HR: 11:40h
AN: H21F-06    [PDF]
TI: Hydraulic Tomography and the Impact of A Priori Information: An Alluvial Aquifer Field Example
AU: * Zhan, X
EM: xyz@ku.edu
AF: Kansas Geological Survey University of Kansas, 1930 Constant Ave., Campus W, Lawrence, KS 66047 United States
AU: Bohling, G C
EM: geoff@kgs.ku.edu
AF: Kansas Geological Survey University of Kansas, 1930 Constant Ave., Campus W, Lawrence, KS 66047 United States
AU: Knoll, M D
EM: mknoll@cgiss.boisestate.edu
AF: Center for Geophysical Investigation of the Shallow Subsurface, Boise State University 1910 University Dr., Boise, ID 83725 United States
AU: Butler, J J
EM: jbutler@kgs.ku.edu
AF: Kansas Geological Survey University of Kansas, 1930 Constant Ave., Campus W, Lawrence, KS 66047 United States
AB: Hydraulic tomography is a recently developed aquifer characterization technique that involves the performance of a large number of short-term pumping tests, each of which stresses a different vertical interval in a well. Simultaneous analysis of drawdown measurements obtained from the entire set of tests provides the potential to estimate between-well hydraulic conductivity (K) variations at a higher level of detail than is possible with more conventional well tests. Hydraulic tomography is still plagued by the ubiquitous problem of non-uniqueness, so reasonable estimates of the K distribution are difficult to obtain without incorporating independent a priori information on aquifer structure. In this study, we investigate the utility of direct-push surveys and crosshole radar tomography as sources of a priori information on the spatial structure of the K field. We compare the results of analyzing a suite of tomographic pumping tests performed in an extensively studied alluvial aquifer using regularly layered zonations, zonations derived from direct-push electrical and hydraulic conductivity profiles, and zonations derived from the results of zero-offset and tomographic crosshole radar profiles. In all cases, residuals between predicted and observed head measurements, chi square values for head, and K estimates obtained at control points from slug tests or borehole flowmeter surveys are used as the basis for comparison. Although direct-push methods are an efficient means of acquiring information about aquifer structure, they cannot provide information about conditions between profile locations. Radar-based approaches can often provide valuable information about K variations between wells due to the dependence of radar propagation velocity and attenuation on sediment porosity and clay content. The value of these different types of a priori information for analyses of hydraulic tomography depends on the primary controls on K variations and the degree of lateral heterogeneity.
DE: 0994 Instruments and techniques
DE: 1894 Instruments and techniques
DE: 5114 Permeability and porosity
SC: Hydrology [H]
MN: 2003 Fall Meeting