Abstract
This chapter describes a series of detailed soil-water tracer experiments conducted in a natural landscape. It also discusses three different approaches taken to numerically model the observed flow and transport. These field experiments provide the first conclusive evidence for the existence of a variable, state-dependent anisotropy in the hydraulic conductivity of an unsaturated, layered medium in a natural field setting. This concept has been previously postulated in a number of independent theoretical and experimental investigations. While previous studies have identified layered heterogeneity as the principal cause of state-dependent anisotropy, we develop a simple scenario to show how hysteresis in the soil-moisture characteristics (θ-ψ relationship) can contribute to the anisotropic behavior of a texturally homogeneous, porous media profile under transient, unsaturated conditions. Three approaches at modeling the observed flow and transport are implemented and compared. The results of the computer simulations indicate that even relatively uniform media (such as the sands from our field site) exhibit variable anisotropy, and that local (laboratory scale) hysteresis makes only minor contributions to macroscopic anisotropic flow behavior.
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© 1991 Springer Science+Business Media Dordrecht
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McCord, J.T., Stephens, D.B., Wilson, J.L. (1991). Numerical Simulations and Field Experiments of Unsaturated Flow and Transport: The Roles of Hysteresis and State-Dependent Anisotropy. In: Bowles, D.S., O’Connell, P.E. (eds) Recent Advances in the Modeling of Hydrologic Systems. NATO ASI Series, vol 345. Springer, Dordrecht. https://doi.org/10.1007/978-94-011-3480-4_29
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DOI: https://doi.org/10.1007/978-94-011-3480-4_29
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