After considerable data analysis and review, the Arizona Department of Water Resources has completed work on its new model of groundwater conditions in the Phoenix Active Management Area (AMA), a region of south-central Arizona encompassing 5,646 square miles and, with 4.6 million residents, the most densely populated area in the state.

The results of the numerical basin-scale groundwater flow model projection show that over a period of 100 years, the Phoenix AMA will experience 4.86 million acre-feet (maf) of unmet demand for groundwater supplies, given current conditions. The term “unmet demand” refers to the amount of groundwater usage that is simulated to remain unfulfilled as a result of wells running dry in the model. To show the physical availability of groundwater under the Assured Water Supply (AWS) program, existing and assured water supplies need to be fully met.

In keeping with these findings of unmet demand, the State will not approve new determinations of Assured Water Supply within the Phoenix AMA based on groundwater supplies. Developments within existing Certificates or Designations of Assured Water Supply may continue, but communities or developers seeking new Assured Water Supply determinations will need to do so based on alternative water sources.

The constraints regarding the physical availability of groundwater are attributable to the cumulative results of decades of groundwater overdraft and the continued reliance on groundwater resources.

This Phoenix AMA model is the most comprehensive, basin-scale numerical groundwater model developed for an AMA in the state of Arizona. 

Since the implementation of Arizona's Groundwater Management Act of 1980, the objective of AMAs has remained consistent: to encourage the utilization of alternative sources for new development in order to reduce reliance on groundwater.

The new Phoenix AMA model shows that the primary goal of the 1980 Act is largely being met: existing homeowners are protected and will continue to receive their water deliveries into the future. The AWS program is working as intended – as a consumer-protection program - to ensure water supplies are available in advance of growth.