Self-potential as a predictor of seawater intrusion in coastal groundwater boreholes

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Title: Self-potential as a predictor of seawater intrusion in coastal groundwater boreholes
Authors: Malcolm, G
Jackson, M
MacAllister, DJ
Vinogradov, J
Butler, AP
Item Type: Journal Article
Abstract: Monitoring of self‐potentials (SP) in the Chalk of England has shown that a consistent electrical potential gradient exists within a coastal groundwater borehole previously affected by seawater intrusion (SI) and that this gradient is absent in boreholes further inland. Furthermore, a small but characteristic reduction in this gradient was observed several days prior to SI occurring. We present results from a combined hydrodynamic and electrodynamic model, which matches the observed phenomena for the first time and sheds light on the source mechanisms for the spatial and temporal distribution of SP. The model predictions are highly sensitive to the relative contribution of electrochemical exclusion and diffusion potentials, the ‘exclusion efficiency’, in different rock strata. Geoelectric heterogeneity, largely due to marls and hardgrounds with a relatively high exclusion efficiency, was the key factor in controlling the magnitude of the modelled SP gradient ahead of the saline front and its evolution prior to breakthrough. The model results suggest that, where sufficient geoelectric heterogeneity exists, borehole SP may be used as an early warning mechanism for SI.
Issue Date: Sep-2018
Date of Acceptance: 30-Jun-2018
URI: http://hdl.handle.net/10044/1/62718
DOI: https://doi.org/10.1029/2018WR022972
ISSN: 0043-1397
Publisher: American Geophysical Union
Start Page: 6055
End Page: 6071
Journal / Book Title: Water Resources Research
Volume: 54
Issue: 9
Copyright Statement: ©2018. The Authors. This is an open access article under theterms of the Creative Commons Attribution License, which permits use,distribution and reproduction in anymedium, provided the original work is properly cited (https://creativecommons.org/licenses/by/4.0/).
Keywords: Science & Technology
Life Sciences & Biomedicine
Physical Sciences
Environmental Sciences
Limnology
Water Resources
Environmental Sciences & Ecology
Marine & Freshwater Biology
self-potentials
seawater intrusion
coastal aquifers
modeling
CHALK AQUIFER
ELECTRICAL-CONDUCTIVITY
SALTWATER INTRUSION
SALINE INTRUSION
POROUS-MEDIA
RECHARGE
HYDROGEOLOGY
MANAGEMENT
HAMPSHIRE
TRANSPORT
0905 Civil Engineering
0907 Environmental Engineering
1402 Applied Economics
Environmental Engineering
Publication Status: Published
Online Publication Date: 2018-07-07
Appears in Collections:Faculty of Engineering
Civil and Environmental Engineering
Earth Science and Engineering



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