Land Subsidence over Densely Vegetated Aquifers in Texas and California

In this study, we derive time series histories over the southern Central Valley and the Carrizo-Wilcox aquifer using spaceborne Interferometric Synthetic Aperture Radar (InSAR) techniques. The observed subsidence signals are associated with withdrawal of fluids from the subsurface, either from confined aquifer pumping or oil and gas production. We processed 122 C-Band Sentinel-1 SAR images over the Central Valley and 123 images over a ~100 x 200 km region near San Antonio, TX from 2017-2021. These InSAR datasets suffer from severe decorrelation artifacts due to the presence of dense vegetation. To overcome this limitation, we use a recently developed Persistent Scatterer (PS) algorithm to reconstruct spatially coherent phase patterns in decorrelated interferograms. We derived SBAS solutions using varying temporal baselines using original, uncorrected data and PS-interpolated interferograms. In the Central Valley, computing all interferograms and selecting those with minimal unwrapping artifacts result in the smallest linear rate misfit when compared to independent GPS data. Using this strategy over the San Antonio site, we observe a region over 100 km long of up to 10 cm of cumulative line of sight (LOS) subsidence overlaying the Eagle Ford shale. Subsidence mapping over the large-scale, complex, vegetated aquifers will help transform our understanding of groundwater resources and their sustainable management.