California is thirsty and needs all the help it can get toward saving and extending water supplies.  In 2014, California's Sustainable Groundwater Management Act was established to protect groundwater resources that comprise approximately 38 percent of the state’s water supply during normal years, increasing to as much as 60 percent during drought-ridden years and as much as 100 percent in certain communities.[1]  Last year, the state introduced airborne electromagnetic (AEM) surveys as a means of gaining insight into the attributes of its groundwater basins, information that will be instrumental to groundwater sustainability agencies (GSAs) in the creation of state groundwater sustainability plans (GSPs) as required by the Act.

California has 515 groundwater basins that have been classified based on priority of water needs and using this classification system the state plans to survey 100 high- and medium-priority basins.  The technology is deployed using a helicopter that has a 100-foot-long hexagonal-shaped tool that generates a current, sending electromagnetic signals 1,000 feet into the earth that bounce back, providing images that are interpreted to calculate aquifer water levels, the process likened to an MRI for the Earth.[2] The AEM surveys will provide insight not only as to best practices for groundwater management but also the best approaches for aquifer recharge while highlighting those demanding immediate attention.

The California Department of Water Resources has reported that the Airborne Electromagnetic Survey project will cost the state $12 million and is funded by Proposition 68, Senate Bill 5, and from the general fund.  The surveys were completed in May 2022 and data is available for some of the survey areas and will continue to roll out through mid-2023. 


[1] State of California. “Groundwater.” Department of Water Resources, 2022,

[2] Sanchez, Edgar. “'MRI for the Earth' Probes Groundwater from the Air in California - Tool Is Able to Send Electromagnetic Signals 1,000 Feet into the Earth's Subsurface.”, 16 May 2022,