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AGU: Water Resources Research

 

Keywords

  • facies
  • inverse modeling
  • parameterization
  • pilot points
  • tracer test
  • zonation

Index Terms

  • 1816 - Estimation and forecasting
  • 1832 - Groundwater transport
  • 1846 - Model calibration
  • 1873 - Uncertainty assessment

Paper in Press

WATER RESOURCES RESEARCH, doi:10.1029/2011WR011203

On parameterization of the inverse problem for estimating aquifer properties using tracer data

Key Points
  • Decisions on parameterization of heterogeneity are crucial for inverse modeling
  • We aim quantify and highlight the effects of such decisions on inversion results
  • Study involves inverse modeling of synthetic and field data from DOE Rifle site

Authors:

Michael B. Kowalsky

Stefan A Finsterle

Kenneth Hurst Williams

Christopher J. Murray

Michael Commer

Darrell Newcomer

Andreas Englert

Carl I Steefel

Susan S. Hubbard

In developing a reliable approach for inferring hydrological properties through inverse modeling of tracer data, decisions made on how to parameterize heterogeneity (i.e., how to represent a heterogeneous distribution using a limited number of parameters that are amenable to estimation) are of paramount importance, as errors in the model structure are partly compensated for by estimating biased property values during the inversion. These biased estimates-while potentially providing an improved fit to the calibration data-may lead to wrong interpretations and conclusions and reduce the ability of the model to make reliable predictions. We consider the estimation of spatial variations in permeability and several other parameters through inverse modeling of tracer data, specifically synthetic and actual field data associated with the 2007 Winchester experiment from the DOE Rifle site. This site represents a challenging setting that reflects the real-world complexities and limitations of dynamic, shallow, alluvial aquifers. Our aim is to highlight and quantify the impact on inversion results of various decisions related to parameterization, such as the positioning of pilot points in a geostatistical parameterization, the handling of upgradient regions, the inclusion of zonal information derived from geophysical data or core logs, extension from 2D to 3D, assumptions regarding the gradient direction, porosity, and the semivariogram function, and deteriorating experimental conditions. This work adds to the relatively limited number of studies that offer guidance on the use of pilot points in complex real-world experiments involving tracer data (as opposed to hydraulic head data).

Received 26 July 2011; accepted 18 April 2012.

Citation: Kowalsky, M. B., S. A. Finsterle, K. H. Williams, C. J. Murray, M. Commer, D. Newcomer, A. Englert, C. I. Steefel, and S. S. Hubbard (2012), On parameterization of the inverse problem for estimating aquifer properties using tracer data, Water Resour. Res., doi:10.1029/2011WR011203, in press.