45 years of the Arizona Groundwater Management Act

The Arizona Groundwater Management Act of 1980 was regarded at the time as a groundbreaking legal instrument addressing the groundwater overdraft problem in heavily populated areas of the state. The Act includes several progressive provisions for managing groundwater such as establishing the Arizona Department of Water Resources, designating Active Management Areas, ensuring a 100-year water supply for new developments and implementing mandatory conservation requirements across various sectors.

The Act’s primary goal is to achieve safe-yield – a long-term balance between the annual amount of groundwater withdrawn and the annual amount of natural and artificial recharge – in Active Management Areas, thereby ending groundwater overdraft by January 1, 2025. However, as of now, this ambition remains unmet.

The Colorado River and groundwater supply more than three-quarters of Arizona’s water. The Colorado River Interim Guidelines of 2007 and the Drought Contingency Plan of 2019, which were prepared to manage the declining water levels in Lake Mead and Lake Powell, are set to expire in 2026. 

The Colorado River Basin states are engaged in negotiations to finalize new operational guidelines for the river system beyond 2026. Hence, the remaining months of 2025 and the entirety of 2026 will be crucial for shaping the future of water not only in Arizona but also in the Southwest.

Considering the importance and urgency of the issue, the major provisions of the Act and analysis of the reasons for not achieving the management goal of safe-yield are described here, alongside suggestions for groundwater management post-2025.

The Arizona Groundwater Management Act and its provisions

The Groundwater Management Act (GMA) has brought about several positive changes, one of which is the establishment of the Arizona Department of Water Resources (ADWR). The agency serves as the administrator of all state water laws except those related to water quality, which are addressed by the Arizona Department of Environmental Quality.

Originally, the most populated areas in Arizona that are heavily reliant on groundwater were designated as Active Management Areas (AMAs). Initially, four AMAs – Prescott, Phoenix, Pinal and Tucson – were formed in 1980 under the GMA. In 1995, the Santa Cruz AMA was created by splitting it from the Tucson AMA. The Douglas AMA was established in southeastern Arizona in 2022. More recently, the Willcox Groundwater Basin has been designated as the seventh AMA of the state.

AMAs are subject to the highest degree of groundwater regulation in Arizona, including prohibiting expansion of agricultural irrigation acres, mandatory water conservation programs and annual water use reporting requirements. Groundwater use within each jurisdiction is regulated by formulating groundwater management plans specific to each AMA. Phoenix, Pinal, Prescott and Tucson AMAs have each adopted five management plans, while Santa Cruz AMA has adopted three. The Douglas AMA recently adopted its first management plan.

In addition to AMAs, the GMA facilitated the establishment of Douglas and Joseph City Irrigation Non-expansion Areas (INAs) to preserve the irrigation of cultivated lands. Recently, the Douglas INA transitioned to AMA status. Additional INAs, such as Harquahala and Hualapai Valley, were respectively established in 1982 and 2022. While the level of regulation in INAs is less stringent than in AMAs, these regions remain vital to groundwater management efforts.

The Assured and Adequate Water Supply Programs (AAWSP) are other flagship initiatives administered by ADWR. Within the AMAs, the AAWSP requires developers of new subdivisions to demonstrate to ADWR a 100-year assured water supply before obtaining plat approval or selling lots. 

Outside the AMAs, the AAWSP requires developers to either demonstrate an adequate water supply or disclose an inadequate water supply to potential buyers prior to sale. These programs aim to protect consumers by ensuring a sustainable water supply for new housing developments.

The challenges of safe yield

Management goals differ across the AMAs. The Prescott, Phoenix and Tucson AMAs aimed to achieve safe-yield by January 1, 2025. Despite progress in improving groundwater management, achieving and maintaining safe-yield remains a formidable challenge.

Several challenges have hindered the state from achieving the goal of safe-yield. One of the biggest challenges is the long-term, largely uncontrolled rights to pump groundwater. Under the GMA, farmers who owned land legally irrigated with groundwater within the five years prior to January 1, 1980 were granted irrigation grandfathered rights. This allows them to continue pumping groundwater for agricultural use.

Similarly, water users with Type 2 non-irrigation grandfathered rights are permitted to withdraw historically pumped amounts of groundwater. In addition, cities, towns and private water companies have been granted service area rights, enabling them to continue pumping groundwater within their designated areas. 

These residual users are not required to offset their groundwater use with renewable supplies or replenish what they extract. Collectively, these practices have become a major barrier to achieving the GMA’s goal of safe-yield.

The Colorado River water is a major source of water for the state which currently relieves groundwater pumping pressures. However, the Colorado River Basin recently experienced the most severe drought in over a century of continuous record keeping. 

In addition, the basin is increasingly affected by the impacts of climate change. A critical concern is the early snowmelt – once a vital water source for the Colorado River – driven by warming temperatures. In Arizona, storm systems that previously brought rainfall are now shifting northward to higher latitudes.

Consequently, the state is experiencing hotter conditions, less predictable and reduced precipitation and more frequent extreme weather events. Rising temperatures also accelerate the evaporation of water stored in reservoirs, exacerbating water scarcity. Furthermore, intense summer heat increases water demand for households and agriculture.

The reduced water supply in the Central Arizona Project canal from the Colorado River forces AMAs to explore alternative sources to meet the increasing water demand of their residents. Groundwater pumping has become a last-resort solution to cope with these growing demands. This practice of increasing groundwater pumping will make the goal of achieving safe-yield even more challenging.

Recommendations moving forward

There are many actions that can be taken to prepare for this future. Here are some suggestions for consideration while amending the GMA and developing strategies to address Arizona’s water scarcity challenge:

Increase clarity on safe-yield: Safe-yield remains an aspirational goal rather than an enforceable mandate within the GMA. While it is defined as achieving a long-term balance between groundwater withdrawals and recharge, practical implementation has proven to be a daunting task due to the complexities of measuring recharge and withdrawals across diverse subbasins. Establishing a clearer, enforceable definition and pathway for achieving safe-yield is essential for meaningful progress.

Reform grandfathered rights and address unrestricted pumping: Unrestricted groundwater pumping through grandfathered rights remains a significant challenge to achieving the safe-yield goal. These rights should be reviewed, and phased limitations introduced. Where feasible, industrial sectors not served by municipal providers should be required to transition to renewable supplies or replenish groundwater use.

Promote urban development growth on former agricultural lands: Encourage urban expansion on land previously used for agriculture, particularly those near existing renewable water infrastructure. Redirecting new developments to areas already supported by municipal water systems with access to surface water or reclaimed water can alleviate pressure on groundwater supplies.

Invest in infrastructure for alternative water supplies: Strong political will and regulatory support are needed to invest in infrastructure for collecting, treating and distributing alternative water sources such as stormwater, reclaimed water and desalinated water. These systems are vital for reducing reliance on shrinking groundwater reserves and protecting aquifers for future generations.

While the GMA has been instrumental in regulating groundwater use and promoting conservation in Arizona, additional measures are imperative to meet the growing water demands of an expanding population.

Today, with vastly improved scientific tools, data and emerging technologies such as AI, future water allocation decisions must be grounded in sound science. Universities and initiatives like ASU’s Arizona Water Innovation Initiative play a vital role in this process by offering innovative, science-driven solutions that inform both state-level groundwater management strategies and the complex negotiations surrounding the Colorado River’s future.

About the author: Jagadish Parajuli is a Postdoctoral Research Scholar at the Arizona Water Innovation Initiative.