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Title: Four-dimensional electrical conductivity monitoring of stage-driven river water intrusion: Accounting for water table effects using a transient mesh boundary and conditional inversion constraints

This paper describes and demonstrates two methods of providing a-priori information to a surface-based time-lapse three-dimensional electrical resistivity tomography (ERT) problem for monitoring stage-driven river bank storage along the Columbia River in the state of Washington, USA. First, a transient warping mesh boundary is implemented that conforms to the known location of the water table boundary through time, thereby enabling the inversion to place a sharp bulk-conductivity contrast at that boundary without penalty. Second, because river water specific conductance is less than groundwater specific conductance, a non-linear inequality constraint is used to allow only negative transient changes in bulk conductivity to occur within the saturated zone during periods of elevated river stage with respect to baseline conditions. Whereas time-lapse imaging results using traditional smoothness constraints are unable to delineate river bank storage, the water table and inequality constraints provide the inversion with the additional information necessary to resolve the spatial extent of river water intrusion through time. A surface based ERT array of 352 electrodes was used to autonomously produce four images per day of changes in bulk conductivity associated with river water intrusion over an area of approximately 300 m2 from April through October of 2013. Results are validatedmore » by comparing changes in bulk conductivity time series with corresponding changes in fluid specific conductance at several inland monitoring wells.« less
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Publication Date:
OSTI Identifier:
Report Number(s):
Journal ID: ISSN 0043-1397; 47870; KP1702030
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Water Resources Research; Journal Volume: 51; Journal Issue: 8
American Geophysical Union (AGU)
Research Org:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org:
Country of Publication:
United States
groundwater river water interaction; resistivity; inversion; imaging; hydrogeophysics; hydrology; Environmental Molecular Sciences Laboratory