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Abstract

In California’s San Joaquin Valley, groundwater overdraft has caused dramatic and continued land subsidence during two main periods, 1925–1970 (“the historic period”) and post-2006. The impacts of the subsidence are severe, with modified flood risks, damaged aqueducts, and permanently altered aquifer dynamics. However, we do not have a complete record of the post-2006 subsidence due to a 2011–2015 gap in Valley-wide observations, and this makes it difficult to develop an appropriate management response. Here, we used satellite geodetic subsidence measurements to quantify the Valley-wide subsidence volume during 2006–2022. We found a total subsidence volume of 14 km3 over the 16 years, the same as was measured during 24 years of monitoring in the historic period. Considering the extraordinary 2006–2022 Valley-wide subsidence, we make high-level recommendations for subsidence mitigation, highlighting the importance of focusing groundwater overdraft reductions on the deeper aquifers where subsidence originates, and on localities where subsidence impacts are greatest.