Now is the Time to Consider Replenishing Aquifers in Areas of Hydrologic Impact

Tom Buschatzke, Water Advisor for City of Phoenix, contributed this Guest View. He can be reached at: tom.buschatzke@phoenix.gov

Central Arizona has a tremendous asset in its extensive groundwater aquifers. The Groundwater Management Act of 1980 recognized this fact and created a framework for moving aquifer management in Active Management Areas toward sustainability. Programs such as mandatory water conservation, assured and adequate water supply requirements for municipal water providers, and underground storage and replenishment have positioned the State of Arizona as a leader in aquifer management and increased the level of certainty that water supplies will be available for existing populations, and for growth now and in the foreseeable future.

However, much has changed since the inception of the GMA and the work of water managers to achieve long-term water supply sustainability is not done. One particular issue that needs further dialogue is where replenishment of mined groundwater should take place, i.e., "replenishment within the area of hydrologic impact."

The use of mined groundwater by municipal water providers within AMAs that have a goal of safe yield is essentially prohibited. However, mined groundwater can be used as long as it is replaced, or "replenished" within an AMA. Currently that replenishment may legally occur anywhere within an AMA. To date this policy has served the state well, but factors that were not in play at the time of the passage of the GMA have arisen that call for a reexamination of this policy.

The water resources management landscape has changed significantly since the inception of the GMA in 1980. Some of those changes include: (1) accelerated growth in areas that have little or no access to surface water supplies or Colorado River water, aided by the state's creation of the Central Arizona Groundwater Replenishment District; (2) areas that have renewable supplies are experiencing growth at rates that may require acquisition of additional renewable supplies or the increasing use of aquifers, with replenishment of mined groundwater; (3) tree-ring research has come to light that shows pre-historic droughts of two to three times greater duration on both the Colorado River and within the state and a greater correlation for periods of simultaneous drought between the Colorado River and in-state streams; (4) population growth rates have far exceeded projections; (5) growth has proceeded toward the margins of the groundwater basins in areas where aquifers contain less water in storage and where detrimental impacts of aquifer dewatering such as earth fissuring are more likely to occur; (6) environmental impacts of water use have become "a part of doing business"; (7) climate change models have raised the specter of reduced Colorado River and in-state stream flows and reduced natural recharge to aquifers; (8) significant quantities of water have been stored underground for recovery at a later date for a variety of purposes that include drought protection, Indian water rights settlements and use by the State of Nevada. In summary, aquifers have evolved beyond being simply a source of water into a resource that is used to conjunctively manage renewable water supplies and groundwater resources.

All these factors add up to one indisputable truth: reliance upon groundwater aquifers to manage water supplies in the AMAs will increase over time. Aquifers will not simply sit there, untapped, for use in drought or as a hedge against future uncertain conditions. The disconnect between where water is pumped and where that water is replenished, must be addressed.

It is inevitable that groundwater recharge and pumping to utilize the water storage capabilities that aquifers provide will increase over time. It is incumbent upon prudent water managers and the State of Arizona to address the issue of replenishing aquifers in areas where the water is actually withdrawn, i.e., the "area of hydrologic impact." This issue was most recently debated on a large scale by the Governors Water Management Commission in 2000. Despite the inability of that process to resolve the issue, it has not gone away. The issue has been raised recently in smaller forums including the Arizona Department of Water Resources well rules stakeholder process and the Central Arizona Project's Strategic Plan.

This issue is not restricted to a specific sector of water providers. Rather, it will impact all water users that rely on the same aquifer to manage their water supplies. In some cases the facts will likely show that local groundwater level declines are occurring to a degree that replenishment within the area of hydrologic impact is a necessity, while in other situations that may not be the case. A concentrated effort to examine local impacts is needed and a dialogue among water users that rely on aquifers must follow. Equity for those who have invested and relied upon the current system for replenishment will be a huge issue, as will the need to maximize the use of future supplies, such as reclaimed water in a cost effective manner.

The task will not be easy and will likely move at the glacial pace that traditionally accompanies informed decision making in the complex world of water policy. The clock is ticking and the time to get the water resources community back to the table to discuss this issue is now!

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