Fully Coupled Hydrogeophysical Inversion of Salt Tracer Experiments Monitored by Electrical Resistivity Tomography

Geophysical techniques have been used in various studies to monitor hydraulic experiments in order to obtain information about hydraulic conductivity. One of these methods is the use of electrical resistivity tomography during salt tracer tests. We use an approach in which the hydraulic conductivity distribution is directly related to the electrical potential differences measured during the experiments. This approach, which considers geoelectrics and hydraulics in a coupled way in order to avoid non-physical results, makes use of temporal moments of electrical potential perturbations. The latter can be computed by moment generating equations. We consider as measurements the ratio of the first over the zeroth moment, indicating the mean arrival time of the perturbation. In addition to that, also some head measurements are included. For inversion, the quasi-linear geostatistical approach is used. We apply the method to a two-dimensional synthetic case study, and compare the obtained hydraulic conductivity field and transient behaviour with the true conditions. The results show generally a reasonable agreement between the true and estimated field and also between the actual and estimated plume propagation within the domain.