Results from groundwater pumping-induced subsidence model, San Joaquin Valley

The San Joaquin Valley, California has experienced dramatic subsidence
over the past 100 years, but the regions with the most subsidence have
shifted dramatically over this time period, from west (Kettleman City/Los
Banos) to south (Tulare/Pixley/Corcoran). To date, no study has done an
in-depth analysis of the mechanisms driving this shift in subsidence. We
analyze head records, utilizing a novel approach that assimilates change
in head data from multiple overlapping time periods, to produce an 80-year
record of change in head over both the historical and modern regions of
greatest subsidence. We then calibrate a deformation model to fit both
historical (measured with leveling surveys) and modern (measured with
Interferometric Synthetic Aperture Radar, or InSAR) datasets. We find that
the stress history of the Kettleman City/Los Banos region with
historically high subsidence plays a large role in reducing modern
subsidence in that region, while declining heads in both regions are
likely to result in major subsidence over the next several decades. This
study highlights the need for active groundwater management to mitigate
ongoing and future subsidence. One key dataset needed in this effort is
accurate long-term head histories to reconstruct the stress history of
aquifers for accurate deformation modeling.