Incorporating Petrophysical Variability to Coupled Hydrogeophysical Modelling of DC Resistivity in Heterogeneous Coastal Aquifers

Geophysical techniques are well suited to provide additional data for the parametrization of groundwater models. Joint use of geophysical and hydrological information through coupled modelling and inversion relies in an appropriate transfer function, the petrophysical model. Due to uncertainties in the spatial distribution of petrophysical model parameters, constant distributions are often used as a simplifying assumption, even when heterogeneity is present in the subsurface. When using this simplification, discrepancies can arise in the computed geophysical response. In this work, we show how spatially variable properties and simultaneous petrophysical models can be utilized in a coupled hydrogeophysical modelling. The developed coupled modelling relies in the definition of adequate transfer functions between models (hydrological and geophysical), providing direct correspondence between the spatial distribution of the hydrogeological and electrical properties. It has been observed that the effects of lithological heterogeneity can have as much importance as fluid salinity variations only. Therefore, when assuming constant petrophysical parameterizations geophysical results might be interpreted incorrectly. The understanding of these effects is a necessary step for a correct application of the petrophysical model in hydrogeophysical studies and shows the importance of petrophysical parameter variability when using coupled modelling methodologies for accurate imaging and quantification of saltwater intrusion.