HR: 08:30h
AN: H41B-03    [Abstracts]
TI: Combined Macroscopic Invasion Percolation and Continuum Modeling of Electrical Resistivity Measurements in Unsaturated Media
AU: * Holt, R M
EM: rmholt@olemiss.edu
AF: University of Mississippi, Dept of Geol. and Geol Eng. 118 Carrier Hall, University, MS 38677, United States
AB: When coupled with unsaturated flow models, electrical resistivity techniques (including tomography) offer the promise of non-intrusive characterization of moisture within the unsaturated zone. Most unsaturated flow models (e.g., Richards' equation) are continuum models that are incapable of reproducing the complicated aqueous- phase structure observed in many field and laboratory experiments. This heterogeneous distribution of moisture contributes to highly heterogeneous distributions of electrical conductivity (EC) within unsaturated materials. We explore the influence of this heterogeneity using an experimentally verified modeling study. We simulate the evolution of aqueous phase structures using a macroscopic invasion percolation (MIP) model that accurately reproduces the complicated aqueous phase structures that arise within unsaturated porous media. Unlike traditional invasion percolation (IP) models which specify individual pore throats and necks, MIP models use an up-scaled blocks that are defined by a local threshold spanning (capillary) pressure. Block moisture contents are then mapped to block-specific EC values using the constitutive model of Mualem and Friedman (1991). Resulting heterogeneous EC fields are then used in a finite-difference model to simulate resistivity measurements. This approach is experimentally verified by simulations of laboratory measurements of electrical resistivity in layered samples at various moisture contents. Broader implications are explored through additional simulations.
DE: 1866 Soil moisture
DE: 1875 Vadose zone
DE: 1894 Instruments and techniques: modeling
SC: Hydrology [H]
MN: 2007 Joint Assembly