HR: 11:25h
AN: H32A-05    [Abstracts]
TI: Jacob's Interpretation Method Revisited: Accounting for 3-D Spatial Heterogeneity
AU: * Sanchez-Vila, X
EM: xavier.sanchez-vila@upc.edu
AF: Technical University of Catalonia, Jordi Girona 1-3, Barcelona, 08034 Spain
AU: Riva, M
EM: monica.riva@polimi.it
AF: Politecnico di Milano, Piazza Leonardo da Vinci 32, Milano, 20133 Italy
AU: Guadagnini, A
EM: alberto.guadagnini@polimi.it
AF: Politecnico di Milano, Piazza Leonardo da Vinci 32, Milano, 20133 Italy
AU: Carrera, J
EM: jesus.carrera@upc.edu
AF: Technical University of Catalonia, Jordi Girona 1-3, Barcelona, 08034 Spain
AB: Traditional approaches to hydraulic test interpretation provide typically individual aquifer parameters, such as hydraulic conductivity (K) and storativity (S) values. The values obtained somehow incorporate some averaging values of aquifer heterogeneity, while the averaging functions are a direct consequence of the method of analysis employed. In recent years most work, casted in a stochastic framework, focused on the relationship between pumping rate and ensemble mean or variance of drawdown, thus having to pre-specify the parameters characterizing the underlying random spatial function. On the contrary, we contend that additional highly relevant information about heterogeneity can be obtained by looking to the spatial distribution of drawdown in individual realizations of the heterogeneous K field, without the need for invoking ergodic arguments. We present an analysis of the spatial distribution of time-dependent drawdown in a tridimensional aquifer produced by constant rate pumping in a fully penetrating well. The aquifer is considered of infinite extension in the x, y directions, and we assume no-flow boundaries in the aquifer top and bottom. The observation point is a fully penetrating piezometer. We consider an unknown spatial distribution of K(x,y,z), and using a perturbation expansion up to second order, we look at the late-time behavior of drawdown at any given observation vertical line. We conclude that: (1) at any given observation line the late-time behavior of drawdown would display a straight line in a drawdown versus log time plot, thus allowing the use of Jacob's method for test interpretation; (2) the slope of the straight line is the same for each observation line, thus providing a global average of K(x,y,z) through the aquifer; (3) the intercept point of the line in the same plot depends on location and is related to connectivity issues between the pumping and observation locations; (4) the intercept value is a weighted function of the local values of K at any given location times a spatially variable kernel, showing the relative importance of each individual K value.
DE: 1828 Groundwater hydraulics
DE: 1849 Numerical approximations and analysis
DE: 1869 Stochastic hydrology
SC: Hydrology [H]
MN: Fall Meeting 2005