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.地下水面（groundwater surface）或承压地下水（tensioned groundwater）的地下水压力面，通常以地下水等势线（groundwater equalisation，isohypses）表示。本地图主题展示下萨克森州（Lower Saxony）所有松散岩区的首个大型地下水储库的地下水面分布。本次制图未考虑密度差异。在下萨克森州南部的基岩（solid rock）区域，此类制图方式并不适用，因为该区域通常不存在空间上连续的地下水水体。地下水在基岩的裂隙、断层系统或喀斯特（karst）空洞中运移。尽管基岩（如喀斯特区域）中的地下水赋存量可能相当可观，但在此比例尺下，以地下水等势线进行表达并无实际意义。此类区域在地图中以"基岩"标注。在下萨克森州沿海区域，地下水位受海水位潮汐变化与人工排水措施（围垦造地工程（creation plants）、潮沟排水渠（siele））的强烈影响。在陶土开采与围垦造地区域，地下水流向可由海洋指向内陆。在海岸线紧邻区域，地下水流向随潮汐状态发生变化。本次绘制的地下水等势线仅为高度概化的结果。地下水等势线的绘制通常基于所有监测点同一时刻的地下水位监测数据。本图示以1993年1月为基准参考期，代表1990-2000年序列的平均地下水位。本地图集的基准期监测数据取自国家水务部门（National Water Services）的地下水位资料，经下萨克森州水利、海岸与自然保护局（Lower Saxony State Agency for Water Management, Coastal and Nature Conservation）许可后方可使用。此外，部分数据由供水企业提供。由于基准期监测网格的点密度不足，本数据集在技术可行的前提下，补充了其他时段的地下水位监测数据。此类数据源自钻井数据库（drilling database）或下萨克森州采矿、能源与地质局（LBEG）的档案文档。但在地下水位波动剧烈的区域，未进行此类数据补充。在腹碛（abdominal moraines）区，由于此类区域的地质结构极不均一，地下水位埋深差异极大。在此类区域，地下水等势线仅能反映宏观的地下水流向。在监测点密度极低的区域，现场实际水位可能与本地图的图示存在偏差。为使地下水等势线的线划表达更为直观，其包围的区域被施以色彩填充。色彩填充面以相对于正常高基准面（Normalnull，NN）2.5米的间隔标示地下水面或地下水压力区的位置。地下水等势图（groundwater equilibrium plan）可用于阐明松散岩区的地下水流向与地下水力梯度。若需开展详细的定量分析，则需采用基准期监测点密度更高的地图。