title: Hydraulic Tomography: Continuity and Discontinuity of High-K and Low-K Zones.
abstract: Hydraulic tomography is an emerging field and modeling method that provides a continuous hydraulic conductivity (K) distribution for an investigated region. Characterization approaches that rely on interpolation between one-dimensional (1D) profiles have limited ability to accurately identify high-K channels, juxtapositions of lenses with high K contrast, and breaches in layers or channels between such profiles. However, locating these features is especially important for groundwater flow and transport modeling, and for design and operation of in situ remediation in complex hydrogeologic environments. We use transient hydraulic tomography to estimate 3D K in a volume of 15-m diameter by 20-m saturated thickness in a highly heterogeneous unconfined alluvial (clay to sand-and-gravel) aquifer with a K range of approximately seven orders of magnitude at an active industrial site in Assemini, Sardinia, Italy. A modified Levenberg-Marquardt algorithm was used for geostatistical inversion to deal with the nonlinear nature of the highly heterogeneous system. The imaging results are validated with pumping tests not used in the tomographic inversion. These tests were conducted from three of five clusters of continuous multichannel tubing (CMTs) installed for observation in the tomographic testing. Locations of high-K continuity and discontinuity, juxtaposition of very high-K and very low-K lenses, and low-K "plugs" are evident in regions of the investigated volume where they likely would not have been identified with interpolation from 1D profiles at the positions of the pumping well and five CMT clusters. Quality assessment methods identified a suspect high-K feature between the tested volume and a lateral boundary of the model.
authors.forename: David L
authors.initials: DL
authors.lastname: Hochstetler
authors.affiliation: Department of Civil and Environmental Engineering, Stanford University, 473 Via Ortega, Stanford, CA, 94305. wbarrash@stanford.edu.|Center for Geophysical Investigation of the Subsurface, Department of Geosciences, Boise State University, 1910 University Drive, Boise, ID, 83705. wbarrash@stanford.edu.
authors.forename: Warren
authors.initials: W
authors.lastname: Barrash
authors.affiliation: Center for Applied Geoscience, University of Tübingen, Tübingen, Germany.. carsten.leven-pfister@uni-tuebingen.de.
authors.forename: Carsten
authors.initials: C
authors.lastname: Leven
authors.affiliation: Department of Geoscience, University of Wisconsin-Madison, Madison, WI.. cardiff@wisc.edu.
authors.forename: Michael
authors.initials: M
authors.lastname: Cardiff
authors.affiliation: Dipartimento di Ingegneria per l'Ambiente e il Territorio e Ingegneria Chimica, Università della Calabria, via P Bucci 42B, 87036, Rende, Italy.. francescochidichimo@boisestate.edu.
authors.forename: Francesco
authors.initials: F
authors.lastname: Chidichimo
authors.affiliation: Department of Civil and Environmental Engineering, Stanford University, 473 Via Ortega, Stanford, CA, 94305. peterk@stanford.edu.
authors.forename: Peter K
authors.initials: PK
authors.lastname: Kitanidis
mesh_terms: D004784:Environmental Monitoring / Q000379:methods*; D060587:Groundwater / Q000032:analysis*; D062070:Hydrology / Q000379:methods; D007558:Italy; D008962:Models, Theoretical; D014054:Tomography / Q000295:instrumentation / Q000379:methods*; D014872:Water Movements