Airborne geophysical method images fast paths for managed recharge of California’s groundwater

Abstract Given the substantial groundwater level declines in Central Valley of California, there is an urgent need to supplement recharge systems by implementing managed aquifer recharge. With approximately 170 km 3 (140 million acre-feet) available storage space, water deemed be excess during wet years could spread on ground surface at selected locations allowing it move downward underlying system. Along eastern edge are large paleovalleys that can act as fast paths expediting movement water. These paleovalleys, incised and then filled with coarse-grained materials—sand, gravel, cobbles—at end last glacial period, referred valley fill (IVF) deposits. An IVF deposit has been mapped one location Kings River alluvial fan, others proposed exist fans major rivers. If located, these deposits would optimal sites for In this study, we assessed use a helicopter-deployed geophysical method efficiently locate throughout Valley. We acquired 542 line-kilometers airborne electromagnetic (AEM) data dense line-spacing over which had ∼2 wide, extending 20 into Valley, from depth 30 m. The was unambiguously imaged AEM extensive linear feature more electrically resistive than surrounding materials due high percentage sediments. This study provides evidence support rapid adoption along provide valuable natural infrastructure recharging California’s groundwater.