Extensive UCSB groundwater study shows risk of wells running dry across globe, including California

Apr 29, 2021

Researchers from the University of California at Santa Barbara have published the most extensive analysis to date on groundwater infrastructure across the globe. Their research calls attention to the high number of wells at risk for running dry, including along the Central Coast.

Around the world, billions of people rely on wells for drinking water and crop irrigation, but that reliance is being threatened by changes in groundwater levels.

“When wells run dry, people lose access to a water supply to their homes, and people lose access to a reliable source of water to produce crops that support their livelihoods,” said Debra Perrone, assistant professor in UCSB's Environmental Studies Program.

Perrone worked with fellow UCSB Assistant Professor Scott Jasechko to map and study the vulnerability of wells as a water source. The environmental scientists spent about six years analyzing 134 different data sets from 40 countries.

Perrone said the study found that the depth at which most wells are drilled may soon be inadequate for extracting water, due to declining water tables.

“One in five wells are not much deeper than their local groundwater level,” Perrone said.

The global study includes California, and Perrone said groundwater levels are declining in areas of the Central Coast. She said each county has its own portfolio for water — often tapping into a variety of sources — however, certain rural areas rely solely on groundwater.

Declining groundwater is a complex issue with many contributing factors. Jasechko said drought is one factor.

“One of the direct impacts is a reduction in the rate that the resources are recharged or replenished, so there’s just less precipitation trickling into the groundwater replenishing it," Jasechko said. "There are also indirect impacts. For example, during droughts we tend to find that reliance on groundwater increases."

Drilling deeper wells might seem like a way to extract more water, but Jasechko said that is not a long-term solution. Groundwater, he said, is like a bank account beneath our feet. The balance keeps going down unless we stop withdrawing or make a deposit.

The researchers said the solution is likely a combination of behavioral changes, enhanced farming techniques, groundwater replenishment efforts, and new policies.

The groundwater study is the cover article of the April edition of the journal “Science.”