Can electrical conductivity data from a single pumping test provide information about the location of a neighboring mixing zone between two aquifers? An example from Aix-les-Bains/Marlioz (Savoie, France)

Pumping tests were first developed to interpret observed drawdown in wells. Analyses of drawdown and temperature profiles now help petroleum geologists and geothermal-energy specialists improve production rates, and numerous hydrogeological studies have combined drawdown data with measures of electrical conductivity or a chemical parameter (often a pollutant). The present study used electrical conductivity data from a pumping test in a single well to obtain information about the position of the hydrothermal plume that feeds Aix-les-Bains’ Thermes de Marlioz spa. Applying this data to a 3D model of an equivalent porous medium showed that the plume at the bottom of the subsurface aquifer must be downstream from the well. In the present study, combining drawdown data for a single well with electrical-conductivity measurements provided an efficient method for determining the position of a mixing zone near pumped wells. This method may well be generalizable to other situations.