The depth to the water table is calculated from the difference between the ground level (elevation) and the level of the groundwater surface, or, in the case of confined conditions, the lower edge of the overburden (aquitard).
The present map of May 2020 differs from that of May 2009 in that a considerably improved elevation model was available for calculating the depth to the water table. With the digital terrain model DTM1, which has a grid width of 1 m and an accuracy of +/- 0.1 m, the elevation data is now based on a high-resolution and reliable model of the terrain surface that covers the entire State of Berlin. The DTM1 model (as of July 13, 2021) was used.
The ascertainment of the groundwater surface is based on data from the groundwater measurement points of the Berlin State Groundwater Service (Landesgrundwasserdienst) and from the Berlin Waterworks (BWB) of May 2020. In addition, measurement data from the Brandenburg State Office for the Environment (LfU Brandenburg) and from water supply companies in the Berlin area were integrated into the process. More information on the statistical base and the map development method may be found in the commentary on Map 02.12 “Groundwater Levels of the Main Aquifer and Panke Valley Aquifer”.
With the help of digital information on hydrogeological sections from the Geological Atlas (SenStadt 2002) of Berlin, as well as selected boreholes from the borehole archive, areas with confined groundwater surfaces were identified in Berlin. In these areas, the lower edges of the aquitards were recorded, rather than the water levels at the measurement points. Map 02.07 “Depth to the Water Table 2009” describes this process at length, which is why it is omitted here.