HR: 11:40h
AN: H32A-06    [Abstracts]
TI: Analysis of Pumping Tests in Heterogeneous Aquifers Using CTRW Theory
AU: Knudby, C
EM: christenknudby@yahoo.com
AF: University of California, Davis Department of Land, Air, and Water Resources, 229 Veihmeyer Hall, Davis, CA 95616 United States
AU: * Cortis, A
EM: acortis@ucdavis.edu
AF: University of California, Davis Department of Land, Air, and Water Resources, 229 Veihmeyer Hall, Davis, CA 95616 United States
AB: We deal with the problem of transient flow in heterogeneous aquifers. The effect of heterogeneities on macroscopic flow and drawdown is investigated in the framework of Continuous Time Random Walk (CTRW) theory. The CTRW is an upscaled probabilistic approach based on a distribution of event times charateristic to the spectrum of heterogeneities. CTRW theory has been proved to be a very general and effective means to quantify non-Fickian solute transport. In this framework, we derive a new time dependent partial differential equation (PDE) for the diffusion of the piezometric head, h. In contrast to the classical PDE for h (derived under the assumption of homogeneity), the CTRW based PDE introduces a convolution in time with a memory function. In order to compare the two theories, we present a series of numerical simulations of 2D transient flow in formations with multi-gaussian distributions of transmissivity. We show that the classical diffusion equation fails to capture the distinct early- and late-time tailing in the fluid flux breakthrough curves. The flux breakthrough curves are better described by CTRW theory. The deviation between the two approaches is explained by CTRW theory through parameters that depend on the structure of the heterogeneity. Our analysis suggests that a significant amount of extra information on formation heterogeneity can be extracted from pumping test results if they are analyzed using CTRW theory.
DE: 1828 Groundwater hydraulics
DE: 1832 Groundwater transport
DE: 1835 Hydrogeophysics
DE: 1847 Modeling
DE: 1849 Numerical approximations and analysis
SC: Hydrology [H]
MN: Fall Meeting 2005