Time-Lapse ERT, Moment Analysis, and Numerical Modeling for Estimating the Hydraulic Conductivity of Unsaturated Rock

In recent years, geophysical techniques have been increasingly used to monitor flow andtransport processes in the Earth critical zone (ECZ). Among these, electrical resistivity tomography(ERT) is a powerful tool used to predict hydrological parameters and state variables that influencethe mentioned processes in the vadose zone because of the strong correlation between electricaland hydrological properties of the filtering medium. There have been many field tests consideringgeophysical prospecting in soils, where point scale hydrological sensors measurements are typicallycollected through sensors for geophysical data validation; on the contrary, when the unsaturatedzone is made of hard rocks, the installation of such sensors is not a trivial issue owing to the extremedifficulties to guarantee contact between sensors and the surrounding medium. In this context,the geophysical data combined with appropriate numerical analysis techniques can effectivelyovercome the lack of information of the unsaturated subsurface, which is otherwise unpredictablewith traditional methods. In the proposed case study, hydrogeophysical data were collected toprovide a quantitative estimation of the hydraulic conductivity of sandstone through an integratedapproach based on the moment analysis technique and numerical modeling.