HR: 0800h
AN: H21E-1050    [Abstracts]
TI: Comparison of hydraulic parameters measured at multiple scales in a synthetic heterogeneous aquifer
AU: * Craig, A
EM: ajcraig@engineering.uiowa.edu
AF: Department of Civil and Environmental Engineering, University of Iowa, 4105 Seamans Center for the Engineering Arts and Sciences, Iowa City, IA 52242 United States
AU: * Craig, A
EM: ajcraig@engineering.uiowa.edu
AF: IIHR-Hydroscience & Engineering, 300 South Riverside Drive, Iowa City, IA 52242 United States
AU: Illman, W A
EM: walter-illman@uiowa.edu
AF: Department of Geoscience, University of Iowa, 121 Trowbridge Hall, Iowa City, IA 52242 United States
AU: Illman, W A
EM: walter-illman@uiowa.edu
AF: Department of Civil and Environmental Engineering, University of Iowa, 4105 Seamans Center for the Engineering Arts and Sciences, Iowa City, IA 52242 United States
AU: Illman, W A
EM: walter-illman@uiowa.edu
AF: IIHR-Hydroscience & Engineering, 300 South Riverside Drive, Iowa City, IA 52242 United States
AB: Estimates of hydraulic parameters such as hydraulic conductivity (K) and specific storage (Ss) are needed to investigate a variety of problems including the evaluation of water supply, contaminant source zone delineation, and modeling of contaminant transport in heterogeneous porous and fractured media. A large number of field studies show that there is evidence that hydraulic parameter estimates vary with location and scale. Such studies are very important and have yielded considerable insight but the underlying cause(s) of the scale effects in hydraulic parameters is still unclear because of a large number of unknown factors that can affect field results. Here, we conduct a laboratory study under highly controlled conditions to examine the scale dependence of hydraulic parameters. We obtain measurements of hydraulic parameters at 5 different scales in a synthetic laboratory aquifer with a known heterogeneity distribution. Estimates of hydraulic parameters were obtained by: 1) constant head experiments on core samples extracted from 48 ports within the flow cell; 2) slug tests at each of the 48 ports; 3) single-hole tests at each of the 48 ports; 4) pumping tests conducted in a tomographic manner with pumping and observation taking place at each of the 48 ports; and, 5) a flow experiment through the entire synthetic aquifer to obtain an estimate of effective K. We analyzed the experimental results using a finite element code VSAFT2 (Yeh et al. 1993) by matching the simulation results to transient data. Results show that the geometric mean values of K are in general comparable for the core, single-hole tests, large-scale pumping tests, and the flow experiments through the entire synthetic aquifer, but the results from the slug tests are considerably lower. We find that the estimates of hydraulic parameters obtained from the pumping tests are unique but the values from the slug tests are not. For the slug test, we are only able to obtain a unique estimate of aquifer diffusivity which is the ratio between K and Ss. These results collectively suggest that pumping tests conducted in a heterogeneous formation with interpretation assuming that the medium is homogenous yields accurate values of equivalent K and Ss that approach the effective values when the pumping test is conducted long enough.
DE: 5114 Permeability and porosity
DE: 3230 Numerical solutions
DE: 1829 Groundwater hydrology
DE: 1869 Stochastic processes
DE: 1894 Instruments and techniques
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting