Arizona is not currently “running out” of water in a sudden, catastrophic sense, but its long-term supply is under intense pressure from a two-decade-long drought affecting the American Southwest. The state’s water challenge involves a delicate balance between surface water imported from a severely depleted river system and non-renewable groundwater reserves. This dual strain is characterized by federally mandated reductions in surface water, while groundwater is being drawn down faster than it can naturally replenish. This situation demands unprecedented conservation and policy action.
The Dual Sources of Arizona’s Water Supply
Arizona’s water portfolio relies primarily on surface water and groundwater, supplemented by reclaimed water and in-state rivers like the Salt and Verde. The state depends on the Colorado River for approximately 36 to 38% of its total water use, delivered via the Central Arizona Project (CAP) system. Groundwater is the other primary supply, accounting for about 41% of usage, stored in underground aquifers that are often non-renewable resources.
When groundwater is pumped faster than it can be naturally recharged, a condition known as overdraft occurs, causing water tables to drop significantly. This heavy reliance on both the distant Colorado River and diminishing groundwater creates a strategic vulnerability, as reduced surface water supplies accelerate the depletion of underground storage.
The Immediate Crisis Reservoir Levels and Mandatory Curtailment
The most visible manifestation of the water crisis is the historically low level of Lake Mead and Lake Powell, the primary reservoirs for the Lower Colorado River Basin. Persistent drought and over-allocation have caused Lake Mead to drop to elevations that trigger federally mandated supply reductions. When water levels fall below 1,075 feet, the U.S. Bureau of Reclamation declares a “Tier 1 Shortage,” triggering mandatory curtailments. Due to its junior water rights, Arizona is the first state to absorb the most substantial reductions. These cuts, declared for multiple years, have reduced Arizona’s Colorado River allocation by hundreds of thousands of acre-feet annually.
Nearly all of this initial reduction is borne by agricultural users who receive water through the Central Arizona Project, particularly in Pinal County. Mandatory curtailments have forced farmers to fallow fields or invest in drilling deeper wells to access groundwater. The loss of CAP water shifts the strain directly onto the already over-stressed aquifers.
Arizona’s Internal Water Management and Conservation Efforts
Arizona enacted the 1980 Groundwater Management Act (GMA) to address unsustainable water usage and control severe overdraft. The GMA established Active Management Areas (AMAs) in populated regions like Phoenix and Tucson, covering over 75% of the state’s population. Within AMAs, the law enforces mandatory conservation requirements across municipal, industrial, and agricultural sectors. A cornerstone of the GMA is the Assured Water Supply Program, which requires developers to demonstrate a water supply available for at least 100 years. This policy links urban growth directly to sustainable water availability, prioritizing renewable sources.
Major metropolitan areas have developed extensive programs focused on water reuse and underground storage, using recharged Colorado River water and treated wastewater (effluent). This innovation creates a “water bank,” allowing cities to store surplus surface water in aquifers during wet years and withdraw it during drought years. Despite these protections, the vast majority of the state remains outside the AMAs, where unregulated groundwater use has led to severe aquifer declines in rural areas.