HESS Hydrology and Earth System Sciences HESS Hydrol. Earth Syst. Sci. 1607-7938 Copernicus Publications Göttingen, Germany 10.5194/hess-17-611-2013 Identifying a parameterisation of the soil water retention curve from on-ground GPR measurements Dagenbach A. 1 Buchner J. S. 1 Klenk P. 1 Roth K. https://orcid.org/0000-0003-2634-8825 1 Institute of Environmental Physics, Heidelberg University, Heidelberg, Germany 11 02 2013 17 2 611 618 Copyright: © 2013 A. Dagenbach et al. 2013 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://hess.copernicus.org/articles/17/611/2013/hess-17-611-2013.html The full text article is available as a PDF file from https://hess.copernicus.org/articles/17/611/2013/hess-17-611-2013.pdf

We show the potential of on-ground Ground-Penetrating 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 <i>m</i> = 1 − 1/<i>n</i> 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 <i>m</i> = 1 − 1/<i>n</i>.

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