Editor’s note: This analysis of the Interior Department’s Record of Decision has been posted on both the ADWR and CAP websites.

On May 9, 2024, the Department of Interior signed a new Record of Decision (ROD) to implement the Lower Basin’s commitment to conserve 3 million acre-feet to address critical elevations in Lakes Powell and Mead in the near term through 2026.  The ROD supplements the 2007 Interim Guidelines (for Lower Basin shortages and coordinated operations of Lake Powell and Lake Mead) in order to address the potential for continued low runoff conditions in the Colorado River Basin.

Why was this ROD necessary?

The Colorado River Basin relies on runoff from the snowpack in the Rocky Mountains and Upper Colorado River Basin. The Colorado River Basin has been experiencing more than two decades of drought, exacerbated by climate change. Moreover, the three-year period between 2020 through 2022 saw some lower runoff, causing historic declines in both Lake Powell and Lake Mead.

With this background, revisions to the 2007 Guidelines were necessary to protect all who depend on the Colorado River – more than 40 million people, 5.5 million acres of irrigated farmland, 30 Basin tribes, environmental resources across seven states and parts of Mexico.

What does the selected alternative propose for Lake Mead?

The selected alternative reflects commitments by water users in Arizona, California, and Nevada to conserve 3 million acre-feet in Lake Mead through 2026, the first 1.5 million of which would be completed by the end of calendar year 2024. These conservation volumes will exceed what is required under the 2007 Interim Guidelines and the Lower Basin Drought Contingency Plan. These additional volumes of conservation under the ROD could add nearly 37 feet to Lake Mead between 2023 and 2026.

In addition, if the Bureau of Reclamation (Reclamation) projects that Lake Mead could drop below elevation 1,025 feet, the Lower Basin States, within 45 calendar days, are to provide Reclamation with an implementation plan to protect Lake Mead from reaching an elevation of 1,000 feet.

What does the selected alternative propose for Lake Powell?

The selected alternative also sets forth conditions under which Lake Powell releases could be adjusted downward, mid-year, to 6 million acre-feet. If Lake Powell is operating in a mid-elevation release tier or lower elevation balancing tier, and the minimum probable scenario in the 24-Month Study shows Lake Powell dropping below elevation 3,500 feet, Powell releases could be adjusted to no less than 6 million acre-feet.

Under the selected alternative, the actions authorized under the Upper Basin Drought Contingency Plan, like the drought response releases, would continue. However, no new conservation towards the SEIS was contributed by the Upper Basin States.

Are the conservation volumes mandatory?

The 3 million acre-feet of conservation proposed by the Lower Basin States is voluntary, but made mandatory by agreements certain Lower Basin Colorado River water users have entered into with Reclamation. Conservation of up to 2.3 million acre-feet is federally compensated. The rest is either uncompensated or compensated by state or local entities. The Arizona Department of Water Resources and Central Arizona Project funded the intentionally created surplus (ICS) Preservation Program in 2023 that conserved 41,776 acre-feet of water toward the SEIS conservation.

Does the ROD protect the Colorado River system?

Yes. The process mandated by the National Environmental Policy Act that culminated in the ROD modeled the selected alternative against hydrologies drier than what was experienced in the Colorado River Basin in the past 30 years, and drier than what is forecasted under the 2024 runoff. Under this modeling analysis, the selected alternative performs well with both Lake Powell and Lake Mead projected to be above critical elevations through 2026.

Many Arizona parties have made significant contributions toward reaching the goal of 3 million acre-feet of water through 2026, conserving nearly 950,000 acre-feet in 2023 alone. Thank you to the Arizona water champions for contributing to the stability of the Colorado River system.