Barometric pressure variation alters electrical resistivity during water infiltration in the vadose zone

Abstract

To reveal the mechanism of the water–gas two-phase repulsion during water infiltration and its barometric pressure change and resistivity response in the vadose zone while it provides the basic theory for water resources evaluation and groundwater pollution, also provides technical support for the accurate interpretation of electrical resistivity tomography (ERT) application. Therefore, a research system based on laboratory experiments, numerical simulations, and ERT was established to determine the moisture transport pattern and the quantitative relationships between barometric pressure and resistivity. The results show that the intensity of the water infiltration process in the vadose zone meets the percolation theory. The barometric pressure will go through three stages when the infiltration intensity is higher than the critical value. The critical time of the barometric pressure variation shortens gradually with the infiltration intensity and medium permeability increase. In contrast, the maximum barometric pressure increases gradually with the rise in infiltration intensity and medium porosity. The layered-heterogeneous structure's effect depends on the underlying medium's properties. The trivial variation of resistivity responds to the barometric pressure variation. The quantitative relationship between the resistivity and the barometric pressure in the vadose zone is established by the difference between the measured value and the calculated value by improving Archie's formula. The resistivity reduction due to increasing barometric pressure can account for over 10.9% of the moisture effect. These insights provide technical support for ERT applications to eliminate barometric pressure's effect on resistivity and accurately identify the target medium.