Groundwater is a limited resource essential for our water security

This year marks 45 years since the passage of the 1980 Groundwater Management Act, a crucial piece of legislation that established guidelines for sustainable groundwater use in Arizona. With water security in focus, it is essential to understand why this resource has been receiving so much attention lately.

Here are the key facts you should know about Arizona’s groundwater.

What is groundwater?

Groundwater is a valuable water resource that often goes unnoticed because it is not visible like surface waters, such as rivers and lakes. By definition, it is water found in saturated zones beneath the land surface. In other words, it is water that exists underground. Groundwater fills the spaces and cracks in sand, gravel, and rocks much like water soaking into a sponge.

Aquifers are geological formations made of permeable rock, sand, and gravel that store and naturally hold water. They vary greatly, from small pockets to large systems covering thousands of square miles, with water accumulated over hundreds of years. Accessing groundwater involves pumping it from wells, similar to sipping from a glass with a straw.

Why is groundwater protection important?

Groundwater is a valuable but limited resource; it can only be used once. While natural replenishment from precipitation, rivers, and lakes does occur, its impact is minimal. The Phoenix and Tucson aquifers have benefited from water providers storing surface water underground, yet our groundwater remains a finite resource.

ADWR’s 2023 groundwater model indicated that groundwater levels are expected to decline by an average of 185 feet over 100 years across the Phoenix area, compared to a 92-foot decline over the past 120 years.

Over-pumping groundwater causes several serious problems. It can lead to aquifers shrinking and drying up, reducing their capacity to store water and making extraction more difficult. It can also cause wells to dry up, land subsidence that can severely damage infrastructure and property, and deterioration of water quality as pumping depths increase, resulting in less water available in nearby streams and rivers.  

What actions have been taken to protect our groundwater?

In the 1950s, about 70 percent of Arizona's water use came from groundwater. Recognizing that groundwater is a limited resource prompted long-term planning and new regulations, culminating in the 1980 Groundwater Management Act (GMA) . Consequently, investments were made in many urban areas across the state to improve and diversify water sources.

To ensure a 100-year water supply, the AMWUA cities have invested billions in water resources and infrastructure so they are not solely dependent on groundwater. Together, they have built 30 water treatment plants to use surface water supplied by the Central Arizona Project (CAP) and the Salt River Project (SRP), greatly reducing reliance on groundwater. However, it still serves as a crucial backup, especially during shortages of other water sources, such as the reductions in the Colorado River expected to start in 2027.

Although statewide groundwater use has dropped to 40 percent, groundwater remains vital in Arizona, particularly in some rural regions where it is the only water source. This underscores the importance of responsible management of this resource now and into the future. 

Why does groundwater protection matter to the AMWUA cities?

The AMWUA cities understand that water security is the foundation of our thriving communities. They know firsthand that our economy depends on the certainty that they can meet the water needs of residents and businesses both now and in the future.

As municipal water providers face a significant decrease in their Colorado River water supply, they will need to make up for these reductions, including drawing groundwater from aquifers. This occurs at a time when the Phoenix-area aquifer is under stress and cannot support new growth relying solely on groundwater. Therefore, the AMWUA cities recognize that failing to protect the aquifer's long-term health could threaten their ability to serve current residents and businesses. That’s why they are committed to upholding the 100-year Assured Water Supply Program and supporting policies, such as the ADAWS rules, that ensure the sustainability of our local aquifer for the future.

In conclusion, these facts about Arizona’s groundwater supply and challenges highlight the importance of actively managing and safeguarding this water. The goal is to promote responsible growth and resilience within our communities, ensuring we can thrive without over-reliance on this vital yet limited resource. This proactive approach helps us develop a balanced framework that meets both present needs and those of future generations.

For 56 years, the Arizona Municipal Water Users Association has helped protect our member cities' ability to provide their communities with assured, safe, and sustainable water supplies. For more information, visit www.amwua.org .