Hydrogeological overview map of Lower Saxony 1 : 200 000 - salinisation of groundwater

Description

The map shows the possible groundwater salinization on a scale of 1:200,000. Freshwater-filled aquifers can only be found in Lower Saxony to a maximum depth of 300 m. Their occurrence is limited to the areas in which a constant water exchange by seepage rainwater takes place (zone of active water exchange). Among them, an increasing salinization of the groundwater can be observed (zone of delayed water exchange). At greater depths, an area with largely stagnant groundwater follows. The close relationship between freshwater resources and active water exchange makes groundwater dynamics a central criterion in the assessment of the usability of aquifers as well as in the delimitation of groundwater bodies. The depth of the salinized waters, i.e. the draught of the active water exchange, is essentially controlled by the hydraulic properties of the rock layers and the potential of the flowing freshwater bodies. It therefore varies greatly. Large-scale pressure gradients can occur in large pre-flood areas (e.g. Elbe, Weser, and Allernied) in which the hydrostatic pressure is abruptly reduced as a result of the transfer of large quantities of groundwater into the pre-flood areas, causing deep salinised waters to penetrate into the shallow groundwater area (inland salinisation ). The salinization areas in deep groundwater are often bound to the quaternary meltwater channels cut into the older subsoil. The depth of the salinization lies at a level where no aquifers are formed outside the gutters. Inland, about 400 km2 are also to be classified as groundwater salinisation areas caused by irrigation processes on high-lying salt domes (salt dome irrigation, subrosion, cf. salt structures of northern Germany 1: 500 000, © BGR, 2008). On the North Sea coast, as a result of the general sea level rise after the last ice age, seawater has penetrated the inland aquifers on a broad front (coastal salinisation ), displacing the fresh water contained in them. Affected by this type of groundwater salinization is a coastal strip up to 20 km wide, a total of 2500 km2, which is therefore largely precarious for groundwater use. Only on the coastal islands have freshwater lenses formed among the dune areas due to seepage rainfall, which allow drinking water to be pumped to a limited extent. In total, areas with a total area of around 6500 km2 in Lower Saxony are affected by groundwater salinisation, which makes groundwater use difficult or impossible. To delineate the areas with salinized groundwater, the results of water analyses, geoelectric probing and outcrop drilling were evaluated with geophysical borehole measurements. A water is referred to as salted if its chloride content exceeds 250 mg/l, which corresponds approximately to the human taste limit. The map distinguishes in the loose rock whether the entire groundwater body is salted or whether saltwater was only encountered in part of the groundwater. Only near-surface salinizations, also in the area of salt heaps, are shown in the solid rock.

Resources

Name Format Description Link
0 https://nibis.lbeg.de/net3/public/ogc.ashx?NodeId=61&Service=WMS&Request=GetCapabilities&

Tags

  • opendata
  • inspireidentifiziert
  • nibis-metadaten
  • sgd_hydrogeologie

Topics

  • TECH

Categories