The Lower Colorado River Basin will be in the first-ever Tier 2a shortage beginning Jan. 1, 2023. Here’s what you need to know:

• For Arizona, a Tier 2a shortage represents a 592,000 acre-foot reduction to the state’s Colorado River supply. This equates to 34% of Central Arizona Project’s normal supply in an average year, 21% of Arizona’s Colorado River supply and about 9% of Arizona’s total water use.
• For CAP water users, this means there is no longer Colorado River water available for the Excess Water and Agricultural pools. The Tier 2a shortage will mean a 3% reduction to Municipal & Industrial supplies and a 7% reduction to Tribal supplies. See our infographic below for a graphical representation of the effect on CAP supplies.
• Current hydrologic modeling indicates the Colorado River Basin will be in deeper levels of shortage in the coming years.

The Tier 2a shortage is certain for 2023. But more will need to be done to stabilize critical levels at the Colorado River Basin’s two main reservoirs – Lake Powell and Lake Mead. The Bureau of Reclamation is considering additional protection measures, which have yet to be announced. Any additional reductions would be on top of the Tier 2a shortage.

Stay up to date by frequently visiting the River Updates section on Know Your Water News. This includes our updated Shortage FAQ and a new fact sheet on Shortage Milestones that will give you more background on the Law of the River components that have led us to this point.