Remote Estimation of the Hydraulic Properties of a Sand Using Full‐Waveform Integrated Hydrogeophysical Inversion of Time‐Lapse, Off‐Ground GPR Data

Abstract

S S : A I We used integrated hydrogeophysical inversion of me-lapse, proximal ground penetra ng radar (GPR) data to remotely infer the unsaturated soil hydraulic proper es of a laboratory sand during an infi ltra on event. The inversion procedure involved full-waveform modeling of the radar signal and one-dimensional, ver cal fl ow modeling. We combined the radar model with HYDRUS-1D. The radar system was set up using standard, handheld vector network analyzer technology. Signifi cant eff ects of water dynamics were observed on the me-lapse radar data. The es mated hydraulic parameters were rela vely consistent with direct characteriza on of undisturbed sand samples. Signifi cant diff erences were par cularly observed for the saturated hydraulic conduc vity, which was underes mated by two orders of magnitude. Nevertheless, the use of soil hydraulic parameters derived from reference measurements failed to correctly predict water dynamics, whereas GPR-based predic ons captured some of the major features of me domain refl ectometry measurements and be er agreed with visual observa ons. These results suggest that the proposed method is promising for noninvasive, eff ec ve hydraulic characteriza on of the shallow subsurface and hence, monitoring of water dynamics at the fi eld scale.

Method of Relating Grain Size Distribution to Hydraulic Conductivity in Dune Sands to Assist in Assessing Managed Aquifer Recharge Projects: Wadi Khulays Dune Field, Western Saudi Arabia

“…Hence, we used the shuffled complex evolution (SCE-UA) algorithm for the global optimization. This global optimization algorithm has been widely used in hydrologic modeling [34], and proved to be consistent and efficient for finding the global optimum parameter values of integrated hydrogeophysical and hydrologic models [35,36].…”

Soil hydraulic material properties and layered architecture from time-lapse GPR

“…They have the disadvantage, however, that the antenna characteristics are influenced by the coupling to the ground. Off-ground measurements (e.g., Lambot et al, 2009;Jadoon et al, 2012;Jonard et al, 2015) avoid these effects, but the measurements are influenced by surface roughness. Cross-borehole measurements allow for high-resolution tomography of the subsurface (e.g., Ernst et al, 2007;Looms et al, 2008;Scholer et al, 2011) but require boreholes which are destructive and expensive.…”

“…Ray tracing (Léger et al, 2014(Léger et al, , 2015 is fast but merely yields an approximate solution of Maxwell's equations. These equations can be solved analytically with Green's function (e.g., Lambot et al, 2009;Busch et al, 2012;Jonard et al, 2015) assuming a layered subsurface architecture. Alternatively, Maxwell's equations can be solved numerically with the finite differences time domain (FDTD) method (e.g., Taflove and Hagness, 2000).…”

“…Many full waveform inversion approaches directly use the resulting Green's function (e.g., Lambot et al, 2009;Busch et al, 2012;Jadoon et al, 2012) in the cost function. Using the full antenna signal may lead to many local minima prohibiting a reliable identification of the global minimum (e.g., Bradford et al, 2014).…”

Soil hydraulic material properties and subsurface architecture from time-lapse GPR

“…Many full waveform inversion approaches directly use the resulting Green's function (e.g., Lambot et al, 2009;Busch et al, 2012;Jadoon et al, 2012) in the cost function. Using the full antenna signal may lead to many local minima prohibiting a reliable identification of the global minimum (e.g., ford et al, 2014).…”