Evolution of groundwater systems at the European coastline
W. M. Edmunds, K. Hinsby, C. Marlin, M. T. Condesso De Melo, M. Manzano, R. Vaikmae, Y. Travi, 2001. "Evolution of groundwater systems at the European coastline", Palaeowaters in Coastal Europe: Evolution of Groundwater since the Late Pleistocene, W. M. Edmunds, C. J. Milne
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An overview is given of the status and origin of fresh and saline groundwaters in the sedimentary aquifers at or near the present European coastline. Results are presented as six regional maps summarizing, as far as possible, the conditions likely to have existed at the end of the Pleistocene, after the impact of glaciation, when groundwaters might be expected to have reached their maximum offshore evolution prior to the encroachment of sea water during the Holocene marine transgression. In the eastern Baltic, the groundwater evolution was different to other European regions in that freshwater heads were higher than the present day, promoting recharge during much of the Late Pleistocene. Near the North Sea coasts, there is generally evidence of freshwater movement to depths of 100–150 m but the absence of deeper freshwater (palaeowater) storage may relate to the low hydraulic gradients in the North Sea Basin. In the southeastern part of the North Sea brackish palaeowater is found between Tertiary marine sediments c. 300 m below the island of Rømø, 10 km off the Danish west coast. Freshwater of Pleistocene and Holocene ages is found in aquifers at the English Channel coast in several areas, to depths in excess of −300 m; offshore flow in the Late Pleistocene took place towards the central palaeovalley and some of this groundwater may be preserved off the present coastline. In the two Atlantic coastal areas of France and Portugal–Spain a contrast exists due to the proximity of the continental margin and different hydraulic gradients. In Portugal, freshwaters are found at the coastline, and probably offshore, that contain evidence of recharge during the lowered sea levels. In most of the southwestern Atlantic coast of Spain, fresh recent groundwater discharges along and beyond the coastline, while in the old estuary of the Guadalquivir River, saline Holocene water still encroaches the sediments. On the Mediterranean coast of France and Spain some salinity encroachment took place during sea-level rise. In most of the Spanish aquifers fresh recent groundwater has substituted for palaeowater, except for the low-lying areas (Ebro Delta, Inca-Sa Pobla Plain) where brackish Holocene water is still present.
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Palaeowaters in Coastal Europe contains 17 contributions from an international array of authors. They discuss the history of groundwater evolution during the late Pleistocene in the coastal areas of Europe from the Baltic region to the Iberian peninsula and the Canary Islands. Geochemical and geophysical techniques for evaluating palaeowaters are reviewed. The focus of the book is on changes in the hydrogeological regime during the Quaternary and their impacts on groundwater movement and chemistry in European coastal aquifers.
The work summarized in the papers was carried out by a partnership of European scientists under the auspices of the PALAEAUX project, an EC initiative. Researchers from the fields of hydrogeology, geochemistry, isotope hydrology and Quaternary studies attempted to reconstruct the most probable movement of groundwater in the study area over the past 100 000 years and its response to climatic events of global significance during the last glacial cycle. The results of this work, summarized in this volume, allow a better understanding of the water resources found at and near the coastlines of northern and western Europe. During times of lowered sea level, it appears that groundwaters were replenished to depths greater than occur at the present day. These pristine freshwater reserves are an irreplaceable asset. Their location at coastlines where populations and water demands are high and often seasonal means that they need careful management to avoid over-exploitation or contamination. The inevitable conflicts that this resource management creates are discussed.
Palaeowaters in Coastal Europe: evolution of groundwater since the late Pleistocene will be of interest to Quarternary scientists, hydrogeologists, marine scientists engaged in coastal research and those involved in environmental science and the management of groundwater assests.