Hydraulic conductivity of stratified unsaturated soils: Effects of random variability and layering

Mohammad R. Gohardoust, Morteza Sadeghi, Mirkhalegh Ziatabar Ahmadi, Scott B. Jones, Markus Tuller

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


For simulating flow in heterogeneous porous media it is computationally more efficient to define an equivalent effective (i.e., upscaled) medium rather than considering detailed spatial heterogeneities. In this paper, the effective unsaturated hydraulic conductivity (K) of soils exhibiting random variability, layering, or both is calculated based on numerical simulations of steady-state evaporation from a shallow water table. It is demonstrated that the effective K of randomly-varied coarse-textured soils generally falls between the harmonic and geometric means of the unsaturated hydraulic conductivities of the constituting soils. Layering and random variability when occurring concurrently magnify each other's effects on effective K. As a result, the higher the degree of heterogeneity, the lower the effective K. Therefore, neglecting either random spatial variability or layering in numerical simulations can lead to significant overestimation of water flow in soils.

Original languageEnglish (US)
Pages (from-to)81-89
Number of pages9
JournalJournal of Hydrology
StatePublished - Mar 1 2017
Externally publishedYes

Bibliographical note

Funding Information:
The authors gratefully acknowledge support from the National Science Foundation (NSF) through Grant No. 1521469, awarded to Utah State University and the University of Arizona, and from the Arizona Agricultural Experiment Station (AAES).

Publisher Copyright:
© 2016 Elsevier B.V.


  • Effective unsaturated hydraulic conductivity
  • Random variability
  • Soil layering
  • Steady state evaporation
  • Upscaling


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