Marine electrical resistivity imaging of submarine groundwater discharge: sensitivity analysis and application in Waquoit Bay, Massachusetts, USA

Electrical resistivity imaging has been used in coastal settings to characterize fresh submarine groundwater discharge and the position of the freshwater/salt-water interface because of the relation of bulk electrical conductivity to pore-fluid conductivity, which in turn is a function of salinity....

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Bibliographic Details
Published in:Hydrogeology journal 2010-02, Vol.18 (1), p.173-185
Main Authors: Henderson, Rory D., Day-Lewis, Frederick D., Abarca, Elena, Harvey, Charles F., Karam, Hanan N., Liu, Lanbo, Lane, John W.
Format: Article
Language:English
Subjects:
Aquatic Pollution
Aquifers
Brackish
Chemical analysis
Coastal aquifers
Earth and Environmental Science
Earth Sciences
Electrical resistivity
Freshwater
Geology
Geophysics/Geodesy
Groundwater discharge
Hydrogeology
Hydrology
Hydrology/Water Resources
Saline water
Saline-freshwater interfaces
Salinity
Seawater
Sensitivity analysis
Tides
Waste Water Technology
Water analysis
Water Management
Water Pollution Control
Water Quality/Water Pollution
Water resources
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Summary:Electrical resistivity imaging has been used in coastal settings to characterize fresh submarine groundwater discharge and the position of the freshwater/salt-water interface because of the relation of bulk electrical conductivity to pore-fluid conductivity, which in turn is a function of salinity. Interpretation of tomograms for hydrologic processes is complicated by inversion artifacts, uncertainty associated with survey geometry limitations, measurement errors, and choice of regularization method. Variation of seawater over tidal cycles poses unique challenges for inversion. The capabilities and limitations of resistivity imaging are presented for characterizing the distribution of freshwater and saltwater beneath a beach. The experimental results provide new insight into fresh submarine groundwater discharge at Waquoit Bay National Estuarine Research Reserve, East Falmouth, Massachusetts (USA). Tomograms from the experimental data indicate that fresh submarine groundwater discharge may shut down at high tide, whereas temperature data indicate that the discharge continues throughout the tidal cycle. Sensitivity analysis and synthetic modeling provide insight into resolving power in the presence of a time-varying saline water layer. In general, vertical electrodes and cross-hole measurements improve the inversion results regardless of the tidal level, whereas the resolution of surface arrays is more sensitive to time-varying saline water layer.
ISSN:1431-2174
1435-0157
DOI:10.1007/s10040-009-0498-z