HR: 0800h
AN: H51A-0338    [Abstracts]
TI: Generalized Radial Transport for Tracer Tests in Fractured Rock
AU: * Holt, R M
EM: rmholt@olemiss.edu
AF: The University of Mississippi, Department of Geology and Geological Engineering 118 Carrier Hall, University, MS 38677 United States
AU: Roberts, R M
EM: rmrober@sandia.gov
AF: Sandia National Laboratories, 4100 National Parks Highway, Carlsbad, NM 88220 United States
AU: Bowman, D O
EM: dobowman@aol.com
AF: The University of Mississippi, Department of Geology and Geological Engineering 118 Carrier Hall, University, MS 38677 United States
AB: The double-porosity generalized radial transport model is an extension of the generalized radial flow approach developed for hydraulic test interpretation. In both approaches, a flow dimension characterizes the change in flow area versus radial distance from the borehole. The generalized radial transport model collapses to a 1D, radial, or spherical advection dispersion equation (ADE) for flow dimensions of 1, 2, and 3, respectively. Non-integer, especially sub-radial, flow dimensions are commonly reported from pumping tests in fractured rock systems and can be linked with aquifer geometry and heterogeneity. We consider the impact of sub-radial flow dimensions on convergent flow tracer tests in fractured rock. In comparison to radial transport, sub-radial transport leads to higher velocities, much earlier arrival times, and higher peak concentrations in breakthrough curves. Faster advective transport leads to less diffusion into fracture-bounded matrix blocks and steeper slopes of late time concentrations. Larger blocks, corresponding to slower diffusion rates, are undersampled. Transport and diffusion parameters estimated from sub-radial tracer tests using a radial ADE will lead to underestimates of dispersivity and diffusive capacity and overestimates of diffusion rates.
DE: 1828 Groundwater hydraulics
DE: 1832 Groundwater transport
DE: 1894 Instruments and techniques: modeling
SC: Hydrology [H]
MN: Fall Meeting 2005