The Lower Colorado River Basin entered its first-ever Tier 2a shortage in 2023. Here is what was cut, who it affects, and why deeper reductions may follow.
SouthWest Water Conservation ·
Originally reported by
Know Your Water News (Central Arizona Project)
DeEtte Person · November 30, 2022. SouthWest Water Conservation summarizes the facts below and does not republish the original article.
Read the originalThe Lower Colorado River Basin entered a Tier 2a shortage on January 1, 2023 — the first of its kind. Central Arizona Project reported the details as the reductions took effect; the figures below are theirs, and the full reporting is linked at the end.
What the reduction actually is
- For Arizona, Tier 2a represents a 592,000 acre-foot reduction to the state's Colorado River supply.
- That equals about 34% of CAP's normal supply in an average year, 21% of Arizona's Colorado River supply, and roughly 9% of Arizona's total water use.
- For CAP water users, there is no longer Colorado River water available for the Excess Water and Agricultural pools.
- Municipal and industrial supplies see a 3% reduction; tribal supplies see a 7% reduction.
Why deeper cuts may follow
Hydrologic modeling at the time indicated the basin would face deeper levels of shortage in following years. Tier 2a was certain for 2023, but stabilizing critical levels at Lake Powell and Lake Mead was expected to require more — any additional reductions would come on top of Tier 2a.
The 2007 Interim Guidelines governing coordinated operation of Lakes Powell and Mead expired at the end of 2026. The Arizona Reconsultation Committee, convened by the Arizona Department of Water Resources and CAP, was created to shape Arizona's participation in negotiating what replaces them — which is why the guidelines fight remains the single most consequential water story in the state.
One acre-foot is roughly a year's water for three Arizona families. A 592,000 acre-foot cut is not an abstraction.
Sources
Reported by Central Arizona Project. Read the originals: