HR: 0800h
AN: H51A-0343    [Abstracts]
TI: Equivalent Transmissivity of Heterogeneous Leaky Aquifers for Steady-State Radial Flow
AU: Copty, N K
EM: ncopty@boun.edu.tr
AF: Bogazici University, Institute of Environmental Sciences Bogazici University, Istanbul, 34342 Turkey
AU: Sarioglu, M S
EM: savas.sarioglu@boun.edu.tr
AF: Bogazici University, Institute of Environmental Sciences Bogazici University, Istanbul, 34342 Turkey
AU: * Findikakis, A N
EM: anfindik@bechtel.com
AF: Bechtel National, Inc., 50 Beale Street, San Francisco, CA 94105-1895 United States
AB: In natural geologic systems, confining layers overlying and/or underlying an aquifer are seldom completely impermeable; instead, most of them leak to some extent. This study examines the problem of steady-state radial flow towards a well in heterogeneous leaky aquifers. The aquifer system considered consists of two aquifers separated by an aquitard, with a pumping well fully penetrating one of the aquifers. The log-transmissivity of the pumped aquifer is modeled as a multi-variate random spatial function with stationary mean and exponential semi-variogram, while the aquitard capacitance is assumed to be spatially uniform. Based on these conditions, an approximate expression for the upscaled or block transmissivity- defined as the transmissivity of an equivalent homogeneous leaky aquifer system with the same pumping- is proposed. The weighing expression is also used to derive the first and second moments of the upscaled transmissivity. The relation of the weighing function to the statistical parameters of the transmissivity field is discussed. A Monte Carlo approach is used to numerically validate the proposed upscaling expression. The drawdown in the leaky aquifer is simulated for different values of the aquitard capacitance and the statistical parameters describing the log-transmissivity distribution. The simulated drawdown data are then used to estimate the equivalent transmissivity of the homogeneous leaky aquifer system. Results of the Monte Carlo simulations show that the upscaled transmissivity estimated from the point transmissivity values and the equivalent transmissivity estimated from the simulated drawdown are in good agreement for wide ranges of aquifer parameters. The equivalent transmissivity of leaky heterogeneous aquifers are also compared to the equivalent transmissivity values estimated for non-leaky heterogeneous aquifers. The implications of these results on the interpretation of drawdown data in heterogeneous aquifer systems are discussed.
DE: 1828 Groundwater hydraulics
DE: 1829 Groundwater hydrology
DE: 1869 Stochastic hydrology
DE: 1894 Instruments and techniques: modeling
SC: Hydrology [H]
MN: Fall Meeting 2005