Hydrogeological map of Lower Saxony 1: 50 000 — Average monthly groundwater regeneration 1971-2000 in January, method mGROWA22 (WMS service)

The map shows the mean monthly groundwater formation for the month of January in the 30-year period 1971-2000. Groundwater is a raw material that can regenerate and renew itself.The main supplier for the groundwater supply is precipitation water leaking in Lower Saxony. It ensures that the groundwater deposits of the storage rocks are replenished in the underground. The groundwater formation is particularly high in winter, as at this time a large part of the rainfall in the soil is leaking. In the warmer seasons, on the other hand, much of the precipitation already evaporates on the surface or is absorbed by plants. The new groundwater formation is widely distributed in different areas. It depends on the distribution of precipitation and evaporation, the characteristics of the soil, the land use (growth, degree of sealing), the relief of the land surface, the artificial drainage by drainage, the groundwater fluid level and the properties of the near-surface rocks. Since these parameters differ significantly in the smallest space in Lower Saxony, groundwater formation is also subject to large lateral fluctuations. In order to determine the new groundwater formation, there are different methods. The available maps show the area-differentiated designation of the mean groundwater formation, which was calculated using the mGROWA method (short for “monthly large-scale water balance”). The model mGROWA was developed for the large-scale simulation of the water balance at Forschungszentrum Jülich in cooperation with the LBEG (Herrmann et al. 2013) and updated methodically for Lower Saxony since 2016. In addition, a series of new input data has been used to provide an up-to-date data base for water management planning and water approval procedures. As climatic input data, daily and monthly measured and subsequently spatially interpolated climate observation data from the German Weather Service were used. These are the potential evaporation calculated on the basis of FAO grass reference evaporation (DWD, unpublished) and precipitation based on the REGNIE product (Rauthe et al, 2013) corrected by Richter (Judge, 1995). For better regionalisation, the climatic input parameters precipitation and potential evaporation with bilinear interpolation were scaled down to a 100 x 100 m grid for mGROWA22.本地图展示了1971-2000年30年周期内1月份的平均地下水补给量(groundwater formation)。地下水是一种可自我再生更新的自然资源。下萨克森州(Lower Saxony)的地下水补给主要来源于入渗降水。 它保障了地下储水岩层中的地下水储量得到补充。冬季的地下水补给量尤其高，因为此时土壤中的大部分降雨会渗入地下。而在较温暖的季节，多数降水会在地表蒸发或被植物吸收。新增的地下水补给广泛分布于不同区域。 其数值取决于降水与蒸发的分布、土壤特性、土地利用方式（植被覆盖度、地表密封程度）、地表地形、人工排水措施、地下水位以及近地表岩层的性质。由于下萨克森州内这些参数在极小空间范围内就存在显著差异，地下水补给量也会出现较大的横向波动。 为测算新增地下水补给量，存在多种方法。本次提供的地图展示了经分区差异化标注的平均地下水补给量，该数据通过mGROWA方法（为“月度大尺度水平衡(monthly large-scale water balance)”的缩写）计算得出。 mGROWA模型由于利希研究中心(Forschungszentrum Jülich)与LBEG合作开发（Herrmann等，2013），并自2016年起针对下萨克森州进行了系统性更新。此外，研究团队还采用了一系列新的输入数据，为水资源管理规划与取水许可审批流程提供了最新的数据库支撑。 本次研究采用的气候输入数据，来源于德国气象局(German Weather Service, DWD)的实测逐日、逐月气候观测数据及后续空间插值结果。这些数据包括基于FAO参考草面蒸发量(FAO grass reference evaporation)计算的潜在蒸发量（DWD，未公开数据），以及经Richter（Judge，1995）校正的、基于REGNIE数据集(REGNIE product)的降水数据（Rauthe等，2013）。 为实现更精准的区域化处理，研究团队通过双线性插值(bilinear interpolation)将降水与潜在蒸发这两项气候输入参数的分辨率降至100×100米网格，以适配mGROWA22模型。