Even though California enacted sweeping legislation nearly a decade ago to curb excessive agricultural pumping of groundwater, new research predicts that thousands of drinking water wells could run dry in the Central Valley by the time the law’s restrictions take full effect in 2040.

The study, published this month in the journal Scientific Reports, casts critical light on how the state is implementing the 2014 Sustainable Groundwater Management Act. The research reveals that plans prepared by local agencies would allow for heavy pumping to continue largely unabated, potentially drawing down aquifers to low levels that would leave many residents with dry wells.

The researchers warned that unless local agencies adopt more stringent measures or come up with backup plans, many people in the Central Valley could be left without access to drinking water, and low-income communities could be severely affected.

Study authors reviewed 60 local groundwater plans throughout the Central Valley and examined a key metric called minimum thresholds — the aquifer levels groundwater agencies have set as lower limits while they implement the groundwater act’s rules and restrictions over the next 16 years.

They found that more than 5,000 domestic wells would be left completely dry, while an additional 4,000 household wells would be “partially dewatered,” leading to problems such as low water pressure or damaged pumps.

In all, they said, more than 9,200 household wells and 1,000 public supply wells could fail if water levels are allowed to decline to the plans’ minimum thresholds.

“The numbers are quite large and have the potential to impact many, many people,” said Darcy Bostic, a researcher with the West Sacramento-based. nonprofit Rural Community Assistance Corp., who led the study.

Bostic and her colleagues found that plans submitted by local agencies would allow major declines in groundwater between now and 2040. They said the thresholds allow for aquifer levels to decline, on average, 80 feet below 2019 levels , while some agencies set their thresholds more than 200 feet below current levels.

Such large drops would closely resemble “status-quo, business-as-usual” declines driven by unrestricted pumping, the researchers said. They urged state and local water officials to strengthen protections for drinking water wells and take steps to mitigate the effects.

“If we are not careful or aware of this, impacts to drinking water access and even to agricultural economies may be severe,” Bostic said. “I hope that there’s a conversation around how we can support particularly rural and lower-income communities that will be impacted by declining groundwater levels.”

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