A new analysis of groundwater levels across California has found historically low water levels in thousands of wells in all areas of the state, another telltale of the drought’s intensity.
The report by the California Department of Water Resources, released Wednesday, was ordered by Gov. Jerry Brown as part of his January emergency drought proclamation. It analyzes thousands of wells across the state, based on available data submitted by well drillers and owners.
In examining about 5,400 wells that represent a subset of the total, about half have shrunk since 2008 to water levels lower than any seen over the preceding century.
The San Joaquin Valley is particularly hard hit, where wells are commonly used to irrigate large farms when water diverted from rivers becomes unavailable. Many of those wells have groundwater levels as much as 100 feet lower than historical norms, according to the report. Many wells in the Sacramento Valley, the Sonoma Valley and the Los Angeles basin have shrunk as much as 50 feet.
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“There are an awful lot of areas that have gone drier,” said Mary Scruggs, a supervising engineering geologist at DWR who helped produce the report.
In droughts, property owners typically rely more heavily on wells because surface water from rivers and streams becomes scarce or more expensive. Yet the results are particularly alarming because they are based on springtime well measurements, when groundwater levels typically peak. As summer arrives in this third drought year, demand on wells is expected to increase.
The report also looks at how often existing wells have been deepened so that pumps can reach a shrunken aquifer. This is often a sign of drought stress. DWR found that, since 2010, three Sierra Nevada foothill counties in the Sacramento region – Placer, El Dorado and Nevada – lead the state in well deepening by a large margin.
Greg Peters, owner of Peters’ Drilling and Pump Service in Auburn, said he has definitely seen an increase in business lately, apparently in response to the drought, but not a “huge influx.”
A number of customers who own large landscaped properties are having wells drilled or deepened to prepare for the dry summer. In case their regular water provider reduces their supply of irrigation water, he said, they want to have another water source to keep lawns and gardens flourishing.
“People are saying, well, in case this happens, I want to be ahead of the game,” Peters said. “We are seeing increases in deepening of wells. But mostly it’s wells that were marginal wells to begin with.”
California is one of the few states that does not regulate how much water well owners can pump. The state also does not require well owners to report how much they pump. Most of the information in the report comes from a database of well-water elevation that relies on volunteer reports and wells monitored by DWR or another public agency. It also relies on reports that must be filed by well-drilling companies, although these reports are held confidential by DWR under provisions of the state Water Code.
In 2009, new state legislation required well owners to regularly report ground water elevation (but not pumping rates) or risk losing eligibility for state water grants. Compliance has been spotty: According to the report, about one-third of the state’s high- and medium-priority groundwater basins are still not reporting water elevations, although most are working to join the program.
Scruggs said she hopes the report will encourage the public and water agencies to plan their groundwater use more carefully. In average years, groundwater serves 30 percent to 40 percent of California’s water needs. In drought years, this often increases to 60 percent.
“I think people aren’t always aware of the status of groundwater and how important it is,” Scruggs said. “Groundwater is a critical resource. I think we should be protecting and managing our groundwater.”