Plausibility of freshwater lenses adjacent to gaining rivers: Validation by laboratory experimentation

Adrian Werner, A. Kawachi, Tariq Laattoe

    Research output: Contribution to journalArticlepeer-review

    8 Citations (Scopus)


    The occurrence of freshwater lenses in saline aquifers adjoining gaining rivers has recently been demonstrated as being theoretically possible by way of analytical solution. However, physical evidence for freshwater lenses near gaining rivers is limited largely to airborne geophysical surveys. This paper presents the first direct observations of freshwater lenses adjacent to gaining rivers, albeit at the laboratory-scale, as validation of their plausibility. The experimental conditions are consistent with the available analytical solution, which is compared with laboratory observations of lens extent and the saltwater flow rate, for various hydraulic gradients. Numerical simulation shows that dispersion can account for the small amount of mismatch between the sharp-interface analytical solution and laboratory measurements. Calibration and uncertainty analysis demonstrate that accurate mathematical predictions require calibration to laboratory measurements of the lens. The results provide unequivocal proof that freshwater lenses can persist despite gaining river conditions concordant with theoretical lenses predicted by the analytical solution, at least within the constraints of the experimental setup.

    Original languageEnglish
    Pages (from-to)8487-8499
    Number of pages13
    JournalWater Resources Research
    Issue number11
    Publication statusPublished - 1 Nov 2016


    • analytical solution
    • freshwater lens
    • physical model
    • sand tank
    • variable-density flow


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