Hydrogeological overview map of Lower Saxony 1: 200 000 — Location of the groundwater surface

The position of the groundwater surface, or the groundwater pressure surface with tensioned groundwater, is usually represented by aquifers (isohypses). The map theme shows the groundwater surface for all loose rock regions of Lower Saxony. In the solid rock areas of southern Lower Saxony, this type of representation is not possible, 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. These areas are marked as solid rocks on the map, the presumed groundwater flow direction is indicated by arrows. For the construction of the groundwater equivalents, groundwater level measurements are generally used at all measuring points at the same time. Reference date measurements are available for larger territorial units, but not nationwide for the whole of Lower Saxony. Therefore, groundwater level measurements had to be used for the present groundwater equalisation plan at different times, which were converted to mean water level ratios. The evaluation included all measuring stations that are monitored in the context of the Land Water Management Service. In addition to these measuring stations in the state service, there are many other measuring stations, which are monitored as part of waterworks, evidence-keeping procedures and special programs and were also used for this map. In order to make the line representation of the groundwater equals more vivid, the intermediate surfaces are colored. The colour surfaces indicate the position of the groundwater surface or the groundwater pressure area in m to NN. The groundwater equilibrium plan is suitable for clarifying the flow directions and the potential gradients of groundwater in the loose rock areas.