Thesis defense of Luca GUILLAUMOT

How to model groundwater systems in the hydrological cycle ? An approach at different scales with different observed data types

Abstract

Groundwater systems transiently store water and transfer them laterally to feed to rivers and support evapotranspiration at time scales from the month to hundreds of years. They are a major resource for human and ecosystems. Predicting the response of groundwater to anthropogenic and climate pressures is limited by (1) the scarcity of direct information on the highly heterogeneous geological media (2) the complexity of surface-depth exchanges.
In this thesis, we study the signature of surface-deep exchanges on different direct and indirect observables (piezometry, river flow, deformation, evapotranspiration ...) and their ability to inform simple hydrogeological models. We rely on models at the local (km) and continental scale. Both approaches illustrate the control of topography, geology and heterogeneity on groundwater flow. We highlight the complementarity of the different types to better constrain surface-depth exchange processes.