Is the Dupuit assumption suitable for predicting the groundwater seepage area in hillslopes?

Etienne Bresciani, P Davy, J.-R. de Dreuzy

    Research output: Contribution to journalArticle

    10 Citations (Scopus)

    Abstract

    Many physically based hydrological/hydrogeological models used for predicting groundwater seepage areas, including topography-based index models such as TOPMODEL, rely on the Dupuit assumption. To ensure the sound use of these simplified models, knowledge of the conditions under which they provide a reasonable approximation is critical. In this study, a Dupuit solution for the seepage length in hillslope cross sections is tested against a full-depth solution of saturated groundwater flow. In homogeneous hillslopes with horizontal impervious base and constant-slope topography, the comparison reveals that the validity of the Dupuit solution depends not only on the ratio of depth to hillslope length d/L (as might be expected), but also on the ratio of hydraulic conductivity to recharge K/R and on the topographic slope s. The validity of the Dupuit solution is shown to be in fact a unique function of another ratio, the ratio of depth to seepage length d/LS. For d/LS0.2, the relative difference between the two solutions is quite small (<14% for the wide range of parameter values tested), whereas for d/LS0.2, it increases dramatically. In practice, this criterion can be used to test the validity of Dupuit solutions. When d/LS increases beyond that cutoff, the ratio of seepage length to hillslope length L S/L given by the full-depth solution tends toward a nonzero asymptotic value. This asymptotic value is shown to be controlled by (and in many cases equal to) the parameter R/(sK). Generalization of the findings to cases featuring heterogeneity, nonhorizontal impervious base and variable-slope topography is discussed.

    Original languageEnglish
    Pages (from-to)2394-2406
    Number of pages13
    JournalWater Resources Research
    Volume50
    Issue number3
    DOIs
    Publication statusPublished - 2014

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