Nov 21 2023Share

Don’t Mortgage Our Future by Weakening Assured Water Supply Requirements

By Warren Tenney

Arizona is confronting water challenges but now is not the time to undermine the 100-year Assured Water Supply Program that has allowed our communities and economy to thrive here in the desert. As many in Arizona’s water community are striving to develop more ways to prudently plan, manage, and invest in our water resources and infrastructure, it is disheartening to have the State Senate President suggest that Arizona’s 100-year assured water supply requirement is too hard and should be weakened or even removed. 

Senate President Warren Petersen recently criticized the findings of the Arizona Department of Water Resources (ADWR) groundwater model for the Phoenix metropolitan area showing that in 100 years that there would be a 4% shortfall in groundwater supplies to meet anticipated demand. This has halted residential development on the outer fringes of the Phoenix area because ADWR is now legally required to stop issuing determinations of a 100-year supply if developments are supplied only by groundwater. 

Yes, this pause on development is unfortunate for the homebuilding industry on the Valley’s far west and east sides. Yes, the groundwater model’s results, along with uncertainty surrounding the Colorado River and groundwater depletion in rural Arizona, have led some media to foolishly claim Arizona is running out of water. Yet, this is the exact moment we need state leaders to set the record straight about Arizona’s water situation and advance solutions to better secure our future. 

Here are seven facts that need to be understood and touted as we tackle  our water challenges:

First and foremost, water providers with a 100-year Assured Water Supply designation are still open for business. The model’s findings re-emphasize the importance of developing in communities with a 100-year Assured Water Supply. These communities, including the ten AMWUA cities, have diverse water portfolios that ADWR has determined will meet the demands of current residents and future development – residential, commercial, or industrial – over the next 100 years. The ten AMWUA municipalities, which provide water to over half of Arizona’s population, are proud of their ability to provide such certainty to their residents and businesses, something cities elsewhere in the United States are not required to do. 

Second, arbitrarily reducing or removing the 100-year Assured Water Supply requirement would undermine the economic achievements of the AMWUA cities and other designated municipal water providers and signal that Arizona is not serious about addressing its water supply challenges. The economic viability of this Valley is directly linked to the 100-year assured water supply designation of the AMWUA cities. Designated water providers have demonstrated an assured water supply for their communities by investing billions of dollars in renewable water resources and infrastructure. Collectively, the AMWUA cities have built 30 water treatment plants to fully utilize surface water supplies delivered by the Central Arizona and Salt River projects and minimize their use of groundwater. These significant investments, combined with long-term planning and a culture of conservation, have positioned the AMWUA cities and other designated water providers to be resilient and show the rest of the nation the economic reliability of our communities. Lessening or abandoning the 100-year assured water supply requirement would certainly declare that Arizona is not serious about addressing its water challenges. We need our leaders to show our residents and the rest of the nation that short-term profits are not more important in Arizona than consumer protection and wisely managing water for our long-term economic success.

Third, it is misleading to link the halt of development on the fringes with the amount of available housing in the Valley. The reality is that land for wise development is still available in areas with ample water supplies. When the Phoenix area groundwater model was released this summer, an estimated 185,350 acres of developable land remains available within the ten AMWUA cities, equating to at least half a million single-family residences. This does not consider other housing development opportunities besides single-family homes or the opportunities available within other communities with designated water providers. Housing and water are each complex issues, but we must continue prioritizing consumer protection and sound water management, which have been critical in building sustainable communities with reliable and diverse water supplies since the 1980s, distinguishing Arizona as a secure place for continued investment. 

Fourth, it would be irresponsible to ignore the findings of the ADWR groundwater model. ADWR used state-of-the-art technology for the model, which was reviewed by outside hydrologic experts. The 4% shortfall in 100 years in the Phoenix area’s groundwater, which equates to 4.9 million acre-feet, also means that in 100 years, groundwater levels will drop an average of 185 feet and a 30% loss in available groundwater supplies. This will be twice of what we have seen in the previous century. ADWR has demonstrated that altering assumptions in the model does not change the declining trajectory of our aquifers. Haphazardly downgrading or negating the 100-year assured water supply requirement will only lead to increased pumping of our finite groundwater and negative consequences, such as land subsidence, that would be an outcome of declining aquifers. 

Fifth, shortfalls in our groundwater supplies will not be victimless crimes. A shortfall means our groundwater is over-allocated and that some citizens and entities will not get the water they have counted on. A shortfall will impact the assured water supplies of those who made the financial investments to qualify for a 100-year Assured Water Supply and instead will benefit those who fail to meet the 100-year standard. This outcome is not only dangerous but also unfair.

Sixth, Arizona’s water experts, through the Governor’s Water Policy Council, have developed a framework that would enable growth to start again on the edges of the Valley without weakening the fundamentals of the Assured Water Supply Program. The details of this proposal, which would provide an alternative path to an Assured Water Supply designation for undesignated water providers, will be further developed in a stakeholder process led by ADWR. The proposal seeks to ensure that growth can continue in those communities that are willing to invest in water supplies and infrastructure needed to make alternative water supplies available for their customers.

Finally, we need our elected officials to advocate what state and municipal water managers understand – securing our water future is an endless effort that requires tough work and financial investment. Our economic success has always been directly linked to how well we plan, manage, and invest in our water resources and infrastructure. New water supplies are essential for backfilling future reductions to Colorado River water as well as for new development. Developing new supplies and infrastructure requires longstanding vigilance. The Central Arizona Project took over 50 years to build from concept to flowing water. State leaders, including Senate President Petersen, must build upon last year’s historic and significant $1.4 billion commitment to the Water Infrastructure Finance Authority (WIFA) by finding ways to invest in Advanced Water Purification, the expansion of Bartlett Dam on the Verde River, and other creative long-term augmentation opportunities. None of it will be cheap. Yet, investment in water supplies and infrastructure always brings an even greater return. 

To print or save this week's blog, a PDF version is available HERE.

For over 50 years, the Arizona Municipal Water Users Association has worked to protect our member cities' ability to provide assured, safe, and sustainable water supplies to their communities. For more water information, visit

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