Negotiators have moved painstakingly as they reached a fragile agreement to preserve our water supply from the Colorado River.

But that same deal protecting water supplies to the urban areas of Arizona also exacerbates an even more protracted problem — overdrawing Arizona’s groundwater, especially in rural areas.

To preserve water supplies for Pinal County farmers, the deal weans them off Colorado River water supplied by the Central Arizona Project and returns them to relying on groundwater alone by 2026. The deal, if approved, would help them stick longer straws into the ever-lower aquifer, so they stop using the river water that cities like Tucson and Phoenix depend on.

That change, of course, is unsustainable. Pinal County has already suffered subsidence and long cracks in the earth due to sucking up too much groundwater.

But the problem isn’t just Pinal County — it’s expanding desert agriculture in combination with booming population.

By returning to groundwater, Pinal County farmers once again become part of a broader Arizona problem: Too little control over how much this underground public resource is used. The Legislature has shown no will to intervene, which means groundwater levels will continue to drop, and it will become increasingly unaffordable in some areas to sink wells and reach water. Increasingly, only the well-off will be able to reach it.

The Legislature will have trouble just passing the deal to keep water in the Colorado River, but it ought to go on and confront the groundwater problem, even if it means tangling with entrenched interests. Don’t expect them to do it, though, thanks in part to a Southern Arizona legislator, Rep. Gail Griffin. But more on her later.

Rep. Regina Cobb, a Republican from Kingman, has seen just how hard it can be to move the Legislature to support even a study of groundwater. Cobb represents Mohave County, where agricultural business has moved into places like the Hualapai Valley and taken advantage of the state’s liberal groundwater laws. She has tried twice and failed to get the Legislature to fund studies of groundwater usage.

The 1980 Groundwater Management Act created five “active management areas” where groundwater pumping is controlled. Those cover the Prescott, Phoenix, Pinal County, Tucson and Santa Cruz County areas. Outside of these AMAs, as they are known, anyone can sink a well and pump as much groundwater as they want.

It’s an unsustainable law, especially in a time when agribusiness is searching for places with cheap access to plentiful water.

But two major forces have worked against doing anything about it, even studying the problem: Arizona agriculture and a “Don’t tread on me” ethos.

Cobb acknowledged when we spoke Friday that those twin powers have so far defeated her efforts to mandate outside study of the groundwater in the Hualapai Basin and elsewhere in her Northwestern Arizona home district.

“We wanted to be the land of the free. Now that we have a lot of farming and pumping coming in, now we’re kind of concerned,” Cobb said.

But agricultural interests have been concerned that studies of water use are tantamount to “the camel’s nose under the tent,” the first step toward future regulation.

“My thought is that if we don’t know what’s going on, if we let people drop pumps wherever they want to, we’re going to run out of water,” Cobb said.

She’s right, and it’s especially true in her Northwestern Arizona area as well as agricultural areas of Southeastern Arizona, especially around Willcox and elsewhere in Cochise County.

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But the idea that groundwater is a private property right dominates the Legislature and is embraced by Griffin, the Cochise County legislator with power over water. Griffin was a senator but won election to the House this year and was selected chair of the Natural Resources, Energy and Water Committee.

It will be in Griffin’s power to kill outright any water bills she doesn’t like. And in recent years, her tendency has not been to seek protections of groundwater. She’s sought to remove them by requiring the boards of supervisors in counties like Cochise to unanimously renew the existing requirement of a 100-year water supply for any new development.

I spoke with Sarah Porter, director of the Kyl Center for Water Policy at ASU, and she said there need to be changes in state law that allow for nuance in dealing with local groundwater issues. But she insisted rural users broadly need protection.

“I look at these places, and I feel like they’re so vulnerable,” Porter said. “There are people who have been farming in the Willcox area for generations. They’re very vulnerable if big industrial ag can move in and change, exponentially, the rate of withdrawal of groundwater.”

Porter moderated a Dec. 7 forum at the Sandra Day O’Connor Institute and was pleased to hear some openness from House Speaker Rusty Bowers to the idea of measuring water pumping by large users, something that has been vehemently opposed by agricultural interests before.

Answering a question from Porter, Bowers said: “Examinations of metering and water usage statewide, I think that’s in our future.” With Griffin heading the water committee, I cannot imagine a metering program passing.

But perhaps the most fundamental point was made by Bowers’ colleague on the panel, Kathy Ferris, who helped shepherd the 1980 groundwater act into law.

“The groundwater in Arizona is a public resource,” she said. “While a lot of folks still like to believe they own the water under their ground, they do not. It is owned by the state of Arizona for the benefit of the public good.”

Beyond the Colorado River deal, this is what legislators owe us this session: Taking groundwater seriously as a public resource and at minimum moving forward with efforts to measure how much is being used. Anything less is a dereliction of duty.

Contact: tsteller@tucson.com or 807-7789. On Twitter: @senyorreporter

Columnist

Tim Steller is the Star’s metro columnist. A 20-plus year veteran of reporting and editing, he digs into issues and stories that matter in the Tucson area, reports the results and tells you his opinion on it all.