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This article in SSSAJ

  1. Vol. 74 No. 5, p. 1469-1482
    Received: Feb 11, 2010

    * Corresponding author(s): laj.ahuja@ars.usda.gov
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Effective Soil Properties of Heterogeneous Areas For Modeling Infiltration and Redistribution

  1. L.R. Ahuja *,
  2. L. Ma and
  3. T.R. Green
  1. USDA-ARS, Agricultural Systems Research Unit, 2150 Centre Ave, Bldg. D, Fort Collins, CO 80526


Field-scale infiltration, soil water, and solute transport models require spatially averaged “effective” soil hydraulic parameters to represent the average flux and storage. The values of these effective parameters vary for different conditions and processes. The objective of this study was to explore some effective parameter sets to describe field-average infiltration and redistribution under different rainfall conditions. We investigated whether an effective field saturated hydraulic conductivity, K s,eff, and correlated hydraulic parameters derived from matching early-stage average ponded infiltration could give reasonable results for infiltration under lower rainfall rates as well as for soil water redistribution. The results of this Effective Parameter Set 1 (EPS-1) were compared with those of two other parameter sets: EPS-2, where the same K s,eff was combined with other hydraulic parameters that were arithmetic mean values of the component soils in the field; and EPS-3, where all parameters were arithmetic mean values. The RZWQM2 model was used to explore these objectives for five different cases of a heterogeneous field, comparing results from effective properties with weighted mean values of component soils at four different rainfall intensities. The mean absolute error for infiltration generally increased with decreasing rain intensity but were generally least with EPS-1 and greatest with EPS-3. The EPS-1 gave good results for infiltration up to 4 h; however, it gave poor results for the mean soil water content distributions 7 d after infiltration. The EPS-2 gave reasonable results for both cumulative infiltration and soil water redistribution. The study confirms that an optimal EPS must strike a balance between infiltration and redistribution. For infiltration, computing K s,eff was critical, and this needed to be combined with mean values of water retention parameters for redistribution.

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