Estimating soil hydraulic conductivity from time-lapse ground-penetrating radar data in podzolic soils using the green-ampt model

Efficient soil water management and prediction of contaminant transport requires a deep understanding of spatial and temporal variation in soil hydraulic properties (SHPs). The growing interest in using ground-penetrating radar (GPR) for large-scale and non-destructive estimation of SHPs demands more effective approaches. This study evaluates the potential for monitoring soil water content (SWC) changes and estimating field-saturated hydraulic conductivity (K_fs) by employing the Green-Ampt (GA) model using GPR time-lapse data. At two locations at a podzolic soil site in western Newfoundland, Canada, infiltration experiments were carried out on different days using the Beerkan method, which involved applying equal volumes of water over a short duration. A surface GPR system with a center frequency of 500 MHz was employed to monitor these experiments. The downward movement of the wetting zone during infiltration was monitored by collecting time-lapse GPR traces every 5 s. SWC changes estimated from GPR (GPR-SWC), and soil moisture probes (SMP-SWC) (installed to a depth of 0.20 m) were used as parameters in the GA model to estimate K_fs. Our findings show that GPR provided consistent information on the dielectric constant (r = 0.902) and SWC variations during the infiltration experiment at both locations. The average K_fs value (1.4 × 10^-5 ± 5.4 × 10^-6 m/s) estimated using the GPR-SWC in the GA model was in a similar magnitude to the theoretical value for the tested soil type and in close range to values measured by using conventional methods, although all approaches were significantly different. Further research is needed to validate this approach across various soil types and conditions.