Examination of the potential for time domain electromagnetic method for monitoring infiltration and recharge in arid areas

Abstract EN

Recharge flux is one of the most difficult components of the water balance to measure.

However, quantitative estimates of this flux are critical for water resource planning in semi-arid and arid areas.

Geophysical methods that can be operated from the ground surface offer significant advantages for recharge monitoring.

Specifically, because they do not require boreholes, they are typically inexpensive and can be used to monitor over large areas.

Electrical and electromagnetic geophysical methods may be useful for monitoring recharge because of the dependence of both the electrical conductivity and the dielectric permittivity on the volumetric water content of a porous medium.

However, it is unclear whether the pattern of water content change that occurs during recharge can be inferred, uniquely, from all geophysical responses.

In this study, we examine the suitability of time domain electromagnetic (TEM) methods for monitoring infiltration into an initially dry soil.

This preliminary examination is conducted as a sensitivity analysis in which we vary the porosity (P), initial water content (Wci) and the hydraulic conductivity (K) of the medium and calculate the TEM response with time during an infiltration event.

Infiltration into a dry medium causes a large, localized change in the water content, making these conditions most conducive to recharge monitoring with geophysical methods.

We consider this study to be a firstlevel examination of the potential for recharge monitoring with TEM.