Why Is That Helicopter Towing a Giant Hula-Hoop? DWR Conducting Airborne Electromagnetic Surveys Later This Month

The following is a press release issued by the County of Mendocino:

[Picture of an aerial electromagnetic survey provided by the United State Geological Survey]

The California Department of Water Resources (DWR) is using an innovative, helicopter-based technology to gather information about the state’s groundwater aquifer structure to support drought response and the implementation of the Sustainable Groundwater Management Act (SGMA).

Beginning November 11, 2021, DWR will conduct AEM surveys of groundwater basins in Mendocino, Sonoma, and Lake Counties, specifically around Ukiah, Big Valley, Petaluma, Santa Rosa Plain, and Sonoma Valley. The helicopter crew may run test flights several days prior to the start of the surveys as well. The survey schedule can be accessed from DWR’s AEM webpage or directly from the following link:

During the surveys, a low-flying helicopter tows a large hoop with scientific equipment approximately 100 feet above the ground surface. The helicopter, flown by experienced and licensed pilots, will make several passes over the survey areas and may be visible to residents.

Survey data creates an image of the subsurface down to a depth of about 1,000 feet below ground surface and provides information about large-scale aquifer structures and geology. This information will help support the implementation of the Ukiah Valley Groundwater Sustainability Agency’s (UVBGSA) Groundwater Sustainability Plan. For more information, please watch DWR’s short 2-minute video on the introduction to the AEM method, provided in both English and Spanish.

The AEM method is safe, and surveys have been conducted successfully in several locations throughout California. Surveys will be conducted during daylight hours only, and the helicopter will not fly over businesses, homes, other inhabitable structures, or confined animal feeding operations. The helicopter operator follows all established Federal Aviation Administration rules and regulations and their highest priority is public safety. Experienced pilots, who are specially trained for the low-level flying required for geophysical surveys, will operate the helicopter.For more information about the AEM surveys, visit DWR’s AEM project website. For questions, please email

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