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This article in SSSAJ

  1. Vol. 62 No. 5, p. 1185-1190
     
    Received: Oct 10, 1997
    Published: Sept, 1998


    * Corresponding author(s): tssl@cornell.edu
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doi:10.2136/sssaj1998.03615995006200050005x

Preferential Flow in Water-Repellent Sands

  1. Tim W. J. Bauters,
  2. Tammo S. Steenhuis ,
  3. Jean-Yves Parlange and
  4. David A. DiCarlo
  1. Dep. of Agricultural and Biological Engineering, Cornell Univ., Ithaca, NY 14853
    Dep. of Petroleum Engineering, Stanford Univ., Stanford, CA 94305

Abstract

Abstract

Water-repellent soils occur all over the world and affect both groundwater pollution and crop yield. The finger-like wetting patterns in these soils have many similarities with unstable wetting fronts in coarse-grained sandy soils. Our objectives were to study the water movement in water-repellent sand and to examine how the theory for unstable wetting fronts applies to water-repellent sands. Infiltration experiments, in which moisture content and matric potentials were measured, were carried out in slab chambers with identical sands but with different levels of water repellence. Soil water characteristics were determined in separate experiments. Infiltration in the hydrophilic soil resulted in a uniform and horizontal front. All water-repellent sands showed a fingered flow pattern. For negative water-entry values, water infiltrated without delay. For positive values, water entered the soil only after the depth of the ponded water equaled or exceeded the water-entry pressure, which increased with increasing repellency. The finger widths predicted with the unstable flow theory agreed rather well with the observed values. In general, the research showed that the wetting patterns of water-repellent sands depended directly on the soil water characteristic curve. This implies that the type of wetting front and risk to groundwater pollution can be predicted based on laboratory-measured soil hydraulic properties.

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