HR: 14:40h
AN: H13H-05    [Abstracts]
TI: Energy-Based Spatial Weighting Functions and Equivalent Hydraulic Conductivity in Heterogeneous Porous Media.
AU: * Molz, F J
EM: fredi@clemson.edu
AF: Environmental Engineering and Geology, Clemson University, 342 Computer Court, Anderson, SC 29625 United States
AU: Guan, J
EM: jguan@clemson.edu
AF: Environmental Engineering and Geology, Clemson University, 342 Computer Court, Anderson, SC 29625 United States
AB: To improve understanding of property measurements in heterogeneous media, an energy-based weighting function concept was developed [Molz et al., WRR, 39(4), DAN-1, 2003]. In (assumed) homogeneous media, the instrument spatial weighting function (ISWF) depends only on the energy dissipation distribution set up by the measurement procedure, and it reduces to simply inverse sample volume (uniform weighting) for the 1-D parallel flow case (ideal permeameter). For 1-D transient flow in homogeneous media, such as with slug tests, the ISWF varies with position and time, with 95% of the total weighting contained within 115 well radii, even late in the test [Molz et al., Ground Water, in press, 2004]. The present talk deals with the heterogeneous case, which is what one deals with in natural systems. Thus, in actual measurements, the identification of the ISWF is connected to the problem of determining an "equivalent" hydraulic conductivity (Ke), and it would be ideal if the criterion for "equivalence" based on energy-dissipation- rate-weighting would produce the same Ke as that based on the common permeameter test. It can be shown that for 1-D linear and radial flow in heterogeneous porous media, the energy-dissipation based Ke and the usual Ke calculated using assumed homogeneity and Darcy's law are identical. We will explore whether this same equivalence holds in general for 2-D and 3-D heterogeneity. The results to date imply that as one makes K measurements in heterogeneous media at different locations or on different cores of heterogeneous materials, the ISWF will be heterogeneity-dependent, implying that the averaging process resulting in the "equivalent" K value also varies with position. If the testing procedure is transient, then the averaging process varies also with time. This suggests a fundamental ambiguity in the interpretation of hydraulic conductivity measurements in heterogeneous media that may impact how we approach modeling and prediction in a practical sense. Several equivalent K calculations and spatial weighting functions are presented, conclusions drawn and further research suggested.
DE: 5114 Permeability and porosity
DE: 1829 Groundwater hydrology
DE: 1832 Groundwater transport
DE: 1869 Stochastic processes
DE: 1894 Instruments and techniques
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting