Soil hydrodynamic parameter determination using Ground-Penetrating Radar monitoring

Abstract:

Soil hydraulic properties, represented by the soil water retention and
hydraulic conductivity functions, dictate water flow in the vadose
zone, from surface to aquifers. Understanding the water flow dynamic
has important implications for estimating available water resources
and flood forecasting. It is also crucial in evaluating the dynamics
of chemical pollutants in soil and in assessing the risks of
groundwater pollution. Ground Penetrating Radar is a geophysical
method particularly suited to measure contrasts of electromagnetic
parameters such as those created by water content variations in soils.
We developed coupled hydrodynamic and electromagnetic numerical
modeling to invert the two way travel times associated with
reflections corresponding to strong dielectric permittivity contrasts
such as wetting front and wetting bulb.

We will present three different techniques using Ground Penetrating
Radar monitoring: one using a single ring infiltrometer, an other one
using shallow boreholes and the last one being a laboratory large
cylindrical tank in which we applied different water table levels.

We used the parametrical Mualem-van Genuchten model to fit soil-water
retention and hydraulic conductivity functions. Using Ground
Penetrating Radar data inversion, we optimized the Mualem-van
Genuchten parameters using Shuffled Complex Evolution algorithm.

Results are compared with classical laboratory and field methods.