Spatiotemporal distribution of strain field and hydraulic conductivity at the Phoenix valley basins, constrained using InSAR time series and time-dependent models

Abstract:

<span">Poroelastic theory suggests that long-term aquifer deformation is linearly proportional to changes in pore pressure. Land subsidence is the surface expression of deformation occurring at depth that is observed with dense, detailed, and high precision interferometric SAR data. In earlier work, Miller & Shirzaei [2015] identified zones of subsidence and uplift across the Phoenix valley caused by pumping and artificial recharge operations. we combined ascending and descending Envisat InSAR datasets to estimate vertical and horizontal displacement time series from 2003-2010. Next, wavelet decomposition was used to extract and compare the elastic components of vertical deformation and hydraulic head data to estimate aquifer storage coefficients. In the following, we present the results from elastic aquifer modeling using a 3D array of triangular dislocations, extending from depth of 0.5 to 3.5 km. We employ a time-dependent modeling scheme to invert the InSAR displacement time series, solving for the spatiotemporal distribution of the aquifer-aquitard compaction. Such models are used to calculate strain and stress fields and forecast the location of extensional cracks and earth fissures, useful for urban planning and management. Later, applying the framework suggested by Burbey [1999], the optimum compaction model is used to estimate the 3D distribution of hydraulic conductivities as a function of time. These estimates are verified using in-situ and laboratory observations and provide unique evidence to investigate the stress-dependence of the hydraulic conductivity and its variations due to pumping, recharge, and injection. The estimates will also be used in groundwater flow models, enhancing water management in the valley and elsewhere. <span">References <span">Burby, T. J. (1999), Effects of horizontal strain in estimating specific storage and compaction in confined and leaky aquifer systems, Hydrogeology Journal, 7(6), 521-532, doi:10.1007/s100400050225. <span">Miller, M. M., and M. Shirzaei (2015), Spatiotemporal characterization of land subsidence and uplift in Phoenix using InSAR time series and wavelet transforms J. Geophys. Res. Solid Earth, 120, doi:10.1002/2015JB012017.