Combined electrical resistivity and pumping test modelling

Contaminant transport issues, coupled with advanced numerical modelling techniques have led to an increased demand for quantitative descriptions of groundwater systems. To determine the distribution of hydraulic parameters, resistivity techniques have been employed to complement conventional hydraulic tests. The electrical resistivity of a saturated rock or sediment is a function of the porosity, the electrical resistivity of the saturating fluid, the resistivity of the solid rock or sediment. the surface conductance of the rock or soil and the tortuosity of the electrical and fluid path. It is generally assumed that for most formations with low c1ay content the electrical current is conducted electrolytically through the pore waters (Urish, 1981). This has led to numerous attempts to define a relationship between electrical resistivity and hydraulic conductivity. However, both direct and inverse relationships have been reported, thus highlighting the dominanee of surface conductance effects and the problerns incurred by neglecting its importance (Huntley, 1986).