Saturated hydraulic conductivity determined by on ground mono-offset Ground-Penetrating Radar inside a single ring infiltrometer

TL;DR

This paper introduces a novel method using Ground-Penetrating Radar (GPR) data and hydrological modeling to non-invasively determine saturated hydraulic conductivity during water infiltration in soils, validated through synthetic and real experiments.

Contribution

It presents a new approach combining GPR data, water infiltration modeling, and dielectric permittivity conversion to invert saturated hydraulic conductivity.

Findings

Method successfully retrieves hydraulic conductivity in synthetic tests.

Application to real sand soil experiments demonstrates practical viability.

Uncertainty analysis highlights factors affecting inversion accuracy.

Abstract

In this study we show how to use GPR data acquired along the infiltration of water inside a single ring infiltrometer to inverse the saturated hydraulic conductivity. We used Hydrus-1D to simulate the water infiltration. We generated water content profiles at each time step of infiltration, based on a particular value of the saturated hydraulic conductivity, knowing the other van Genuchten parameters. Water content profiles were converted to dielectric permittivity profiles using the Complex Refractive Index Method relation. We then used the GprMax suite of programs to generate radargrams and to follow the wetting front using arrival time of electromagnetic waves recorded by a Ground-Penetrating Radar (GPR). Theoretically, the 1D time convolution between reflectivity and GPR signal at any infiltration time step is related to the peak of the reflected amplitude recorded in the corresponding trace in the radargram. We used this relation ship to invert the saturated hydraulic conductivity for constant and falling head infiltrations. We present our method on synthetic examples and on two experiments carried out on sand soil. We further discuss on the uncertainties on the retrieved saturated hydraulic conductivity computed by our algorithm from the van Genuchten parameters.