Routine monitoring of subsidence in California's Central Valley using Interferometric Synthetic Aperture Radar (InSAR)

Subsidence caused by groundwater pumping in the rich agricultural area of California's Central Valley has been a problem for decades. Over the last few years, InSAR observations from satellite and aircraft platforms have been used to produce maps of subsidence with cm accuracy. At JPL, with funding from the California Dept. of Water Resources (DWR) we began processing InSAR data from multiple satellites covering the period 2007 - present. Maps and other information products were furnished to decision-makers at the DWR to enable better management of groundwater resources.

Recently, we have begun the transition to a more robust processing system at JPL called ARIA (Advanced Rapid Imaging and Analysis; see http://aria-products.jpl.nasa.gov/). ARIA produces open-access standard InSAR displacement products from Sentinel-1 data at 90 m resolution. The system is scaled to keep up with Sentinel-1 data of many areas of interest, including California and will be called upon to process data from the upcoming NISAR (NASA-ISRO SAR) mission. The DWR project is a test case for the use of ARIA to produce time series for users with little or no InSAR expertise for further analysis.

Maps produced so far show two large areas of subsidence in the southern Central Valley which subsided at a maximum rate of about 27 cm/yr until about 2014 when the rate increased to 40 cm/yr due to the drought. Recent rains in California caused a pause, and even a rebound in some of these areas.

Work is continuing on using subsidence and ancillary data from wells to produce a better understanding of how these aquifers respond to water inputs and outputs both spatially and temporally. This should allow a predictive capability, potentially defining sustainable pumping rates related to local hydrogeology and water inputs.

* work performed under contract to NASA and the CA DWR