Strategic Aquifer Protection
Actions to improve groundwater management are critical to ensure sustainable aquifers, accommodate future growth, and assure water availability during times when normal supplies are reduced.
Granite Reef Underground Storage Project
Granite Reef Underground Storage Project (GRUSP) was the first major recharge facility in Arizona. It is one of the largest of its kind in the US. It covers 217 acres and it is permitted to store 93,000 acre-feet annually.
Credit: Mark Durben
The aquifers containing groundwater beneath our feet are vital to our way of life. They supply a portion of the water we use, and they act as underground reservoirs to buffer against reduced water deliveries from the Central Arizona Project or Salt River Project. With little precipitation, these aquifers naturally replenish very slowly. Much of the water in the aquifer is “fossil water,” trapped underground eons ago. It is not a renewable supply. Therefore, we must carefully manage these aquifers.
In recognition of this, Arizona’s 1980 Groundwater Management Act requires that in the most populous areas of the state, the water withdrawn from an aquifer be replaced with an equivalent amount of renewable water. The law includes a system of credit accounting whereby users can pump groundwater in one location in exchange for water that was artificially recharged or stored in another location. As progressive and beneficial as the system is, its flexibility ignores the fact that water flows very slowly both horizontally and vertically between aquifers. In other words, the aquifer system is not one giant bathtub.
This physical separation of storage and recovery, if managed improperly, can lead to areas of localized groundwater depletion. Decreasing groundwater levels can cause irreversible land subsidence that cracks foundations, creates sinkholes, and damages critical infrastructure. Once subsidence occurs, the aquifer can never hold as much groundwater again; like a dried sponge that does not expand when rewetted. Once the water is gone, it is gone. Further, depleted aquifers mean there is less of a buffer to help us avoid the effects of shortages in our surface water supplies.
This disconnect between storage and recovery is one example of the many complex challenges to sustainable aquifer management. AMWUA believes the aquifers serving its members are generally in good health but they could be improved to better prepare for population growth and pending surface water shortages and to ensure their long-term sustainability.
Drone Image of Fissure, Pinal County
Fissures are associated with land subsidence that accompanies extensive groundwater mining, and they are fairly common in central Arizona. This example, discovered by the Arizona Geological Survey, is the largest single fissure in the state, measuring two miles in length, ten feet wide, and 27 feet deep. Credit: Brian Gootee, AZGS
To begin addressing aquifer health issues, AMWUA created the Strategic Aquifer Protection (SAP) concept. AMWUA uses the concept to describe diverse efforts to improve aquifer health within the Phoenix Active Management Area (AMA), an area of consistent groundwater regulation roughly encompassing the Phoenix metropolitan area. SAP was born out of an earlier effort led by the Arizona Department of Water Resources (ADWR), but it is distinct in its ideas and approach. SAP is an ongoing, long-term effort to improve aquifer health. SAP efforts include:
- Updating water recharge rules to remove barriers to storing more water in the ground;
- Providing additional incentive or regulation to link where water is stored to where it is recovered; and
- Protecting investments in aquifer health from the unrestrained movement of groundwater pumping rights from one location to another.
To advance the Strategic Aquifer Protection concept, AMWUA members have been meeting to identify areas where the current regulatory environment could be improved to promote more sustainable aquifer management. AMWUA has been meeting with staff at the Arizona Department of Water Resources to discuss potential strategies. Once initial concepts are identified, AMWUA will work with interested parties to vet and strengthen the concepts and gain support for the final proposals that emerge from the process. AMWUA members also are examining their own operations to determine if any voluntary improvements can be made.
Aquifer Storage and Recovery Well
The City of Phoenix operates this Aquifer Storage and Recovery (ASR) well at its Cave Creek Water Reclamation Plant. These wells inject potable water directly into underground aquifers to both improve local groundwater conditions and as a supply for future use. Credit: Brett Fleck
What You Can Do
Investigate groundwater conditions where you live and ask your water provider what it is doing to maintain and improve the health of the aquifers beneath your home.