Understanding the geodetic signature of large aquifer systems: Example
of the Ozark Plateaus in Central United States
Abstract
The continuous redistribution of water mass involved in the hydrologic
cycle leads to deformation of The continuous redistribution of water
involved in the hydrologic cycle leads to deformation of the solid
Earth. On a global scale, this deformation is well explained by the
loading imposed by hydrological mass variations and can be quantified to
first order with space-based gravimetric and geodetic measurements. At
the regional scale, however, aquifer systems also undergo poroelastic
deformation in response to groundwater fluctuations. Disentangling these
related but distinct 3D deformation fields from geodetic time series is
essential to accurately invert for changes in continental water mass, to
understand the mechanical response of aquifers to internal pressure
changes as well as to correct time series for these known effects. Here,
we demonstrate a methodology to accomplish this task by considering the
example of the well-instrumented Ozark Plateaus Aquifer System (OPAS) in
central United States. We begin by characterizing the most important
sources of groundwater level variations in the spatially heterogeneous
piezometer dataset using an Independent Component Analysis. Then, to
estimate the associated poroelastic displacements, we project geodetic
time series corrected for hydrological loading effects onto the dominant
groundwater temporal functions. We interpret the extracted displacements
in light of analytical solutions and a 2D model relating groundwater
level variations to surface displacements. In particular, the relatively
low estimates of elastic moduli inferred from the poroelastic
displacements and groundwater fluctuations may be indicative of aquifer
layers with a high fracture density. Our findings suggest that OPAS
undergoes significant poroelastic deformation, including highly
heterogeneous horizontal poroelastic displacements.