Palaeowaters in European coastal aquifers – the goals and main conclusions of the PALAEAUX project
W. M. Edmunds, 2001. "Palaeowaters in European coastal aquifers – the goals and main conclusions of the PALAEAUX project", Palaeowaters in Coastal Europe: Evolution of Groundwater since the Late Pleistocene, W. M. Edmunds, C. J. Milne
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The Palaeaux project has brought together up-to-date geochemical, isotopic and hydrogeological information on coastal groundwaters across Europe in a transect from the Baltic to the Canary Islands. These data have been interpreted in relation to past climatic and environmental conditions, as well as extending and challenging concepts about the evolution of groundwater near the present day coastlines. Groundwater movement beyond the present coastline as well as emplacement on shore to greater depths (up to 500 m) than allowed by the present-day flow regime has occurred, hence offshore freshwater reserves are inferred in some coastal areas. The main attributes of palaeowaters, in terms of water quality, are their high bacterial purity, total mineralization that is often less than that of modem waters and being demonstrably free of anthropogenic chemicals. However, in the Mediterranean coastal areas, lower recharge leads to higher salinity conditions in both palaeo- and modem waters.
Freshwater of high quality originating from different climatic conditions to the present day, when the sea level was much lower, is found at depth beneath the present-day coastline in several countries. Recharge is shown to have been more or less continuous during the past 100 ka, even beneath the ice, as demonstrated by groundwaters from Estonia, having δ18O values of c. −22%. However, elsewhere (UK and Belgium) an age gap can be recognized indicating that no recharge took place at the time of the last glacial maximum. Devensian recharge temperatures (soil air temperatures) were some 6°C colder across Europe than at the present day.
The development of aquifers in Europe during the past 50–100 a, by abstraction from boreholes, has generally disturbed flow systems that have evolved over varying geological timescales, especially those derived from the Late Pleistocene and Holocene. Hydrogeophysical logging has demonstrated time and quality stratified aquifers resulting in mixed waters being produced on pumping. A range of specific indicators, including 3H, 3H/3He, 85Kr, chlorofluorocarbons and pollutants, have been used to recognize the extent to which waters from the modern (industrial) era have penetrated into the aquifers, often replacing the natural palaeogroundwaters.
In the coastal regions, many problems for management are identified, including issues relating to quantity and quality of water, seasonal demand, pollution risks and ecosystem damage, requiring a new look at legislation.
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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.