Abstract.We show the potential of on-ground GroundPenetrating Radar (GPR) to identify the parameterisation of the soil water retention curve, i.e. its functional form, with a semi-quantitative analysis based on numerical simulations of the radar signal. An imbibition and drainage experiment has been conducted at the ASSESS-GPR site to establish a fluctuating water table, while an on-ground GPR antenna recorded traces over time at a fixed location. These measurements allow to identify and track the capillary fringe in the soil. The typical dynamics of soil water content with a transient water table can be deduced from the recorded radargrams. The characteristic reflections from the capillary fringes in model soils that are described by commonly used hydraulic parameterisations are investigated by numerical simulations. The parameterisations used are (i) full van Genuchten, (ii) simplified van Genuchten with m = 1 − 1 n and (iii) Brooks-Corey. All three yield characteristically different reflections, which allows the identification of an appropriate parameterisation by comparing to the measured signals. We show that for the sand used here, these signals are not consistent with the commonly used simplified van Genuchten parameterisation with m = 1 − 1 n .

Please find the reply to the anonymous referee #2 attached as supplement and note that a revised version of the manuscript has been uploaded as a separate author comment. Please also note the supplement to this comment: https://www.hydrol-earth-syst-sci-discuss.net/hess-2017-538/hess-2017-538-AC2-supplement.pdf Interactive comment on Hydrol. Earth Syst. Sci. Discuss., https://doi.

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