Groundwater is a valuable but limited resource

The Phoenix area’s groundwater supply entered the spotlight last year when the Arizona Department of Water Resources released its groundwater model  of the Phoenix Valley. The model projected that there will not be enough groundwater available to meet anticipated demands over the next 100 years. As a result, the construction of new subdivisions that rely on groundwater on the periphery of the Valley was halted. 

Last week, we offered insight into the new rules under consideration—the Alternative Pathway to Designation or “ADAWS” —which would allow more water providers to obtain Designations. This would reduce their reliance on groundwater and allow for sustainable growth based on the principle of water first, then development.

With so much discussion about groundwater in Arizona and the proposed new rules, many people are looking for basic information on why this water source is so important and garnering so much attention. We are here to help by providing some basic groundwater facts.

What is groundwater?

Groundwater is a crucial resource of immense value that often goes unnoticed because it is not visible like surface waters such as rivers and lakes. By definition, it is water located in saturated areas below the land surface. In other words, it’s water that is found underground. Groundwater fills the gaps and crevices in sand, gravel, and rocks like water saturating a sponge. 

The geological formations that consist of permeable rock, sand, and gravel that store and naturally accumulate water are known as aquifers. Aquifers vary greatly, from small pockets to extensive systems covering thousands of square miles and house water collected for centuries. Accessing groundwater requires pumping it through wells, like using a straw to sip from a glass.

Why is groundwater protection important?

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

ADWR’s groundwater model showed that groundwater levels are expected to drop by an average of 185 feet over 100 years in the Phoenix-wide area, compared to the 92-foot decline over the last 120 years.

Over-pumping groundwater leads to several serious consequences. It can cause aquifers to shrink and dry up, reducing their ability to store water and making extraction increasingly difficult. It can also lead to the drying of wells, land subsidence that can severely damage infrastructure and properties, water quality suffers the deeper you pump, resulting in reduced water availability in nearby streams and rivers.

What actions have been taken to protect our groundwater?

In the 1950s, approximately 70 percent of the water used in Arizona was groundwater. The realization that we have a limited supply of groundwater led to much-needed long-term planning and regulations, resulting in the signing of the 1980 Groundwater Management Act  (GMA) into law. Thus, investments were made in many urban areas in our state to enhance and diversify our water sources. 

To demonstrate a 100-year assured water supply , the AMWUA cities have invested billions in water resources and infrastructure so they do not solely rely on groundwater. Collectively, they have built 30 water treatment plants to utilize surface water supplies delivered by CAP and SRP while dramatically reducing their reliance on groundwater. Yet, it remains a crucial backup water source, especially in times of shortage of other water supplies. 

Although usage across the state has decreased to 40 percent, groundwater remains essential in Arizona, particularly in certain rural regions where it is the only water source. This underscores the necessity of managing this resource now and in the future.

Why does groundwater protection matter to the AMWUA cities?

The AMWUA cities understand that water security is the foundation of our vibrant communities. They know firsthand that our economy thrives as a direct result of providing certainty that they can meet the water needs of their residents and businesses today and in the future.  

Yet, as municipal water providers face their supply of Colorado River water significantly decreasing after 2026, they will need to offset those reductions, including utilizing water they have stored underground. This comes at the same time that the Phoenix-area aquifer is stressed and unable to support new growth that relies solely on groundwater. Therefore, the AMWUA cities know that the failure to protect the long-term health of the aquifer could jeopardize their ability to meet the demands of current residents and businesses. This is why they are so adamant about upholding the 100-year Assured Water Supply Program and only supporting new policies, such as the ADAWS rules, that sustain our local aquifer for the future.

In conclusion, all this highlights the importance of actively managing and safeguarding our groundwater. The goal is to foster responsible growth and resilience within our communities, ensuring we can thrive without over-reliance on this vital but finite resource. This proactive approach allows us to create a balanced framework that supports both current needs and the well-being of future generations.

For 55 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 .