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Projections of historical and 21st century fluvial sediment delivery to the Ganges-Brahmaputra-Meghna, Mahanadi, and Volta deltas

Projections of historical and 21st century fluvial sediment delivery to the Ganges-Brahmaputra-Meghna, Mahanadi, and Volta deltas
Projections of historical and 21st century fluvial sediment delivery to the Ganges-Brahmaputra-Meghna, Mahanadi, and Volta deltas

Regular sediment inputs are required for deltas to maintain their surface elevation relative to sea level, which is important for avoiding salinization, erosion, and flooding. However, fluvial sediment inputs to deltas are being threatened by changes in upstream catchments due to climate and land use change and, particularly, reservoir construction. In this research, the global hydrogeomorphic model WBMsed is used to project and contrast ‘pristine’ (no anthropogenic impacts) and ‘recent’ historical fluvial sediment delivery to the Ganges-Brahmaputra-Meghna, Mahanadi, and Volta deltas. Additionally, 12 potential future scenarios of environmental change comprising combinations of four climate and three socioeconomic pathways, combined with a single construction timeline for future reservoirs, were simulated and analysed. The simulations of the Ganges-Brahmaputra-Meghna delta showed a large decrease in sediment flux over time, regardless of future scenario, from 669 Mt/a in a ‘pristine’ world, through 566 Mt/a in the ‘recent’ past, to 79–92 Mt/a by the end of the 21st century across the scenarios (total average decline of 88%). In contrast, for the Mahanadi delta the simulated sediment delivery increased between the ‘pristine’ and ‘recent’ past from 23 Mt/a to 40 Mt/a (+77%), and then decreased to 7–25 Mt/a by the end of the 21st century. The Volta delta shows a large decrease in sediment delivery historically, from 8 to 0.3 Mt/a (96%) between the ‘pristine’ and ‘recent’ past, however over the 21st century the sediment flux changes little and is predicted to vary between 0.2 and 0.4 Mt/a dependent on scenario. For the Volta delta, catchment management short of removing or re-engineering the Volta dam would have little effect, however without careful management of the upstream catchments these deltas may be unable to maintain their current elevation relative to sea level, suggesting increasing salinization, erosion, flood hazards, and adaptation demands.

Climate change, Hydrogeomorphic modelling, Reservoir construction, Socioeconomic change
0048-9697
105-116
Dunn, Frances E.
474bab5b-3065-474c-aa8a-433275d62601
Nicholls, Robert J.
4ce1e355-cc5d-4702-8124-820932c57076
Darby, Stephen E.
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Cohen, Sagy
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Zarfl, Christiane
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Fekete, Balazs
7a6419d5-4552-4c4f-842b-5188926a769f
Dunn, Frances E.
474bab5b-3065-474c-aa8a-433275d62601
Nicholls, Robert J.
4ce1e355-cc5d-4702-8124-820932c57076
Darby, Stephen E.
4c3e1c76-d404-4ff3-86f8-84e42fbb7970
Cohen, Sagy
99521dde-cd3d-46ff-8cba-3c1fca9e73d4
Zarfl, Christiane
f3e76e7d-c154-4fb8-bd38-7165519a2cb9
Fekete, Balazs
7a6419d5-4552-4c4f-842b-5188926a769f

Dunn, Frances E., Nicholls, Robert J., Darby, Stephen E., Cohen, Sagy, Zarfl, Christiane and Fekete, Balazs (2018) Projections of historical and 21st century fluvial sediment delivery to the Ganges-Brahmaputra-Meghna, Mahanadi, and Volta deltas. Science of the Total Environment, 642, 105-116. (doi:10.1016/j.scitotenv.2018.06.006).

Record type: Article

Abstract

Regular sediment inputs are required for deltas to maintain their surface elevation relative to sea level, which is important for avoiding salinization, erosion, and flooding. However, fluvial sediment inputs to deltas are being threatened by changes in upstream catchments due to climate and land use change and, particularly, reservoir construction. In this research, the global hydrogeomorphic model WBMsed is used to project and contrast ‘pristine’ (no anthropogenic impacts) and ‘recent’ historical fluvial sediment delivery to the Ganges-Brahmaputra-Meghna, Mahanadi, and Volta deltas. Additionally, 12 potential future scenarios of environmental change comprising combinations of four climate and three socioeconomic pathways, combined with a single construction timeline for future reservoirs, were simulated and analysed. The simulations of the Ganges-Brahmaputra-Meghna delta showed a large decrease in sediment flux over time, regardless of future scenario, from 669 Mt/a in a ‘pristine’ world, through 566 Mt/a in the ‘recent’ past, to 79–92 Mt/a by the end of the 21st century across the scenarios (total average decline of 88%). In contrast, for the Mahanadi delta the simulated sediment delivery increased between the ‘pristine’ and ‘recent’ past from 23 Mt/a to 40 Mt/a (+77%), and then decreased to 7–25 Mt/a by the end of the 21st century. The Volta delta shows a large decrease in sediment delivery historically, from 8 to 0.3 Mt/a (96%) between the ‘pristine’ and ‘recent’ past, however over the 21st century the sediment flux changes little and is predicted to vary between 0.2 and 0.4 Mt/a dependent on scenario. For the Volta delta, catchment management short of removing or re-engineering the Volta dam would have little effect, however without careful management of the upstream catchments these deltas may be unable to maintain their current elevation relative to sea level, suggesting increasing salinization, erosion, flood hazards, and adaptation demands.

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Accepted/In Press date: 1 June 2018
e-pub ahead of print date: 14 June 2018
Published date: 15 November 2018
Keywords: Climate change, Hydrogeomorphic modelling, Reservoir construction, Socioeconomic change

Identifiers

Local EPrints ID: 421725
URI: http://eprints.soton.ac.uk/id/eprint/421725
ISSN: 0048-9697
PURE UUID: 52443914-6201-4997-a44a-bc5a1a698a80
ORCID for Robert J. Nicholls: ORCID iD orcid.org/0000-0002-9715-1109
ORCID for Stephen E. Darby: ORCID iD orcid.org/0000-0001-8778-4394

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Date deposited: 25 Jun 2018 16:30
Last modified: 18 Feb 2021 17:02

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Contributors

Author: Frances E. Dunn
Author: Sagy Cohen
Author: Christiane Zarfl
Author: Balazs Fekete

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