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Estimating vadose zone hydraulic properties using ground penetrating radar:the impact of prior information

Scholer, Marie and Irving, James and Binley, Andrew and Holliger, Klaus (2011) Estimating vadose zone hydraulic properties using ground penetrating radar:the impact of prior information. Water Resources Research, 47 (10). ISSN 0043-1397

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    Abstract

    A number of geophysical methods, such as ground-penetrating radar (GPR), have the potential to provide valuable information on hydrological properties in the unsaturated zone. In particular, the stochastic inversion of such data within a coupled geophysical-hydrological framework may allow for the effective estimation of vadose zone hydraulic parameters and their corresponding uncertainties. A critical issue in stochastic inversion is choosing prior parameter probability distributions from which potential model configurations are drawn and tested against observed data. A well chosen prior should reflect as honestly as possible the initial state of knowledge regarding the parameters and be neither overly specific nor too conservative. In a Bayesian context, combining the prior with available data yields a posterior state of knowledge about the parameters, which can then be used statistically for predictions and risk assessment. Here we investigate the influence of prior information regarding the van Genuchten-Mualem (VGM) parameters, which describe vadose zone hydraulic properties, on the stochastic inversion of crosshole GPR data collected under steady state, natural-loading conditions. We do this using a Bayesian Markov chain Monte Carlo (MCMC) inversion approach, considering first noninformative uniform prior distributions and then more informative priors derived from soil property databases. For the informative priors, we further explore the effect of including information regarding parameter correlation. Analysis of both synthetic and field data indicates that the geophysical data alone contain valuable information regarding the VGM parameters. However, significantly better results are obtained when we combine these data with a realistic, informative prior.

    Item Type: Article
    Journal or Publication Title: Water Resources Research
    Additional Information: Copyright 2011 by the American Geophysical Union.
    Uncontrolled Keywords: TIME-DOMAIN REFLECTOMETRY ; CONDUCTIVITY ; BOREHOLE GEOPHYSICAL METHODS ; DISTRIBUTIONS ; MODEL ; SOIL-WATER CONTENT ; PARAMETERS ; FLOW ; UNSATURATED SANDSTONE ; UNCERTAINTY ; GPR ; MCMC ; prior information ; stochastic inversion ; vadose zone
    Subjects: UNSPECIFIED
    Departments: Faculty of Science and Technology > Lancaster Environment Centre
    ID Code: 58288
    Deposited By: ep_importer_pure
    Deposited On: 19 Sep 2012 10:51
    Refereed?: Yes
    Published?: Published
    Last Modified: 14 Mar 2014 10:21
    Identification Number:
    URI: http://eprints.lancs.ac.uk/id/eprint/58288

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