by Blake Herzog
A task force studying the availability of groundwater in Pinal County has turned the findings of a 14-month study into the Arizona Department of Water Resources (ADWR) with hopes of resolving some issues regarding new water permits in the county, but a larger water shortage looms.
Pinal County Supervisor Steve Miller, chairman of the task force, said the group pooled their resources to hire Matrix New World Engineering’s Phoenix office to investigate the projections that went into ADWR’s 2019 pronouncement the groundwater table beneath most of the county would fall short by 10%, or 8.1 million acre-feet, of meeting projected demand over the next 100 years.
Out of that shortfall, about 2 million acre-feet was tied to residential development, 5 million acre-feet to agriculture and the rest to other uses.
When looking at the residential use category, Miller said, “the assumptions the state was using, we felt, were not a true picture of the Pinal AMA basin. So (the engineers) really just dived down into it and worked on all the assumptions the state uses, and they came up with proof that the assumptions they were using were not accurate,” he said.
“It proved that we’re about 10,000 acre-feet short over 100 years, which is almost a rounding error. We have 100 years to fix that 10,000-acre-foot problem.”
Miller emphasized that this figure applies to certificates of assured water supply already issued for homes built or planned in Pinal County, not to any additional development.
He gave as an example of faulty logic used by ADWR an assumption that when a well a water provider was using dried up, the well would not be either dug deeper into the ground or relocated.
The findings were submitted to the state this spring.
Miller said, “First, we want to know if they’re going to use our modeling assumptions in our process. And I got a feeling they might use some; I guarantee you they won’t use all of them, but we’ll see where it falls.
“The second challenge we have is, how are we going to move forward with new certificates? And we think this is going to be more of a statewide methodology,” he said.
Arizona in turn is enmeshed in the regional drought-related water crisis throughout the seven Colorado River Basin states, which are being told by the federal government that 2 million to 4 million acre-feet in water use must be cut by next year to keep reservoirs like lakes Mead and Powell from dropping to critically low levels.
As the state works to address its water issues and plan for future growth, Miller said he and others in Pinal expect it will turn to groundwater, surface water from lakes and rivers and recharging underground resources with treated wastewater as a “three-pronged” approach.
“This all goes to show we need to be good stewards of our environment, and we need to understand it,” he said. “We’re not going to fix this problem by conservation, you couldn’t cut down enough water to change the numbers that fast anytime soon, so we have to find this multi-pronged solution and better understand our aquifer.”