You don’t have to dig deep to find groundwater in Berlin. In the Warsaw-Berlin glacial spillway, which extends from the Spandauer Forst in the north-west to the Müggelsee in the south-east, you’d have to dig between half a metre and a max of 7 metres. Experts describe the difference between the earth’s surface and the groundwater level underground as “depth to the water table”. This parameter is not a constant but varies depending on the groundwater levels. On the one hand, the latter depend on natural influences such as rain, evaporation or the underground path water takes to percolate. On the other hand, consumers impact upon groundwater levels, as does industrial and construction activity.
For any kind of construction measure, from single-family homes to high rises, for any kind of traffic structure (canals, roads, tunnels) and for supply and disposal lines (telecommunications cables, water and sewage pipes, gas and electricity supply), it is crucial to keep an eye on the depth to the water table. In this context, the highest groundwater level, which equals the shortest depth to the water table of an area, is of particular importance for construction planning and implementation. Disregarding these groundwater levels may cause flooded basements and, worst case scenario, base failure leading to the complete destruction of a building.
The depth to the water table, however, also plays a key role for groundwater-dependent land ecosystems, such as bogs, alluvial forests and wet meadows. Groundwater levels have decreased since the 19th century, especially around the Berlin Waterworks (BWB). Today, wetlands, such as the Hundekehlefenn in Grunewald, can only be preserved through water management measures. Berlin has been making efforts for years to prevent further lowering of the groundwater table. Large construction projects, for example, have to replace the groundwater that is extracted on their behalf. This and other initiatives have been proven successful.
There are two current editions: the 2009 edition illustrates depths to the water table based on medium groundwater levels. The 2020 edition represents depths to the water table in relation to low groundwater levels. Older editions indicate historical depths to the water table relating to the terrain elevation data available at the time.