BY: Warren Tenney

Colorado River Crisis Increases Importance of Managing Groundwater Supplies

Published Oct 11, 2022

As we confront a future with less Colorado River water, we are reminded about the importance of another critical water supply – groundwater. Both Colorado River water and groundwater have a long, interconnected history in Arizona, and this relationship becomes more important than ever with looming shortages. In fact, a key reason for building the Central Arizona Project (CAP) canal was to bring Colorado River water to Central and Southern Arizona so we could protect our groundwater.  

Prior to the construction of the CAP, Arizona was experiencing decades of unregulated groundwater pumping that was drying up wells, reducing water in streams and rivers, causing land subsidence, and putting landowners' and homeowners’ futures at serious risk. Seeing this groundwater depletion crisis, the federal government threatened to withhold financing for the CAP until Arizona got its water management house in order. This culmination of events led to the passage of the landmark 1980 Groundwater Management Act , including its provisions for the 100-year Assured Water Supply Program. At their core, the Groundwater Management Act and Assured Water Supply Program are designed to reign in unsustainable groundwater pumping and to ensure new growth is built upon a secure, renewable water supply.

Since the construction of the CAP was completed in 1993, the delivery of Colorado River water to Central and Southern Arizona has played a critical role in meeting these requirements, providing communities with an alternative to groundwater that has helped aquifers rebound after many decades of over-pumping. In fact, “conservation” is included in the name - Central Arizona Water Conservation District (the statutory entity that operates and maintains the CAP) as a reference to conserving groundwater through the building of the CAP.

Four decades later, it is important to remember that Colorado River water has played a critical role in preventing the further depletion of our finite groundwater supply. Now, as we face a future with less of this key water supply, it’s even more important that we protect our groundwater and hold firm to our commitment to demonstrating a 100-year water supply for new growth.

The 100-year assured water supply is the platinum standard that no other state can match. It provides consumer protection to homebuyers and ensures sustainable growth. The value and benefit of this 100-year assurance are evident in the ability of our desert communities to thrive with the immense population and economic growth we have seen over the past two decades. Specifically, new subdivisions in the Phoenix, Pinal, and Tucson areas cannot be built unless they can prove they have access to a 100-year water supply. Additionally, businesses and industries know that they can confidently make long-term investments in Arizona because of the certainty that our water management framework affords. This includes manufacturing, high-tech industry, financial services, health care, and higher education institutions collectively supporting the Phoenix metropolitan area's $281 billion GDP.

As a desert state in the Southwest, Arizona will always be questioned about having enough water. Yet, the 100-year assured water supply requirement shows that Arizona is serious about managing its water to protect residents and businesses in the Valley for the long term.

The simple principle of the Assured Water Supply Program is “water first, then development” and should be viewed as a cornerstone of Arizona's responsible water management. This principle has encouraged the sustainable use of our river and recycled water, spurred investments in infrastructure, and led to innovative ways to conserve and manage our water resources.

Each AMWUA city is proudly designated as an Assured Water Supply provider. To meet this standard, each must apply for re-designation every fifteen years, making the 100-year mark a rolling timeframe. The re-designation process ensures that their water sources will be evaluated regularly. The AMWUA members are committed to protecting the long-term sustainability promoted by the Assured Water Supply Program because they do not just plan for next year’s water needs but the next century.

Until the Colorado River is stabilized and additional supplies are developed, the uncertainty around our water will require us to make extra wise decisions, including sustaining the 100-year assured water supply requirement. All of this provides security for existing residents who rely on having dependable water sources and certainty for new families and businesses looking to invest in Arizona.

Ensuring long-term water sustainability is vital for our communities to remain resilient generation after generation. In the meantime, the Assured Water Supply Program will force Arizona to confront tough questions about growth and the willingness to develop responsibly, just as it was meant to. 

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For over 50 years, 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 .