POSSIBILITIES AND LIMITATIONS IN APPLYING GEOELECTRICAL METHODS TO HYDROGEOLOGICAL PROBLEMS IN THE COASTAL AREAS OF NORTH WEST GERMANY*

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Abstract
On the basis of results of extensive geoelectrical investigations in East Frisia as well as of theoretically calculated data, it is shown to what extent geoelectrics can furnish a contribution to success during the preliminary work for the establishment of water works, or for the enlargement of existing water works, in coastal areas. One of the most important tasks in this sphere is the search for permeable beds suitable for intake, the delimitation of their thickness and extent (catchment areas), and then the location of favourable places for wells. This task is rather difficult because of thickness variations in and change of facies of the old‐pleistocene basin clay (Lauenburg clay) and the presence of Tertiary clay and fine clayey sands which, acting as impervious layers, often divide a permeable bed into several storage horizons. Further difficulties arise from the occurrence of brine bearing deposits near the coast, and water from the depths with a high salt content as a result of leaching processes around salt domes.The problems arising in this connection are illustrated with the aid of examples from the Rheiderland. The following questions seem to be the most important:a) the physical interpretation of the measurements with special regard to the principle of equivalence;b) the correlation of the physical data with the subsurface geology.