Modelling scenarios for the emplacement of palaeowaters in aquifer systems
W. G. Harrar, A. T. Williams, J. A. Barker, M. Van Camp, 2001. "Modelling scenarios for the emplacement of palaeowaters in aquifer systems", Palaeowaters in Coastal Europe: Evolution of Groundwater since the Late Pleistocene, W. M. Edmunds, C. J. Milne
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The response of coastal aquifer systems to global sea-level rise, the presence of permafrost and glaciation has been analysed using analytical and numerical models. The hydraulic connectivity between confined coastal aquifers and the sea largely controls their response to global sea-level rise. Open aquifer systems have direct hydraulic contact with the sea where they sub crop along the continental slope and base-level history for the aquifer is defined by sea-level history. In these systems, hydraulic heads equilibrate quickly to sea-level change at rates controlled by the aquifer hydraulic diffusivity. Interface movement lags behind the equilibration of the hydraulic heads and is controlled largely by the rate at which freshwater can be flushed from the aquifer through overlying semi-confining units. Interface movement occurs over time periods of tens of thousands of years. In contrast, closed aquifer systems lack direct hydraulic connectivity with the sea, which is controlled by the thickness and permeability of overlying semi-confining layers. During the Late Pleistocene–Early Holocene the base-level history for closed aquifer systems underlying the North Sea Basin was defined by the location of rivers and lakes in areas that are now offshore. These aquifers became coastal aquifers during the Holocene when rivers and lakes were inundated by rising sea levels. Salinization of closed aquifer systems may occur due to the downward diffusion of salts through overlying semiconfining layers in the presence of upward freshwater seepage. Aquifers overridden by glaciers respond in a manner that is largely controlled by aquifer transmissivity and geometry. The presence of permafrost inhibits recharge resulting in lower hydraulic heads and a reduction in aquifer fluxes.
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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.