Half the Groundwater Sustaining US Produce Isn't Coming Back

What did the study find about California?

California dominates. It's the country's irrigation hotspot for specialty crops, and the Central Valley leans hardest on groundwater there — more than 90% of it from unsustainable pumping. Even regions with huge aquifers, like the Midwest's Ogallala and the Mississippi Embayment, send very little groundwater toward fruits, nuts and vegetables.

Florida offers the contrast. Most of its irrigation draws surface water, with 60% going to sugarcane and 32% to oranges.

"This [data] is very useful for assessing risk to different crops, because the risks differ substantially depending on whether crops are surface-water-fed or groundwater dominant," said Nathan Mueller, an environmental scientist at Colorado State University. Surface-water-fed crops face drought and shifting rainfall. Groundwater-fed crops face aquifers that eventually run dry.

Almonds sit at the top of the depletion list. Over a quarter of all aquifer-depleting irrigation went to almonds alone, and almonds — like pistachios, tomatoes, grapes, peppers and garlic — draw 90% to 100% of their groundwater from nonrenewable pumping.

"I've always heard that almonds use a lot of water, but this seemed almost too shocking to be true," Hanley said.

Berries are the other end of the spectrum. Raspberries, blackberries, blueberries and cranberries use the lowest proportion of nonrenewable groundwater.

What happened during the drought?

The 2012–2017 California drought pushed farms even deeper into the red. As surface supplies became unreliable, irrigation shifted from a little over 50% groundwater to nearly 70% — nearly all of it unsustainable pumping.

The data suggest that shift stuck. Farmers have continued the groundwater-heavy pattern since the drought ended, and combined with pumping for non-specialty crops, that raises an uncomfortable question: how long can the Central Valley's aquifers hold out?

"It's not unreasonable to say, in the short term, we are using this resource unsustainably to meet current demand," Hanley said.

What can be done with the numbers?

The study's value lies in its specificity, its authors argue. A county-level inventory lets farmers and policymakers pinpoint which crops and locations offer the biggest water savings from efficiency improvements or changing what gets grown where.

"I've come to really value place-specific data and place-specific solutions," Hanley said. "The most effective solutions are tailor-made for the environment that they exist in."

Mueller sees a role for shoppers too. "I think it's very good for consumers to be aware of the way that the products they're buying trace back to some of these sustainability issues," he said.

The study has limits worth flagging. It covers 2008–2020, so it doesn't capture the most recent dry years, and it estimates withdrawals rather than measuring every well. Still, it replaces guesswork with a map — and the map says America's produce aisle is running on water it can't replace.