Hydrogeological map of Lower Saxony 1: 50 000 — Average monthly groundwater regeneration 1961-1990 in January, method mGROWA22 (WMS service)

The map shows the mean monthly groundwater formation for the month of January in the 30-year period 1961-1990. 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 These are the potential evaporation calculated on the basis of FAO grass reference evaporation (DWD, unpublished) and precipitation based on the REGNIE product (Rauthe et al, 2013) corrected by Richter (Judge, 1995).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1961年至1990年这30年周期内1月份的平均地下水生成量。 地下水是一种可自我再生更新的自然资源。下萨克森州的地下水补给主要来源于入渗降水，这一过程确保了储水岩层中的地下蓄水层得到地下补给。冬季的地下水生成量尤为可观，因为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，多数降水会直接在地表蒸发，或被植物吸收利用。 新增地下水生成量在不同区域广泛分布，其影响因素包括降水与蒸发的空间分布、土壤特性、土地利用方式（植被覆盖状况、地表封闭程度）、地表地形、人工排水设施、地下水位以及近地表岩层的属性。由于下萨克森州内这些参数在极小空间范围内便存在显著差异，地下水生成量也随之出现较大的横向空间波动。 为测算新增地下水生成量，目前存在多种方法。本次公开的地图展示了经分区差异化标注的平均地下水生成量，该数据通过mGROWA方法（“月尺度大型水量平衡”（monthly large-scale water balance）的缩写）计算得出。mGROWA模型由德国于利希研究中心（Forschungszentrum Jülich）与下萨克森州环境与农业局（LBEG）合作开发，用于大尺度水量平衡模拟（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，研究团队还采用了一系列全新的输入数据，为水资源管理规划与取水审批流程提供了最新的数据库支撑。 本研究采用的气候输入数据，来源于德国气象局（DWD, Deutscher Wetterdienst）实测并经空间插值得到的逐日与逐月气候观测资料，其中包括基于联合国粮食及农业组织（FAO, Food and Agriculture Organization of the United Nations）参考蒸散量计算得到的潜在蒸散量（DWD，未公开数据），以及基于REGNIE数据集（Rauthe等，2013年）生成、经Richter（Judge，1995年）校正的降水数据。为实现更精准的区域化模拟，研究团队采用双线性插值法将降水与潜在蒸散这两项气候输入参数的分辨率缩至100米×100米网格，以适配mGROWA22模型。