HR: 0800h
AN: H21D-0746    [Abstracts]
TI: Solving Steady Evaporation-Driven Flow Through a Shallow Aquifer With Piecewise Continuous Forms of Hydraulic Relationships
AU: * Sigda, J M
EM: sigda@nmt.edu
AF: Geomega, 3700 Rio Grande Blvd NW Suite 6, Albuquerque, NM 87110, United States
AU: Wilson, J L
EM: jlwilson@nmt.edu
AF: Department of Earth and Environmental Science, New Mexico Tech, 801 Leroy Place, Socorro, NM 87801, United States
AU: Holt, R M
EM: rmholt@olemiss.edu
AF: Department of Geology and Geological Engineering, University of Mississippi, 118 Carrier Hall, University, MS 38677, United States
AB: Nearly fifty years ago, Wilford Gardner provided analytical solutions to estimate steady evaporation-driven flow from a shallow aquifer. Using analytically tractable functions to describe the relationship between hydraulic conductivity, K, and matric potential, ψ, his solution provides the upward flux and the ψ profile. Though mathematically effective, Gardner's K(ψ) functions typically do not fit field or lab measurements as well as the Mualem-van Genuchten (MvG) or other hydraulic relationships, especially given the large ψ range expected for an evaporation-driven flow system. However, the same large ψ range can cause long run times or non-convergence in the numerical models required to use the MvG relationship. We present a rapid, semi-analytical method based on Gardner's 1958 solution to estimate the evaporation-driven flux through a one-dimensional shallow vadose zone described by the MvG K(ψ) relationship. Like others, piecewise continuous estimates of the MvG K(ψ) relationship are constructed from Gardner's exponential K(ψ) relationship. Unlike other methods, our method provides the unknown evaporation- driven upward flux and the ψ profile across the domain. A system of nonlinear equations is built from the individual Gardner exponential pieces and then solved using Mathematica. The method is rapid, accurate, and can be applied to other K(ψ) relationships. An application to centrifuge-measured hydraulic property data demonstrates the method's utility.
DE: 1818 Evapotranspiration
DE: 1847 Modeling
DE: 1875 Vadose zone
DE: 1894 Instruments and techniques: modeling
SC: Hydrology [H]
MN: 2007 Fall Meeting