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Time‐lapse imaging of saline‐tracer transport in fractured rock using difference‐attenuation radar tomography

Water Resources Research

By:
ORCID iD , ORCID iD , , and
https://doi.org/10.1029/2002WR001722

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Abstract

Accurate characterization of fractured‐rock aquifer heterogeneity remains one of the most challenging and important problems in groundwater hydrology. We demonstrate a promising strategy to identify preferential flow paths in fractured rock using a combination of geophysical monitoring and conventional hydrogeologic tests. Cross‐well difference‐attenuation ground‐penetrating radar was used to monitor saline‐tracer migration in an experiment at the U.S. Geological Survey Fractured Rock Hydrology Research Site in Grafton County, New Hampshire. Radar data sets were collected every 10 min in three adjoining planes for 5 hours during each of 12 tracer tests. An innovative inversion method accounts for data acquisition times and temporal changes in attenuation during data collection. The inverse algorithm minimizes a combination of two functions. The first is the sum of weighted squared data residuals. Second is a measure of solution complexity based on an a priori space‐time covariance function, subject to constraints that limit radar‐attenuation changes to regions of the tomograms traversed by high difference‐attenuation ray paths. The time series of tomograms indicate relative tracer concentrations and tracer arrival times in the image planes; from these we infer the presence and location of a preferential flow path within a previously identified zone of transmissive fractures. These results provide new insights into solute channeling and the nature of aquifer heterogeneity at the site.

Additional publication details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Time‐lapse imaging of saline‐tracer transport in fractured rock using difference‐attenuation radar tomography
Series title:
Water Resources Research
DOI:
10.1029/2002WR001722
Volume:
39
Issue:
10
Year Published:
2003
Language:
English
Publisher:
American Geophysical Union
Description:
Article 1290; 14 p.
First page:
10-1
Last page:
10-14