California isn’t convinced that Napa County is adequately managing groundwater that sustains the area’s vineyards, wineries, rural residents and Napa River fish.

State Department of Water Resources officials emphasized they aren’t claiming well water use is harming the subterranean reservoir beneath the Napa Valley floor. Rather, they said a more than 1,000-page basin report submitted by Napa County doesn’t allow them to make a judgement.

“The department staff found no evidence that the county had managed the subbasin within its sustainable yield over a period of at least 10 years,” a letter to the county from Taryn Ravazzini of the Department of Water Resources stated.

Unless the county convinces the state to reverse this tentative finding, it will have to form a groundwater sustainability agency to create a Napa Valley subbasin sustainability plan. The county maintains it has done the equivalent of this work, while some local environmentalists disagree.

The county has 30 days to convince the state it is mistaken. County officials said they are reviewing the Department of Water Resources report and will submit a response to the agency.

Angwin resident Mike Hackett wants the county to form a groundwater agency. He questioned the approach to groundwater that county officials have taken so far with a consulting firm.

“They want to be told everything is fine, when, in fact, it’s not fine,” Hackett said.

Hackett wants the county to go beyond what the state is requiring. He favors a holistic approach that looks at the Napa Valley subbasin, other local groundwater basins, the Napa River and waterways, as opposed to what he sees as a segmented approach.

“All of our water resources are connected,” Hackett said. “Everything is connected.”

Napa County is responding to a state push to ensure that communities don’t overtax groundwater supplies. The state’s groundwater program began in 2014. Researchers say unregulated groundwater use over decades has caused parts of the San Joaquin Valley to subside as much as two inches a month.

California requires communities in certain groundwater basins to form groundwater sustainability agencies. However, it allows communities to avoid taking this step if they can show they are already doing a good job managing groundwater.

Napa County defined “sustainability” as using groundwater “in a manner that can be maintained indefinitely without causing unacceptable economic, environmental or social consequences, while protecting economic, environmental and social benefits.”

But the county didn’t set thresholds of when groundwater use would produce significant and unreasonable effects, Department of Water Resources staff concluded. Nor did the county manage the Napa Valley subbasin to any threshold.

“Because the county has not established such thresholds or defined conditions giving rise to undesirable results, the county can only speculate whether undesirable results have occurred,” state Department of Water Resources staff wrote.

This assessment in no way diminishes efforts by Napa County to understand more about groundwater, state staff wrote. These efforts will likely be a foundation to develop a groundwater sustainability plan.

Napa County’s 2016 Napa Valley basin analysis report found that the Napa Valley subbasin has a sustainable yield of 17,000 acre-feet to 20,000 acre-feet annually. Pumping at the time – which was during a drought—averaged 17,506 acre-feet annually. One acre-foot is about 326,000 gallons.

Pumping in 2017 was 15,831 acre-feet and in 2018 was 17,889 acre-feet, the county Board of Supervisors heard at its March 19 meeting. The cumulative annual storage change in the subbasin over 30 years is positive 4,388 acre-feet.

“The fact is, we’re pumping,” Supervisor Alfredo Pedroza said at the meeting. “But the fact is it is within the sustainable yield.”

But the county has yet to prove this to the state’s satisfaction.

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Napa County Reporter

Barry Eberling covers Napa County government, transportation, the environment and general assignments. He has worked for the Napa Valley Register since fall 2014 and previously worked 27 years for the Daily Republic of Fairfield.