Remote detection of saline intrusion in a coastal aquifer using borehole measurements of self potential
File(s)
Published version
Supporting information
Author(s)
MacAllister, Donald John
Jackson, MD
Butler, Adrian P
Vinogradov, J
Type
Journal Article
Abstract
Two years of self‐potential (SP) measurements were made in a monitoring borehole in the coastal UK Chalk aquifer. The borehole SP data showed a persistent gradient with depth, and temporal variations with a tidal power spectrum consistent with ocean tides. No gradient with depth was observed at a second coastal monitoring borehole ca. 1 km further inland, and no gradient or tidal power spectrum were observed at an inland site ca. 80 km from the coast. Numerical modeling suggests that the SP gradient recorded in the coastal monitoring borehole is dominated by the exclusion‐diffusion potential, which arises from the concentration gradient across a saline front in close proximity to, but not intersecting, the base of the borehole. No such saline front is present at the two other monitoring sites. Modeling further suggests that the ocean tidal SP response in the borehole, measured prior to breakthrough of saline water, is dominated by the exclusion‐diffusion potential across the saline front, and that the SP fluctuations are due to the tidal movement of the remote front. The electrokinetic potential, caused by changes in hydraulic head across the tide, is one order of magnitude too small to explain the observed SP data. The results suggest that in coastal aquifers, the exclusion‐diffusion potential plays a dominant role in borehole SP when a saline front is nearby. The SP gradient with depth indicates the close proximity of the saline front to the borehole and changes in SP at the borehole reflect changes in the location of the saline front. Thus, SP monitoring can be used to facilitate more proactive management of abstraction and saline intrusion in coastal aquifers.
Date Issued
2018-03-10
Date Acceptance
2018-02-14
Citation
Water Resources Research, 2018, 54 (3), pp.1669-1687
ISSN
0043-1397
Publisher
American Geophysical Union
Start Page
1669
End Page
1687
Journal / Book Title
Water Resources Research
Volume
54
Issue
3
Copyright Statement
© 2018 The Authors. This is an open access article under the terms of the Creative Commons Attribution‐NonCommercial‐NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non‐commercial and no modifications or adaptations are made (https://creativecommons.org/licenses/by-nc-nd/4.0/).
Identifier
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2017WR021034
Subjects
Science & Technology
Life Sciences & Biomedicine
Physical Sciences
Environmental Sciences
Limnology
Water Resources
Environmental Sciences & Ecology
Marine & Freshwater Biology
self-potential
seawater Intrusion
coastal aquifers
exclusion-diffusion potential
electrokinetic potential
hydrogeophysics
ELECTRICAL-RESISTIVITY TOMOGRAPHY
HYDRAULICALLY ACTIVE FRACTURES
HYDROCARBON RESERVOIRS
CONTAMINANT TRANSPORT
CARBONATE AQUIFERS
SOUTHERN ENGLAND
JOINT INVERSION
CHALK AQUIFER
POROUS-MEDIA
TRACER TEST
Environmental Engineering
0406 Physical Geography and Environmental Geoscience
0905 Civil Engineering
0907 Environmental Engineering
Publication Status
Published
Date Publish Online
2018-02-16