On the electrical-hydraulic conductivity correlation in aquifers

Abstract

As a justification for the geoelectric characterization of the hydraulic conductivity field, this paper shows theoretically and empirically that electrical and hydraulic (eh) conductivities of aquifers can be correlated. The correlation, demonstrated at the microscale by a published network model of eh transport, arises from the fact that both the conductivities are a function of connected pore volumes and connected pore surface areas. By considering skewed pore size distributions the microscale equations of eh conductivity scale up to power laws of porosity and specific surface area similar to Archie's law and the Kozeny equation. Also, a third, apparently unreported Archie-type power law relating electrical conductivity to specific surface area and the cation exchange phenomenon is predicted theoretically and confirmed experimentally. These equations imply a simple log-log linear correlation between eh conductivities that is either positive or negative. The positive correlation corresponds to a pore-volume-dominated electrical flow environment and the negative correlation corresponds to a pore-surface-dominated electrical flow environment. These relationships are supported by many published laboratory and field investigations cited in the paper.