Quantification of record-breaking subsidence in California’s San Joaquin Valley

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. A remote-sensing based quantification of land subsidence in the San Joaquin Valley, California, finds that recent land subsidence has matched the totals recorded historically, and suggests limiting groundwater withdrawal from deeper parts of the aquifer system.