Estimation of Hydraulic Conductivity in a Large Scale Laboratory Model by Means of the Self- Potential Method

The characterization of a heterogeneous aquifer involves a wide spectrum of high resolution direct measurements of the characteristic parameters, defined in itinere according to the various approaches used. This information is usually obtained from the pumping tests and the relative measurements of the drawdown induced. Unfortunately, these methods are intrusive and the hydrological system is perturbed by the presence of perforations. An aim of geophysics is to use non-intrusive techniques obtaining a great deal of information on subsoil at low cost. In this article a novel methodology to estimate the hydraulic conductivity from selfpotential measurements is proposed. The hydrogeophysical experiments were carried out in the CNR-IMAA (Marsico Nuovo Italy) Hydrogeosite Laboratory, a large scale model sized 10  7  3 m, filled with a homogeneous medium made up of a quartzrich sand with a medium-high hydraulic conductivity in the order of 10 m/s. Self-potential signals generated by the groundwater flow, during a pumping test, were measured on the ground surface, both on pumping and recovery phases. Firstly, hydraulic conductivity was calculated by means of Neuman Type-Curves method applied on the pumping test. As a result, hydraulic conductivity very close to that calculated from hydraulic data, by means of Neuman Type-Curves, has been obtained by solving numerically the electrical flow equation.