Time-lapse geophysics for monitoring an infiltration test in the vadose zone

The flow condition in the vadose zone was monitored by taking measurements of the electromagnetic properties of the subsoil (electrical conductivity and permittivity) to estimate the spatial distribution of the volumetric water content. A controlled experiment of 4x1 m2 of pond infiltration was designed and done in a sandy soil; the time-lapse electrical resistivity tomography (TLERT) was integrated by Time Domain Reflectometry (TDR) electromagnetic monitoring to analyze variations of water content. The results permitted us to estimate the water-content distribution up to a 2m depth with accurate lateral detail; because of the duration of the experiments (85 days), several rainfall events modified the water contents of the subsoil: however, the combined approach (TDR and TLERT) permitted us to recognize the different water-content conditions in the zone of artificial infiltration. The interpretation of the experiment has been realised combining the geophysical interpretation and the results of a 2-D simulation of the flow in an unsaturated zone using numerical models.