Ground Penetrating Radar Two-Way Travel Time Sensitivity to Hydrodynamic Parameters During Soil Water Infiltration

Summary In this study, we conducted a variance-based Global Sensitivity Analysis on time-lapse Ground Penetrating Radar synthetic data. We developed a coupled hydrogeological and geophysical model to compute the GPR two-way travel times during a constant head water infiltration in a homogeneous soil with a fixed water table level. We used a large number of random realizations of the model to conduct surrogate modeling based on Polynomial Chaos Expansion method, in order to perform a Global Sensitivity Analysis based on the Sobol indices. The results show the complementarity of the GPR two-way travel times for reflections occurring at the wetting front and at reflectors of fixed depths. The particular focus on the latter evidenced the three hydrodynamic parameters (using the Mualem – van Genuchten model) of the soil with the largest contribution to the total variance of the data : the saturated hydraulic conductivity, the α parameter and the saturated water content.