Hydrogeological map of Lower Saxony 1: 50 000 — Average monthly groundwater formation 1991-2020 in June, method mGROWA22

The map shows the mean monthly groundwater formation for the month of June in the 30-year period 1991-2020. 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 These are the potential evaporation calculated on the basis of FAO grass reference evaporation (DWD, unpublished) and precipitation based on the REGNIE product (Rauthe et al, 2013) corrected by Richter (Judge, 1995).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1991-2020年这30年间6月的月均地下水生成量（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）境内的入渗降水是地下水补给的主要来源。该过程可使储水岩层中的地下储水量得到补充。冬季地下水生成量尤为充沛，此时土壤中的大部分降雨会渗入地下；而在较为温暖的季节，大部分降水会在地表蒸发或被植物吸收。 新增地下水生成量在不同区域广泛分布，其空间格局取决于降水与蒸发的分布特征、土壤属性、土地利用方式（植被覆盖状况、地表封闭程度）、地表地形、人工排水措施、地下水位以及近地表岩层的特性。由于下萨克森州内上述参数在极小空间尺度内便存在显著差异，地下水生成量也会出现较大的横向空间波动。 为测算新增地下水生成量，可采用多种方法。本次公开的地图展示了经区域分异标注的月均地下水生成量，其计算采用了mGROWA方法（全称"月度大尺度水平衡模型"，monthly large-scale water balance）。mGROWA模型由于利希研究中心（Forschungszentrum Jülich）与LBEG合作开发，用于大尺度水平衡模拟（Herrmann等，2013年），并自2016年起针对下萨克森州进行了系统性更新。此外，本次研究采用了一系列全新的输入数据，可为水资源管理规划与取水审批流程提供最新的数据库支撑。 本次研究采用的气候输入数据，源自德国气象局（DWD）的逐日、逐月实测气候观测数据，经空间插值处理后得到。其中，潜在蒸散发量基于联合国粮食及农业组织（FAO）参考草田蒸散发量计算得到（德国气象局，未公开数据）；降水数据则源自REGNIE数据集（Rauthe等，2013年），并经Richter修正（Judge，1995年）。为实现更精准的区域化处理，针对mGROWA22模型，研究人员采用双线性插值法将降水与潜在蒸散发这两项气候输入参数的空间分辨率降至100米×100米网格。