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Role of geographical information systems and groundwater modelling in water resource management for small islands: a case study from St Martin’s and St Agnes, Isles of Scilly, UK

By
David C. Watkins
David C. Watkins
Camborne School of Mines, University of Exeter, Redruth, Cornwall TR15 3SE, UK (e-mail: D.C.Watkins@csm.ex.ac.uk
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Published:
January 01, 2000

Abstract

Common to other small islands, water resource management is a critical issue on the Isles of Scilly, UK. This study examined the current practice of water management on the islands of St Martin’s and St Agnes in the Isles of Scilly so that a local water management plan could be formulated. The study commenced with a survey of water supplies which included locating wells, rainwater tanks and septic tanks and determining their connections and utility. Wellheads were level surveyed with respect to UK Ordnance Datum, allowing reduced groundwater levels to be monitored. Groundwater is abstracted from shallow dug wells in blown sand or Head deposits and deep wells bored into fractured granite. Hydraulic tests were conducted in seven wells to determine well and aquifer characteristics, although these tests were limited by the low yields of the wells. A geographical information system was used to collate and process information. MODFLOW and MODPATH models were constructed to help interpret the hydrogeology; to determine the impact and sustainability of groundwater abstractions; and to determine the possible extent of source protection zones around wells. The present rate of abstraction is sustainable but, due to large natural variations in the water table level, groundwater resources will always be vulnerable during periods of dry weather. The main threats to existing groundwater supplies are saline intrusion, elevated nutrient levels from agriculture and bacterial contamination from septic tanks.

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Contents

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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