027-2028 operating guidelines ^[21]. Voluntary is doing a lot of work in that sentence: an arrangement that was offered can also be withdrawn. Eos dates the final EIS to late July 2026 in one passage and to August in another ^[18], so the published sequence is less settled than the volumes are.

John Berggren of Western Resource Advocates, who says the decision puts the basin on the right path without making its management sustainable or resilient ^[22], set the ceiling plainly: the best case is that in two years the basin is "just barely hanging on by a thread, and very vulnerable to one more bad year that could completely tank the system" ^[23]. That is two years of settled volumes for 40 million people and 30 tribes ^[3], followed by the same argument over a smaller river.