  In this study we used Hydrus-1D to simulate water infiltration from a ring
infiltrometer. We generated water content profiles at each time step of
infiltration, based on a particular value of the saturated hydraulic
conductivity while 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 depth of the inflection point of the water content profile
simulated 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
relationship 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. We further discuss the possibility of
estimating two other van Genuchten parameters, n and \alpha, in addition to the
saturated hydraulic conductivity.
