The visualisation of the protection potential of aquifer covering strata is a contribution of the State Geological Surveys (SGD) to describe the groundwater bodies as part of the reporting commitment for implementing the European Water Framework Directive. The indicated protection potential refers to the upper contiguous aquifer based on the specifications of the LAWA working guideline and suggests a categorisation of good, medium or poor protection potential. Depending on the availability of adequate digital information to assess the protection potential, two approaches have been established by the federal states. Approach 1: Using conventional empirical methods, the states of Berlin, Brandenburg, Hesse, Mecklenburg-Vorpommern, Lower Saxony, North Rhine-Westphalia, Rhineland-Palatinate, Saarland, Saxony and Schleswig-Holstein have classified existing spatial information (from HÜK 200 or other state-specific basic information) and / or point information (profiles of boreholes) regarding their potential protective effect towards the intrusion of contaminants and have interpreted these according to LAWA guidelines. Approach 2: In the states of Baden-Württemberg, Bavaria, Hamburg, Saxony-Anhalt and Thuringia a methodology – developed by the SGD´s – for the determination of the protection potential of aquifer covering strata (HÖLTING et al., Geol. Jb. C 63, Hannover 1995) was applied. It concludes in more differentiated statements, however, it requires comprehensive information on percolation rate / groundwater recharge, available field capacity of the soil, rock type and thickness of the aquifer covering strata, the structural properties of the hard rocks and artesian conditions. The classification is based on a scoring system and was translated according to LAWA standards. Areas of stagnant surface water and areas with insufficient information density have not been rated.
Horizontal cross-section maps display the geological situation at a given depth. In concurrence of maps at different depths areal bedding conditions can be determined, e.g. to generally assess and interpret the spread of different stratigraphic units. Clearly visible are extent and shape of the salt structures within their regional context at the different depths, with extent and boundary of the salt structures having been the main focus of the project. Four horizontal cross-section maps covering the whole onshore area of Northern Germany have been developed at a scale of 1:500.000. The maps cover the depths of -500, -1000, -1500, -2000 m below NN. The four depths were selected by the project partners and are based on typical depth requirements of existing salt caverns in Northern Germany, mainly related to hydrocarbon storage. The shapes of the structures show rudimentary information of their geometry and their change with depths. In addition they form the starting point for rock mechanical calculations necessary for the planning and construction of salt caverns for storage as well as for assessing storage potentials. The maps can be used as a pre-selection tool for subsurface uses. It can also be used to assess coverage and extension of salt structures. As, at the time of preparation of the maps, energy storage and cavern operation in offshore areas could not be assumed as a priority, such areas were not treated within the project. All horizontal cross-section maps were adjusted with the respective state geological survey organisations.
The map of the field capacity of soils in Germany gives an overview of the amount of water which can be stored in a soil (depth 1 m). The water storage capacity is a key function of soils. The field capacity was derived from the landuse stratified soil map of Germany at scale 1:1,000,000. The method is published in the Bodenkundliche Kartieranleitung KA4 (1994) and in the documentation of Ad-hoc-AG Boden (representing the soil experts of the geological services of the German federal states). The land use information is derived from the CORINE Land Cover data set (2006).
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