GEOPHYSICAL MAPPING OF BURIED VALLEY AQUIFER SYSTEMS

The access to clean water is a basic requirement for human life and economic development. The water supply in the North Sea region is mainly based on groundwater resulting in a high standard with respect to water quality and supply guaranty. Increasing water demand and increasing danger of pollution make it necessary to localize and to safeguard new groundwater reservoirs.

Buried valleys are geological structures that can contain large groundwater reservoirs. These structures are widespread over the north European sedimentary basin. Their groundwater reservoirs are already used by an increasing number of water works. For a sustainable water supply, detailed knowledge of the structure of the water reservoirs within the valleys including their vulnerability is required. This is the data base for action plans to protect the water reservoirs.

The aim of the EU project BurVal was to contribute to a sustainable water supply from buried valley aquifers by the following steps: - to test and develop geophysical and hydrogeological techniques for improved characterization of buried valley aquifer systems; - to use these methods to achieve a database for action plans for groundwater protection; to disseminate the project results to stakeholders from water supply organisations and administrations.

Therefore, geophysical and hydrogeological techniques were tested and further developed in six pilot areas. Targets for geophysical exploration of buried valleys are: 1) localisation and lateral extent (the valley is not visible at the surface), 2) shape and depth extent, 3) composition of the valley fill in terms of aquifers and impermeable layers, 4) structure of the covering layers in order to quantify the aquifer vulnerability.

Results of the investigation program showing the combined use of geophysical techniques to characterize buried valleys are presented and discussed.