Study of Water Transfer Dynamics in a Carbonate Vadose Zone from Geophysical Properties

Abstract : This paper reports a study of water dynamics in a carbonate vadose zone (VZ). This study is performed in the experimental natural site of Saint-Emilion located in an underground quarry (Gironde, France). For this, two geophysical properties are used: the time domain reflectometry method (TDR) which provides the volumetric water content and electrical properties which provides the spatial water distribution. The dephasing and amplitude attenuation of the water content front were measured and modelled. Physical properties of the porous medium (porosity, permeability and effective diffusivity) can explain the water transfer process in VZ. The electrical resistivity tomography (ERT) gives a series of 2D images of water dynamics in VZ. Variations in water content induce changes in the electrical properties of the medium such as electrical resistivity. Using the time-lapse method, it is possible to model the evolution of saturation over time. The reliability of these electrical tools was confirmed by laboratory measurements.