More Elusive Than Ever: Arizona's Assured Water Supply Protections Under Colorado River Shortages and Groundwater Scarcity

Arizona law requires a 100-year assured water supply before selling subdivision lots - an effort to safeguard limited groundwater. For years, developers have relied on the Central Arizona Groundwater Replenishment District (CAGRD) to meet this requirement by replenishing groundwater with Colorado River water. But as river supplies shrink and replenishment demands grow, that system is faltering.Our new report, More Elusive Than Ever, examines the cracks in Arizona's current approach and the urgent need for reform.

May 2, 2025

In the state's most urban areas, Arizona's Groundwater Management Act prohibits the sale of subdivision lots that lack a 100-year assured water supply. Allowing groundwater to qualify as an assured supply conflicts with the Act's overall goal of preventing the further depletion of this non-renewing resource. For over three decades, developers and water providers in central Arizona have relied on a work-around to this dilemma allowing them to join the Central Arizona Groundwater Replenishment District, aka CAGRD, which is required to secure surface water supplies to replenish the groundwater pumped by its members.

CAGRD's 2025 Plan of Operation projects that its replenishment obligations will more than double by 2044. But with central Arizona now facing potentially dramatic shortages of Colorado River supplies -- the main source of CAGRD's replenishment water in the past -- the Director of the Arizona Department of Water Resources has informed CAGRD that it may no longer rely on most of the Colorado River water in its current portfolio. Given the conflicts between past policies and current realities, it is clear that something will have to change.

Building upon The Elusive Concept of an Assured Water Supply: the Role of CAGRD and Replenishment, our new report digs into why an assured water supply is More Elusive Than Ever.

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