Présentations Colloques

Oral Presentation
8.11
Session 8.11: Hydrogeodesy: new surface tools to characterize and monitor active and managed groundwater systems
Castellazzi Pascal
InSAR to understand groundwater flow systems and support groundwater management
Interferometric Synthetic Aperture Radar (InSAR) is used increasingly more in hydrogeology. According to the poro-elastic model, hydrostatic pressure changes induce grain-to-grain spacing changes within an aquifer matrix and deformation at the surface. Pressure changes can be related to either natural processes, e.g., temporal patterns of recharge discharge which induces storage variations, or have anthropogenic causes- e.g., pumping, artificial recharge. Aquifer storativity and confinement are among the main governing parameters controlling the amplitude of the deformation, as it relates to the pressure changes implied by a given inflow or outflow rate. InSAR efficiently monitors these ground deformations. It is non-invasive, has large spatial coverage, a temporal frequency of at least 24 days, and a precision of up to a few mm yr. Through different case studies conducted by our research group in Canada and Mexico, this presentation provides an overview of the applicability of InSAR for groundwater studies.**At local scales, InSAR provides important spatial information related to the lithological heterogeneity of depleting compressible aquifers- e.g., litho-stratigraphic boundaries or clay interbed thickness. It also provides information related to groundwater flow patterns, e.g., temporal variation of recharge and pumping areas. In karstic settings, Persistent Scatterers Interferometry (PSI) is particularly suitable to reveal preferential flow path and mitigate related damages to infrastructures. **From regional to continental scales, InSAR provides guidance to improve large-scale groundwater governance schemes. By yielding the missing spatial details within GRACE-derived groundwater storage trend estimates, it could be used to improve its precision and scale of application. Thus, integration of InSAR-derived ground deformation maps into GRACE data holds promises in the perspective of high resolution and volumetric mapping of depleting groundwater resources.
Canada