Hydrogeophysical characterization and determination of petrophysical and hydrodynamic parameters at the O-ZNS observatory of the vadose zone.
Abstract
The vadose zone is a major concern in the field of environmental science, as it is a critical medium that controls the transfer of water and contaminants from the surface to the groundwater. Therefore, detailed characterization of the vadose zone structure, and its key physicochemical processes with their multilevel coupling is of utmost importance in predicting the fate of solutes including contaminants. In this context, the "Observatory of Transfers in the Vadose Zone" (O-ZNS) project is focused on developing a hydrogeophysical approach capable of characterizing the vadose zone by providing physical, biogeochemical and spatially resolved hydraulic parameters that can characterize flow patterns and parameterize transport models (Binley et al., 2015; Sassen et al., 2012). The O-ZNS observatory presents an exceptional experimental setup, located in Villamblain (France), and composed of a main well having a depth of 20 m and a diameter of 4 m along with several surrounding instrumented boreholes and piezometers (Figure 1a). This study aims to characterize the heterogeneities of the carbonate vadose zone and to obtain different petrophysical parameters by combining surface and cross-hole electrical resistivity and ground penetrating radar (GPR) data with geomechanical and hydrogeological measurements (Aldana et al., 2020; Mallet et al., 2021). Additionally, high-resolution 3D GPR and water content measurements were carried out in parallel to the main well drilling in order to extend our study to a high-resolution 3D scale. Achieving an efficient determination of site-specific petrophysical parameters is expected to provide a reliable water saturation estimation and derived transport parameters prediction by reducing uncertainties associated with using literature values. The efficiency of this approach was evaluated by comparing the results with those obtained from laboratory and hydrological models. Uncertainty analyses were carried out for each method in order to assess the impact of petrophysical parameters on the water saturation values. Our primary results showed a strong correlation between geophysical, hydrogeological and geotechnical data and highlighted the presence of heterogeneities that can have profound effects on the vadose zone transport dynamics.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2021
- Bibcode:
- 2021AGUFMNS35B0366A