River Corridor Model Constrained by Time-Lapse Seismic Acquisition

A new hydrogeophysical approach was developed to reveal the spatial and temporal dynamic flow pathways inside a river corridor as well as the pattern of transient surface water and the groundwater (SW-GW) exchanges. Obtaining such information from traditional hydrological data remains a challenge, both in terms of accuracy and validation. As there is no direct measurement of these fluxes, estimating dynamic pathways and SW-GW exchanges is frequently tackled with the help of numerical models. Yet, the definition of initial and boundary conditions is generally based on poorly constrained assumptions and restrained to the location of piezometers, due to the lack of knowledge of the water table (WT) geometry. We provide a methodology to build stronger constraints to the numerical simulation and the hydrodynamic parameters calibration, both in space and time, by using a multi-method approach. On the Orgeval Critical Zone observatory (France), we show how a thorough interpretation of high-resolution geophysical images, combined with geotechnical data, helps to resolve subsurface structural heterogeneity. This coupling provides a detailed distribution of hydrofacies, valuable prior information about the associated hydrodynamic properties distribution. The temporal dynamic of the WT table can be locally captured with high-resolution time-lapse seismic acquisitions. Time-lapse variations are interpreted as temporal changes in the saturated-unsaturated zone continuum. Each seismic snapshot is then thoroughly inverted to image spatial WT variations. This posterior geophysical information is then used to calibrate the hydrogeological modeling domain. The use of the WT improves the estimation of transient stream-aquifer exchanges, especially during the rain event.