In a groundbreaking effort to monitor California's precious water resources, NASA is deploying sophisticated radar technology to track underground water movement in the San Joaquin Valley.
A specially equipped NASA Gulfstream-III aircraft, carrying the Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR), is conducting a series of six flights over a 25-mile stretch of the Tulare Basin in 2025. This area, where the Sierra Nevada mountains meet farmland, is critical for understanding how snowmelt replenishes groundwater supplies.
"For generations, we've been managing water in California without truly knowing where that meltwater seeps underground and replenishes groundwater," explained Stanford University geophysicist Rosemary Knight, who leads the research project.
The UAVSAR system can detect minute ground movements - smaller than the thickness of a nickel - caused by water pressure as it moves underground. While invisible to the human eye, these subtle surface bulges create what researchers call an "InSAR recharge signature," helping pinpoint where and how quickly water is absorbed into depleted aquifers.
This precision mapping holds particular importance for the San Joaquin Valley, which produces over one-third of America's vegetables and two-thirds of its fruits and nuts. Local farmers heavily depend on groundwater, especially during drought periods.
"In dry years, when we get limited opportunities, we can direct flood releases to areas that recharge efficiently," said Aaron Fukuda, general manager of the Tulare Irrigation District. "In wetter years, we need to move water into the ground quickly to prevent flooding and maximize absorption."
The project is part of NASA's broader water monitoring initiatives, which include upcoming satellite missions like NISAR - a joint venture with India's space agency that will track surface changes globally every 12 days.
By combining airborne radar surveys with satellite observations, NASA aims to provide water managers with unprecedented insight into groundwater movement, helping protect this valuable resource for agriculture and communities across California's Central Valley.