Hydrogeological overview map of Lower Saxony 1: 500 000 — Extraction conditions in groundwater rocks (WMS Service)
Description
For the assessment of the aquifers, the extraction conditions (delivery potentials) are estimated. This refers to the Brunn energy efficiency or the economic efficiency of groundwater abstractions, whereby a sufficient groundwater requirement is required.
Unfavorable extraction conditions are present in low-power or poorly permeable aquifers, good conditions with correspondingly greater thickness or better permeability. Transmissivity (product of permeability coefficient and thickness) is used as a measure in the looser rock. As part of the visualisation possibilities, only the overall transmissivity is taken into account, even if two or more separate aquifers are formed. For an area-based statement, there are not enough transmissivity determinations from hydraulic investigations, therefore an estimation is made on the basis of layer registers of the numerous digestion and well drilling. Standard permeability coefficients (kf values) were used for the main petrographic components, which were determined by the evaluation of a larger number of pump tests. For the groundwater deposits in solid rock, brunch energy levels are used for comparative estimation.
The rocks occurring in Lower Saxony are divided into four classes that characterise how good the conditions for the extraction of groundwater are.
Very good extraction conditions correspond to transmissivities of more than 100 m²/h. They prevail wherever very powerful, well groundwater-conducting layer packages are present. These conditions are given in Lower Saxony in the Lüneburg and Aurich areas, where quaternary and tertiary predominantly sandy aquifers form a powerful conductor complex that is still deepened in the area of quaternary gutter systems and filled with coarse sediment material. In these areas, very large amounts of groundwater can be produced in the long term with relatively little reduction, because the corresponding supply from the new groundwater formation is also guaranteed.
Good extraction conditions are available for transmissivities between 20 and 100 m²/h. Such conditions exist everywhere in the distribution area of quaternary glazifluviatile loose rocks in northern Germany, including the gravel fulfilment of the river valleys of the larger rivers. Even in solid rocks, there can be quite good extraction conditions (e.g. Pöhlder Basin) in narrow regionally limited, highly rugged and karst zones.
Aquifers of this category are potentially suitable for the extraction of larger amounts of groundwater.
Unfavorable extraction conditions are present in transmissivities below 20 m²/h. In loose rocks, these conditions are mainly encountered where low-power quaternary sediments lie above clay tertiary layers or in the boundary area to the solid rock. In the hard rock areas, the extraction conditions are often unfavorable. The aquifers of this group are generally not suitable as well sites for larger groundwater abstractions.
Strongly changing extraction conditions are present in areas where there is no uniform characteristic of the extraction conditions, for example in the area of diving moraines and in some cases also in solid rock.
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https://nibis.lbeg.de/net3/public/ogc.ashx?NodeId=54&Service=WMS&Request=GetCapabilities& |
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