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Groundwater resources and vulnerability in the Cretaceous Chalk of Northern Ireland

By
S. Barnes
S. Barnes
Geology Department, The Queen’s University of Belfast, Belfast, Northern Ireland BT7 1NN, UK
Present address: S.I.T.A., Narborough Lodge, Huncote Road, Narborough, Leicester LE9 5RQ, UK (e-mail: narborough_lodge@sita.fr)
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Published:
January 01, 2000

Abstract

A confined Cretaceous Chalk aquifer underlies approximately one quarter of Northern Ireland, yet little is known about its groundwater resource potential. This issue has been addressed on the catchment scale by analysing spring discharge and hydrochemical fluctuations.

The Chalk springs are recharged by allogenic leakage and surface runoff from overlying Tertiary basalts. Sources connected to river-sinks show greater variation in flow and quality reflecting a much shorter residence time than those predominantly derived from the diffuse recharge. Discharge from the confined region becomes proportionally significant during prolonged dry spells, but is typically a minor component compared with groundwater circulation volumes in the unconfined region.

Spring flood recessions are rapid (recession coefficients up to 0.125 per day) and suggest that the Chalk has a high hydraulic conductivity and a low storage capacity. These characteristics together, with the essentially impermeable matrix, are consistent with an aquifer dominated by a dispersed fracture network.

Conceptual aquifer classification suggests that the outcrop region is a highly sensitive karst aquifer. The subcrop areas can only be exploited via boreholes and are likely to be less productive, although the water quality has been shown to be more stable and less vulnerable to contamination.

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Geological Society, London, Special Publications

Groundwater in the Celtic Regions: Studies in Hard Rock and Quaternary Hydrogeology

N. S. Robins
N. S. Robins
British Geological Survey, Wallingford, UK
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B. D. R. Misstear
B. D. R. Misstear
University of Dublin, Trinity College, Ireland
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Geological Society of London
Volume
182
ISBN electronic:
9781862394308
Publication date:
January 01, 2000

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