AMWUA Blog

Jan 13 2020Share

Groundwater in Arizona: Past, Present, and Future - Part One

By Warren Tenney


TerminologyThis year we celebrate the 40th Anniversary of the Groundwater Management Act. Through this three-part series on groundwater, we will look back at the past, acknowledge how far we have come, and discuss the challenges and the groundwater pumping concerns we still collectively face.


Part One-
Groundwater: What is it and Why Does it Matter?

Groundwater is one of our most valuable resources, even though you probably never see it or even realize it is there. By definition, groundwater is water that exists underground in saturated zones beneath the land surface. It is different than surface water that flows in more visible channels such as streams, rivers, reservoirs, and lakes. Currently, in Arizona, groundwater accounts for 40 percent of our total statewide water use.

Groundwater InfographicContrary to popular belief, groundwater does not form underground rivers. It fills the pores and fractures in underground materials such as sand, gravel, and other rock, much the same way that water fills a sponge. It can only be removed by pumping through wells, much like a straw in a glass.

The rock materials that allow for water to gather and be naturally stored are called aquifers. An aquifer is an underground formation of permeable rock, sand, and stones where quantities of water have gathered for thousands of years. Aquifers come in all sizes and their origin and composition are varied. They may be small or very large and can run for thousands of square miles underground all while remaining out of sight.

Groundwater is a valuable resource that is finite and once it is pumped, it is gone. While some natural groundwater replenishment may occur from precipitation, river, and lakes, the impact of those sources is minimal here in our desert climate. The majority of any replenishment that occurs in Arizona is done by storing or recharging surface water underground. This means that there is a finite supply of groundwater and depleting a key water source quicker than it can ever be replenished puts our future at risk.

Queencreek FissuresThe depletion of groundwater from over-pumping comes with additional consequences. It can trigger other major issues such as causing aquifers to shrink and dry up, hindering its capability to store water in the future as well as make it harder to extract water; the drying up of wells; reduction of water in nearby streams and rivers; and land subsidence (sinking) and cracks or fissures that can run deep and far, which can create major problems to infrastructure and properties.

Globally, groundwater is the most extracted raw material and accounts for about 30 percent of the world’s available freshwater. A recent NASA study concluded that 21 of the largest 37 aquifers in the world have exceeded sustainability tipping points and are being rapidly depleted. That is an issue that initially plagued Arizona decades ago and while we have improved our management of this resource, protecting our groundwater remains a critical priority for us.

AZsWaterSupplyChart(2015) CopyBack 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. Thus, investments were made in many urban areas in our State to enhance our water sources and diversify. Thanks to those preparations, the AMWUA cities, now have a collective water portfolio that is made up of 45 percent Colorado River Water (CAP), 41 percent Salt River Project (SRP), nine percent reclaimed water, and only five percent groundwater. Overall, we have seen a much-needed decline in the amount of groundwater pumping especially in Central and Southern Arizona.

Even though the overall usage of groundwater in Arizona has been reduced to 40 percent, groundwater is still a fundamental water source and in some areas of Arizona, it remains the only water source, highlighting the importance of managing this resource not just for today but for future generations.

For anyone to better ensure groundwater remains an available water source for when we may need it most, it is vital that we preserve as much of it for the future and continue to utilize alternative and renewable water sources, like surface water supplies that we get from CAP and SRP. We also need to continue to explore innovative ways to ensure reclaimed water is being utilized to its full potential.

We must embrace and acknowledge the fact that groundwater is fundamental to a sustainable life here in the desert, and the challenges we face are far too great to ignore. That’s why we must build upon the successes of the 1980 Groundwater Management Act to ensure it is strengthened, not weakened, and that our groundwater issues are once again addressed.


This is the first of a three-part series on groundwater as we aim to explain its importance, celebrate the accomplishments of the 1980 Groundwater Management Act and discuss growing concerns over groundwater depletion in Arizona.

Next Week: 
Part Two -
 The 1980 Groundwater Management Act: A Monumental Piece of Legislation That is Still Relevant 40 Years Later


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