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A partially-coupled hydro-mechanical analysis of the Bengal Aquifer System under hydrological loading

A partially-coupled hydro-mechanical analysis of the Bengal Aquifer System under hydrological loading
A partially-coupled hydro-mechanical analysis of the Bengal Aquifer System under hydrological loading
The coupled poro-mechanical behaviour of geologic-fluid systems is fundamental to numerous processes in structural geology, seismology and geotechnics but is frequently overlooked in hydrogeology. Substantial poro-mechanical influences on groundwater head have recently been highlighted in the Bengal Aquifer System, however, driven by terrestrial water loading across the Ganges-Brahmaputra-Meghna floodplains. Groundwater management in this strategically important fluvio-deltaic aquifer, the largest in south Asia, requires a coupled hydro-mechanical approach which acknowledges poro-elasticity. We present a simple partially-coupled, one-dimensional poro-elastic model of the Bengal Aquifer System, and explore the poro-mechanical responses of the aquifer to surface boundary conditions representing hydraulic head and mechanical load under three modes of terrestrial water variation. The characteristic responses, shown as amplitude and phase of hydraulic head in depth profile and of ground surface deflection, demonstrate (i) the limits to using water levels in piezometers to indicate groundwater recharge, as conventionally applied in groundwater resources management; (ii) the conditions under which piezometer water levels respond primarily to changes in the mass of terrestrial water storage, as applied in geological weighing lysimetry; (iii) the relationship of ground surface vertical deflection to changes in groundwater storage; and (iv) errors of attribution that could result from ignoring the poroelastic behaviour of the aquifer. These concepts are illustrated through application of the partially-coupled model to interpret multi-level piezometer data at two sites in southern Bangladesh. There is a need for further research into the coupled responses of the aquifer due to more complex forms of surface loading, particularly from rivers.
1607-7938
2461-247
Woodman, Nicholas
9870f75a-6d12-4815-84b8-6610e657a6ad
Burgess, William
e294bd81-7ae7-4f7f-aad8-746222f07973
Ahmed, Kazi Matin
d832f8dc-bb5e-4f40-af8d-b77d0d9c8e72
Zahid, Anwar
ffc45bf5-aaa2-44bf-9c51-0b3bb9eff552
Woodman, Nicholas
9870f75a-6d12-4815-84b8-6610e657a6ad
Burgess, William
e294bd81-7ae7-4f7f-aad8-746222f07973
Ahmed, Kazi Matin
d832f8dc-bb5e-4f40-af8d-b77d0d9c8e72
Zahid, Anwar
ffc45bf5-aaa2-44bf-9c51-0b3bb9eff552

Woodman, Nicholas, Burgess, William, Ahmed, Kazi Matin and Zahid, Anwar (2019) A partially-coupled hydro-mechanical analysis of the Bengal Aquifer System under hydrological loading. Hydrology and Earth System Sciences, 23 (5), 2461-247, [hess-2018-304]. (doi:10.5194/hess-2018-304).

Record type: Article

Abstract

The coupled poro-mechanical behaviour of geologic-fluid systems is fundamental to numerous processes in structural geology, seismology and geotechnics but is frequently overlooked in hydrogeology. Substantial poro-mechanical influences on groundwater head have recently been highlighted in the Bengal Aquifer System, however, driven by terrestrial water loading across the Ganges-Brahmaputra-Meghna floodplains. Groundwater management in this strategically important fluvio-deltaic aquifer, the largest in south Asia, requires a coupled hydro-mechanical approach which acknowledges poro-elasticity. We present a simple partially-coupled, one-dimensional poro-elastic model of the Bengal Aquifer System, and explore the poro-mechanical responses of the aquifer to surface boundary conditions representing hydraulic head and mechanical load under three modes of terrestrial water variation. The characteristic responses, shown as amplitude and phase of hydraulic head in depth profile and of ground surface deflection, demonstrate (i) the limits to using water levels in piezometers to indicate groundwater recharge, as conventionally applied in groundwater resources management; (ii) the conditions under which piezometer water levels respond primarily to changes in the mass of terrestrial water storage, as applied in geological weighing lysimetry; (iii) the relationship of ground surface vertical deflection to changes in groundwater storage; and (iv) errors of attribution that could result from ignoring the poroelastic behaviour of the aquifer. These concepts are illustrated through application of the partially-coupled model to interpret multi-level piezometer data at two sites in southern Bangladesh. There is a need for further research into the coupled responses of the aquifer due to more complex forms of surface loading, particularly from rivers.

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Accepted/In Press date: 8 April 2019
e-pub ahead of print date: 22 May 2019

Identifiers

Local EPrints ID: 430319
URI: http://eprints.soton.ac.uk/id/eprint/430319
ISSN: 1607-7938
PURE UUID: 3469638e-c02e-4b0d-b16e-bbd1a48e1210
ORCID for Nicholas Woodman: ORCID iD orcid.org/0000-0002-5571-0451

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Date deposited: 25 Apr 2019 16:30
Last modified: 29 Oct 2023 02:51

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Contributors

Author: William Burgess
Author: Kazi Matin Ahmed
Author: Anwar Zahid

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