SIERRA VISTA — Two recently released Arizona State University (ASU) studies take a hard look at the growing crises in adequate water supplies for property owners, developers and agricultural users across the state.
“The Elusive Concept of an Assured Water Supply, the Role of CAGRD and Replenishment,” focused on the Central Arizona Groundwater Replenishment District (CAGRD), brought to light the difficulties facing the Arizona Department of Water Resources (ADWR) to prove adequate water supply for 100 years.
The process is the standard for approval of underground water withdrawal permits for economic development, including agriculture, within the CAGRD, which includes the Active Management Areas (AMA) of Phoenix, Pinal, Tucson, Santa Cruz and Prescott counties.
The Kyl Center’s advisory board and staff recognized that in the wake of the historic long-awaited Drought Contingency Plan of this summer, the issue of water for growth created a focus for CAGRD. It was the catalyst for an in-depth look at the state’s water future. ASU researchers Kathleen Ferris, ASU Senior Research Fellow; Sarah Porter, executive director; and Grady Gammage Jr., a senior research fellow with the Kyl Center for Water Policy at Morrison Institute; performed the extensive study, which has already been both acclaimed and condemned.
“We are hopeful that our report will prompt a discussion about how to make the CAGRD more sustainable,” the researchers said.
In an interview with the Herald/Review, Porter said, “Our ‘Elusive Concept’ report is a little bit controversial. We have had mixed feedback — mostly positive, though — and the people who are not delighted with it have not been able to point to anything inaccurate in the report.”
According to the study, in 1993 the state “changed course” from surface water sources to “non-renewable groundwater sources” and legislators promised “groundwater would be replenished with surface water” acquired by the CAGRD. This decision came with “intended and unintended consequences for water management and urban development in Arizona.”
The study stated, “When the CAGRD was established, it was assumed there would be sufficient excess Central Arizona Project (CAP) water from the Colorado River to meet the CAGRD’s replenishment obligations through 2046. That assumption proved incorrect as enrollment radically outpaced supply and other entities with long-term CAP contracts used more and more of their rights. Further shortages of Colorado River water will reduce the amount of Central Arizona Project (CAP) water available to meet CAGRD’s replenishment obligations.”
Data used for the study to scope the possible and likely impacts were provided by experts at ADWR and the U.S. Geological Survey (USGS).
The study noted CAP is to acquire “water supplies and replenish aquifers equal to the excess quantities of groundwater used for these developments. The program has grown beyond all expectations and there’s a very real risk that the CAP will not be able to acquire the water supplies necessary to meet future replenishment obligations. Regardless, the costs of water for replenishment will steadily increase, and homeowners in CAGRD lands are vulnerable to steep replenishment assessments in the future.”
Does this apply to Cochise County? Porter said it was a “yes” and “no” answer.
“Yes, because generally growth on non-replenishing groundwater is worrisome: A declining water table presents serious consequences, like subsidence, high pumping costs, lower water quality and, as discussed in the report, communities that depend on non-replenishing groundwater eventually will need a new water supply. Where will that water come from?”
She went on to say Cochise County’s groundwater problems are a unique situation and the solutions are best developed by local stakeholders with assistance from ADWR.
“In comparison with urban development, agriculture is a big water user and does not present opportunities for reuse, so solutions are limited,” Porter said. “I need to point out that Sierra Vista has the special problem of creating a cone of depression that will draw in flows from the San Pedro. This issue is not discussed in our report.”
Porter continued, explaining the “no” part of her answer, “No, because our report focuses on a specific program that allows developers within AMAs an alternative path to ensuring that their groundwater pumping is consistent with the goal of the AMAs.”
Price of Uncertainty ReportIn a separate report, titled the “Price of Uncertainty,” Porter and Ferris delved into the quagmire that is the Gila River adjudication, probably the longest running court battle in the state as it hits its 45-year anniversary. The case has racked up some 57,000 competing water rights claims and includes over 32,000 litigants. This has created a dependency on groundwater and surface water.
For the past three years, the Kyl Center has been involved to help resolve claims in the Gila River adjudication.
“A cloud of uncertainty hangs over Arizona,” as businesses and communities have no idea where they stand in the determination of water rights and therefore have limited ways to look to the future when it comes to providing water for the needs of a growing population, according to Ferris and Porter’s report.
What makes the adjudication so complicated is three sources of water — surface, subsurface water that flows beneath a river or adjacent to a river and underground water — have been considered separate sources, not interconnected. In most of the state, groundwater pumping is unregulated outside of AMAs in rural areas, but ADWR still has to provide the 100-year water adequacy permits.
“A person may drill a well of any size and pump as much groundwater as desired without permission from the state regardless of the impacts on existing well owners,” they wrote.
However, the Arizona Supreme Court ordered ADWR to delineate a subflow zone in every river, including wells owned outside a subflow zone which could impact the rivers and streams in the Gila River adjudication. They point out the San Pedro River watershed’s subflow zone was the only study completed, though it still is being questioned. New wells drilled in targeted areas could be most affected by the adjudication.
However, Ferris and Porter emphasized, “Delineating a subflow zone only opens the door to more difficult questions yet to be answered. How much water of any particular well is pumping from the subflow zone and how much from groundwater.”
San Pedro River water claimants use 64 percent for crop irrigation and stock ponds, 29 percent for domestic use and 6 percent for other uses.
For the Verde River claims, 56 percent is for domestic uses, 42 percent for irrigation and stock ponds, with only 2 percent for other uses.
In the entire adjudication for the Gila River, 45 percent is for domestic use and 47 percent in irrigation and stock ponds, with 8 percent use for other sources. The researchers point out over 90 percent of the claims in the Gila adjudication use less than 250 acre-feet of water per year, which they say is “a relatively small claim.”
This story is the first part of a series which will detail more of the work of the Kyl Center on the water studies recently completed.