HR: 08:30h
AN: H11I-02    [Abstracts]
TI: Outcrop-Based Lidar Imagery to Develop Millimeter-Scale Models of Heterogeneity
AU: * Weissmann, G S
EM: weissman@unm.edu
AF: University of New Mexico, Department of Earth and Planetary Sciences MSC03 2040 1 University of New Mexico, Albuquerque, NM 87131-0001, United States
AU: Frechette, J D
EM: jdfrech@unm.edu
AF: University of New Mexico, Department of Earth and Planetary Sciences MSC03 2040 1 University of New Mexico, Albuquerque, NM 87131-0001, United States
AU: William, W
EM: woodruff@unm.edu
AF: University of New Mexico, Department of Earth and Planetary Sciences MSC03 2040 1 University of New Mexico, Albuquerque, NM 87131-0001, United States
AU: Elizabeth, N
EM: enichols@unm.edu
AF: University of New Mexico, Department of Earth and Planetary Sciences MSC03 2040 1 University of New Mexico, Albuquerque, NM 87131-0001, United States
AU: Timothy, W F
EM: tfw@unm.edu
AF: University of New Mexico, Department of Earth and Planetary Sciences MSC03 2040 1 University of New Mexico, Albuquerque, NM 87131-0001, United States
AU: Katherine, K A
EM: kaklise@sandia.gov
AF: Sandia National Laboratories, Geohydrology Department PO Box 5800, Albuquerque, NM 87185-0735, United States
AB: Dispersion in ground water systems is largely believed to be due to variable velocity fields caused by aquifer heterogeneity; however, models that capture realistic heterogeneities are often elusive. In order to evaluate the influence of outcrop-scale heterogeneities (e.g., 2-5 meters), we interpret lithofacies from detailed outcrop scans using high-resolution (3-5 mm-scale) terrestrial lidar. To delineate lithofacies from the outcrop images, we apply both automated and semi-automated segmentation methods in a hierarchical approach. We first define bounding surfaces that surround lithofacies units. We then segment lithologic classes (e.g., gravel, sand, or silt) within these units. By applying reasonable hydraulic conductivity values to each lithology and populating a grid at the resolution of the lidar scan with these conductivities, we can build 2D groundwater flow and particle tracking models that capture this ‘realistic' heterogeneity as observed in outcrop. We apply this approach to several outcrops in order to evaluate flow characteristics through different facies assemblages. The resulting groundwater simulations show that cross-bedding within a unit focuses flow and transport along select pathways, typically coarse-grained units. In some cases, flow may be focused inside less than 10% of the total aquifer volume. Additionally, truncated gravel cross-beds can focus flow through adjacent, finer-grained beds. Transport through these heterogeneous realizations is markedly non-Fickian.
DE: 1800 HYDROLOGY
DE: 1829 Groundwater hydrology
DE: 1831 Groundwater quality
DE: 1832 Groundwater transport
SC: Hydrology [H]
MN: 2007 Fall Meeting