Hydrogeological map of Lower Saxony 1: 50 000 — Average monthly groundwater regeneration 1991-2020 in March, method mGROWA22 (WMS service)

The map shows the mean monthly groundwater formation for the month of March 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 These are the potential evaporation calculated on the basis of FAO grass reference evaporation (DWD, unpublished) and precipitation based on the REGNIE product (Rauthe et al, 2013) corrected by Richter (Judge, 1995).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30年周期内3月份的平均地下水补给量。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为入渗降水，该过程可使储水岩层中的地下水储量在地下得到补充。 冬季为地下水补给的高峰期，此时土壤中大部分降雨会渗入地下。而在暖季，多数降水会直接在地表蒸发或被植物吸收利用。 地下水补给量的空间分布广泛，其影响因素包括降水与蒸发的分布特征、土壤性质、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特性。由于下萨克森州内上述参数在极小空间尺度内即存在显著差异，地下水补给量也随之呈现出较大的横向波动。 为估算地下水补给量，学界已开发出多种方法。本次公开的地图展示了经分区差异化标注的平均地下水补给量，该数据通过mGROWA方法（"月尺度大尺度水平衡"的英文缩写）计算得到。 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完成了系统性更新。此外，研究团队还采用了一系列新的输入数据集，以期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。 本研究采用的气候输入数据，源自德国气象局（German Weather Service）的逐日、逐月实测观测数据及后续空间插值结果，其中包括基于FAO草地参考蒸散发计算得到的潜在蒸散发（DWD，未公开数据），以及基于REGNIE数据集（Rauthe等，2013年）的降水数据经Richter（Judge，1995年）校正后的版本。 为提升区域化精度，研究团队通过双线性插值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尺度至100×100米网格，以适配mGROWA22模型。