Credit: Julia B. Chan/Reveal

California needs to build urban aquifers beneath its cities to help manage future droughts and ensure the state has enough water in coming decades, according to analysis released Tuesday by the Union of Concerned Scientists.

The nonprofit group, founded by MIT scientists in 1969, analyzed California’s long-term water security and concluded that the state needs to build underground water storage systems beneath cities to capture storm runoff, which then can be used later during drought years.

The concept is not new to California, with Los Angeles County receiving state approval this summer to pursue underground storage, but there has been no statewide effort like that recommended in Tuesday’s report.

It is part of the union’s overall recommendation that the state begin developing better underground infrastructure – in both rural and urban areas – to store water in the face of a warming climate, which scientists forecast will bring more radical weather swings, including longer droughts followed by record-setting downpours.

“Sustainable groundwater management can help protect California from both severe droughts and severe floods,” the report says. “This can help reduce flooding and also prepare us for dry periods, when we can use the stored water.”

Groundwater management has become a critical point of focus during the drought, as aquifers provide up to 60 percent of the state’s water supply during dry years. With so much water being pumped up to make up for the loss of rain and snow, the state’s aquifers are being drained.

The state now is pumping water that seeped underground more than 20,000 years ago. And as the aquifers are drained, the land above them sinks, resulting in parts of the Central Valley falling at a rate of 2 feet per year, creating potentially billions of dollars of damage to roads, canals and bridges on the surface.

The state has done little to track the damages that result from this historic sinking, including damage to its critical flood levees, which have dropped more than 6 feet.

Nathan Halverson (he/him) is an Emmy Award-winning producer for Reveal, covering business and finance with a current emphasis on the global food system. Before joining Reveal, Halverson worked on projects for FRONTLINE, the Investigative Reporting Program at the UC Berkeley Graduate School of Journalism and PBS NewsHour. He was the principal reporter on Reveal's story about the Chinese government’s involvement in the takeover of America’s largest pork company, Smithfield Foods Inc. He was awarded a 2014 McGraw Fellowship by the CUNY Graduate School of Journalism, and he received a bachelor's degree in economics from the University of Minnesota. He has won a New York Times Chairman’s Award and has received reporting honors from the Society of American Business Editors and Writers, California Newspaper Publishers Association, San Francisco Peninsula Press Club and Associated Press News Executives Council. Halverson is based in Reveal’s Emeryville, California, office.