Estimating Water Content of Soils from Electrical Resistivity

Electrical resistivity has been demonstrated to be an effective predictor of various soil hydraulic properties including water content, degree of saturation, and hydraulic conductivity. Standardized laboratory procedures for measuring soil electrical resistivity are based on the use of the Miller soil box for determining soil corrosive potential from soil resistivity. However, these procedures and the Miller soil box do not allow for the flexibility in measurements necessary to develop explicit relationships between soil resistivity and hydraulic properties. As an alternative to the use of the Miller soil box, circular four-probe resistivity cells provide a measurement method that can be used to develop explicit relationships between soil resistivity and hydraulic parameters. For a test experiment, relationships were developed where volumetric water content could be estimated from soil resistivity with a standard error of 0.009.