How much Colorado River water is Arizona losing in 2027?

Arizona's apportionment falls to 2.04 million acre-feet in 2027 and 2028, a reduction of 760,000 acre-feet, the deepest cut of the three Lower Division States. California gives up 440,000 acre-feet and Nevada 50,000. The figures are in Reclamation's operating guidelines issued with the Record of Decision on August 21, 2026.

Are data centers responsible for Arizona's Colorado River cuts?

No, not at that scale. Phoenix data centers are estimated to use around 1,182 acre-feet of water a year, about 0.16% of the 760,000 acre-feet Arizona gives up, and agriculture accounts for roughly 72% of the state's water use. Data-center demand is nonetheless the fastest-growing new industrial draw, and projections cited by Grist would take it to about 1.5% of the cut.

Why did the federal government set Colorado River rules instead of the states?

The seven basin states did not reach a consensus framework, so Interior completed its own environmental review, publishing a Final Environmental Impact Statement on July 31, 2026 and a Record of Decision on August 21, 2026. Reclamation has said a seven-state agreement can still be incorporated if the states reach one.

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Arizona, the Colorado River and the data centers

The federal cut, the facility numbers, and the ratio between them · guidelines issued August 21, 2026

The Department of the Interior issued its Record of Decision on August 21, 2026, after the seven basin states did not reach a consensus framework. The Final Environmental Impact Statement published July 31, 2026. Source: Bureau of Reclamation, Colorado River Post-2026 Operations
For 2027 and 2028 the Lower Division States are apportioned 6.25 million acre-feet, a reduction of 1.25 maf. Arizona absorbs 760,000 acre-feet of that, the deepest cut of any state (247.65 billion gallons a year). Source: Bureau of Reclamation, Colorado River Guidelines for Coordinated Operations of Lake Powell and Lake Mead, Operating Years 2027 and 2028 (August 2026)
Phoenix data centers were estimated at around 385 million gallons a year, which is 1,182 acre-feet, or 0.16% of Arizona's cut. At the projected 3.8 billion gallons a year they would reach 11,662 acre-feet, or 1.5% of it. Source: Grist, citing a Ceres estimate
Agriculture accounts for about 72% of Arizona's roughly 7.0 million acre-feet of annual water use, municipal use 22% and industry 6%. Source: University of Arizona MAP Dashboard, Arizona's Water Use by Sector (citing Arizona Department of Water Resources)

Arizona is giving up more Colorado River water than any other state at the same time as it is approving data centers. Both things are true, and the question that follows is an arithmetic one that almost nobody publishes: how much of the cut is the data centers?

The cut, as the guidelines write it

State	Apportioned, 2027 and 2028	Reduction	Reduction in gallons
Arizona	2.04 maf	760,000 af	247.65 billion gallons
California	3.96 maf	440,000 af	143.37 billion gallons
Nevada	250,000 af	50,000 af	16.29 billion gallons

Of the 6.25 maf that shall be apportioned each calendar year for consumptive use in the Lower Division States of which 2.04 maf shall be apportioned for use in Arizona, 3.96 maf shall be apportioned for use in California and 250,000 acre-feet (af) shall be apportioned for use in Nevada, reflecting reductions of 760,000 af in Arizona, 440,000 af in California, and 50,000 af in Nevada

Source: Bureau of Reclamation, Colorado River Guidelines for Coordinated Operations of Lake Powell and Lake Mead, Operating Years 2027 and 2028 (August 2026)

The Record of Decision, titled Decision Framework for Colorado River Guidelines: Coordinated Operations of Lake Powell and Lake Mead (2027 to 2036), was issued on August 21, 2026 after the seven basin states did not reach a consensus framework. The Final Environmental Impact Statement published July 31, 2026.
The 2027 and 2028 guidelines are the first two-year set under that framework; Reclamation states that subsequent guidelines are expected at two-year intervals through 2036.
Beyond the 1.25 maf annual reduction, contractors in the Lower Division States are to conserve an additional 700,000 af of System Conservation water in total across 2026, 2027 and 2028 under voluntary agreements.
If a Most Probable 24-Month Study projection shows Lake Mead falling below 1,010 feet within the following twelve months, the Secretary is required to consult with the basin states and tribes on further actions.

How the data centers compare

Set the two numbers side by side. Arizona surrenders 760,000 acre-feet a year. Phoenix data centers are estimated to use 1,182 acre-feet a year today, and are projected toward 11,662 acre-feet. That is 0.16% of the cut now and 1.5% at the projection.

Both readings of that arithmetic are honest, and they point in opposite directions. Data centers are not what is draining the Colorado River: the cut is an order of magnitude larger than the entire Phoenix data-center industry, and agriculture uses about 72% of Arizona's water. But data-center demand is the fastest-growing new industrial draw in the state, it is concentrated in specific municipal systems rather than spread across the state, and unlike a farm it is an industry with a genuine choice about which state it builds in.

The projection above is the source's, not ours. This site publishes no forecasts of its own; see about and methodology.

What Arizona has actually done about it

2026-03-04 - Ceres estimated that active Phoenix data centers used around 385 million gallons of water per year as of summer 2025, with projections reaching around 3.8 billion gallons per year, which the reporting notes is less than 1 percent of Phoenix residential consumption. Source: Grist
2026-03-04 - Mesa, Avondale and Phoenix have each passed ordinances capping water use for industrial facilities and requiring developers to buy supplemental water supplies to exceed those caps. Large water users in Mesa supplied the city with roughly 7,800 acre-feet of additional water supplies. Source: Grist
2026-05-28 - The Arizona Department of Water Resources approved two commercial wells for the Project Blue data center in Pima County, carrying groundwater rights totalling 96.50 acre-feet per year. Reporting put potential facility use at up to 31 million gallons of water per year, with officials estimating 15,000 to 20,000 gallons per day in practice. The company is required to report its water use to ADWR annually. Source: AZPM
2026-03-04 - After local opposition in Tucson, the Project Blue developer committed to a zero-water cooling system, and later moved forward with similar plans in nearby Marana. Source: Grist
2026-03-04 - In Mesa, where Meta and Apple operate facilities, industrial water use accounted for around 6 percent of the city's total potable water use in 2024. Source: Grist
2026-03-04 - Arizona has blocked Buckeye and neighboring Pinal County from permitting new development that relies on groundwater, a constraint that applies to the same Phoenix-area groundwater basins where data centers are being sited. Source: Grist

The electricity side of the same bill

A data center's water shows up twice: once in its cooling and again, roughly 12 times over, at the power plants that supply it. Arizona's electricity picture, including the rate cases now before the Corporation Commission, is on the Arizona electricity page, and the water arithmetic for a given facility size is on the water hub.

Download the cuts (CSV) · Facility figures → · Arizona electricity →