GW Fluxes across boundaries forcaSTing by combined hydrogeophysics data and model – GWSBOUND

Groundwater (GW) systems exist in dynamic balance with the climate and human pressure, connecting interfacing zones of recharge and discharge with multiple feedbacks. Quantifying the aquifer recharge and the stream-aquifer is a key issue for hydrogeologists to consider the safe yield and good water quality, especially in view of the ongoing changes in climate and land use. The objective of GWSBOUND is to provide monitoring and predictive tools of the water fluxes through these interfaces by the combined uses of hydrogeology, poroelasticity, petrophysics and geophysics approaches. The fully combined hydrogeophysics tools will improve the accuracy of groundwater models, aid in uncertainty assessment of its parameters by the uses of advanced numerical modelling, probabilistic, deep learning inversion approaches and spatiotemporal interpolation using the geostatistical approaches. The great novelty resides in the use of geophysical and hydrogeological data that are directly dependent on the water content storage, temperature and water level temporal variations. GWSBOUND will proceed in five main steps: developing a High-Performance numerical model to couple the groundwater and geophysical model through poroelastic and petrophysic models, create synthetic cases to realise a sensitivity analysis of the different heterogeneity configuration and hydrogeological regime on the hydrothermal and seismic wave responses, develop the workflow of the combined hydrogeological and geophysical inversion, apply this tool to the outlet of the Orgeval Critical Zone Observatory in current climatic conditions, and finally simulate the responses of the water resources to various IPCC scenarios of climate change (CMIP6 projections). The Orgeval Critical Zone Observatory (CZO) represents an opportunity to apply the combined inversion, for which an important database exists thanks to the French research program PIREN-Seine and the OZCAR research infrastructure.