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Journal of Environmental Quality Abstract - Vadose Zone Processes and Chemical Transport

Impact of Preferential Flow at Varying Irrigation Rates by Quantifying Mass Fluxes


This article in JEQ

  1. Vol. 33 No. 3, p. 1033-1040
    Received: July 1, 2002

    * Corresponding author(s): tgish@hydrolab.arsusda.gov
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  1. T. J. Gish *a,
  2. K.-J. S. Kungc,
  3. D. C. Perrye,
  4. J. Posnerc,
  5. G. Bubenzerd,
  6. C. S. Hellingb,
  7. E. J. Kladivkof and
  8. T. S. Steenhuisg
  1. a Hydrology and Remote Sensing Laboratory, USDA-ARS, BARC-West, 10300 Baltimore Boulevard, Beltsville, MD 20705-2350
    c Agronomy Department, University of Wisconsin, Madison, WI 53706-1299
    e Civil Engineering Department, Santa Clara University, 500 Camino Real, Santa Clara, CA 95053
    d Department of Biological System Engineering, University of Wisconsin, Madison, WI 53706-1299
    b Alternate Crops and Systems Laboratory, USDA-ARS, BARC-West, 10300 Baltimore Boulevard, Beltsville, MD 20705-2350
    f Department of Agronomy, Purdue University, West Lafayette, IN 47906
    g Department of Agricultural and Biological Engineering, Cornell University, Ithaca, NY 14853


Solute concentration and soluble dye studies inferring that preferential flow accelerates field-scale contaminant transport are common but flux measurements quantifying its impact are essentially nonexistent. A tile-drain facility was used to determine the influence of matrix and preferential flow processes on the flux of mobile tracers subjected to different irrigation regimes (4.4 and 0.89 mm h−1) in a silt loam soil. After tile outflow reached steady state either bromide (Br; 280 kg ha−1) or pentafluorobenzoic acid (PFBA; 121 kg ha−1) was applied through the irrigation system inside a shed (3.5 × 24 m). Bromide fluxes were monitored at an irrigation rate of 4.4 mm h−1 while PFBA fluxes were monitored at an irrigation rate of 0.89 mm h−1 At 4.4 mm h−1 nearly one-third of the surface-applied Br was recovered in the tile line after only 124 mm of irrigation and was poorly fit by the one-dimensional convective–dispersive equation (CDE). On the other hand, the one-dimensional CDE fit the main PFBA breakthrough pattern almost perfectly, suggesting the PFBA transport was dominated by matrix flow. Furthermore, after 225 mm of water had been applied, less than 2% of the applied PFBA had been leached through the soil compared with more than 59% of the applied Br. This study demonstrates that the methodology of applying a narrow strip of chemical to a tile drain facility is appropriate for quantifying chemical fluxes at the small-field scale and also suggests that there may be a critical input flux whereby preferential flow is initiated.

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