Hydrogeological map of Lower Saxony 1: 50 000 — Groundwater surface location (WMS service)

The position of the groundwater surface, or the groundwater pressure surface with tensioned groundwater, is usually represented by groundwater equalisation (isohypses). The map theme shows the groundwater surface of the first large-scale groundwater stock plant for all loose rock areas in Lower Saxony. Density differences were not taken into account. In the solid rock areas of southern Lower Saxony, this type of representation is not practicable, since a spatially contiguous groundwater body usually does not exist there. The groundwater moves in the solid rock in cleft and fault systems or karsth hollow spaces. Although the groundwater deposits in the solid rock, e.g. in karst areas, can be quite remarkable, they are not meaningful with groundwater equals on this scale. These areas are marked as fixed rocks on the map. In Lower Saxony’s coastal area, groundwater levels are strongly influenced by the tide-related changes in the seawater level and by measures of artificial drainage (creation plants, siele). In the area of pottery and sub-creation plants, the groundwater flow direction can run away from the coast towards inland. In the immediate vicinity of the coastline, the groundwater flow direction changes depending on the state of the tide. The groundwater level equals are shown here only strongly generalised. For the construction of the groundwater equivalents, groundwater level measurements are generally used at all measuring points at the same time. This illustration is based on the January 1993 reference date and represents a mean groundwater level of the 1990-2000 series. The reference date measurements of the map series are based on groundwater level data from the National Water Services, which were used with the permission of the Lower Saxony State Agency for Water Management, Coastal and Nature Conservation. In addition, some data from water supply companies were provided. Since the grid from reference date measurements does not have sufficient document density, the database was supplemented, as far as it seemed technically reasonable, with groundwater level measurements from other periods. This data comes from the drilling database or from archive documents of the LBEG. In areas with high fluctuations in the groundwater level, this supplement was not made. In the area of abdominal moraines, groundwater distances are highly variability due to the very heterogeneous geological structure of these areas. Here, the groundwater equals can only represent the large-scale flow direction. In areas with very low document dot density, the actual water levels on site may differ from the map representation. In order to make the line representation of the groundwater equals more vivid, the surfaces enclosed by them are colored. The colour surfaces indicate the position of the groundwater surface or the groundwater pressure area at intervals of 2.5 m in meters to NN. The groundwater equilibrium plan is suitable for clarifying the flow directions and the potential gradients of groundwater in the loose rock areas. Detailed statements may require maps with a higher document density at cut-off date measurements.