OR/14/070 Summary

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Taylor, R G1, Burgess, W G1, Shamsudduha, M1, Zahid, A2, Lapworth, D J3, Ahmed, K4, Mukheriee, A5 and Nowreen, S6. 2014. Deep groundwater in the Bengal Mega-Delta: new evidence of aquifer hydraulics and the influence of intensive abstraction. British Geological Survey Internal Report, OR/14/070.

1  University College London (UCL), UK;     2  Bangladesh Water Development Board, Bangladesh;     3  British Geological Survey, UK;     4  Dhaka University, Bangladesh;     5  Indian Institute of Technology (Kharagpur), India;     6  Bangladesh University of Engineering & Technology, Dhaka, Bangladesh

This report describes the findings of a Case Study on Deep groundwater in the Bengal Mega-Delta: new evidence of aquifer hydraulics and the influence of intensive abstraction, a component of the BGS research programme ‘Groundwater resources in the Indo-Gangetic Basin: resilience to climate change and pumping’. The report focusses on the security of deep groundwater in the coastal region of the Bengal Aquifer System (BAS) of the Ganges-Brahmaputra-Meghna (GBM) delta. It addresses the principal points of uncertainty concerning deep groundwater recharge and vulnerability to ingress of arsenic as the aquifer system responds to the combined stresses of climate change and anthropogenic influences.

The two primary research activities are first described: depth-specific groundwater monitoring, and analysis of changes in rainfall intensity throughout the 21st century. Allied research is reported, on the security of alternative deep groundwater pumping strategies, shallow groundwater dynamics in relation to arsenic concentration, and groundwater-surface water relationships. A summary of field activities and field data collected is provided.

The preliminary findings are presented as depth-specific profiles of groundwater heads and chemistry from nested monitoring stations instrumented under the study, and as projected intensification of rainfall in Bangladesh over the period 2070–2099 relative to 1961–1990. These findings, together with the outcomes of allied research on deep groundwater pumping strategies and shallow groundwater dynamics, improve understanding of BAS at the depths where abstraction is rapidly accelerating, the hydraulic connectivity between the deep and shallow parts of the aquifer system, and the likely impact of climate change.

Our analysis justifies the cautious expansion of deep groundwater pumping in Bangladesh under a robust regime for regulating abstractions and monitoring groundwater levels and groundwater quality. Further questions are identified which will need to be addressed to support management of the deep groundwater resource and further development of policy.