Drinking water and large portions of water for other uses in Berlin are withdrawn from groundwater (“true” groundwater and bank-filtered water). This resource continually varies in quantity and quality. A well-functioning groundwater measuring network is necessary to secure and maintain water resources. Only constant control of both groundwater withdrawals and natural and artificial recharges can prevent excessive removals and overexploitation.
All construction activities intervene in the subsurface. The Berlin subsurface is characterized by strongly varying local ground and groundwater conditions. Local groundwater conditions must be known, especially for deeper construction works (traffic tunnels and deep foundations), in order to prevent irregular subsidence, lift dangers, and moisture damage. A knowledge of the deepest and highest groundwater levels is critical for planning and construction.
Development of Lowering of Groundwater
The first lowering of groundwater tables in the Berlin area (and the destruction of wetlands) occurred with the dewatering of swampy areas, such as the Hopfenbruch in Wilmersdorf in the 18th century. Additional areas were dewatered in the 19th and 20th century during the great expansion of canals. Groundwater levels sank due to increased demands for drinking and industrial water, by water retention at construction sites, and the restricting of groundwater recharge caused by (impervious) sealing of surface areas.
The industrial development of Berlin began in the mid-1880’s and caused groundwater levels to sink to a low point in 1939. The economic collapse after the Second World War allowed groundwater levels to rise almost to pre-industrial levels.
Groundwater levels sank continually in large areas during the next era, from the beginning of the 50’s till the beginning of the 80’s, because of increasing withdrawals. Lowered groundwater was particularly noticeable in drinking water production areas. This was caused by a general increase of water consumption by households and construction, the post-war rebuilding of Berlin, subways and other large engineering projects. West Berlin’s enlargement of water production plants in its borough waterworks was completed at the beginning of the 70’s. An enlargement of the East Berlin Friedrichshagen waterworks was begun in the mid-70’s to supply the new, large residential settlements in Hellersdorf, Marzahn and Hohenschönhausen.
Berlin’s water needs are primarily satisfied by withdrawing water from aquifers located in ice age Pleistocene strata. Aquifers are porous and water-permeable subterranean layers of rock that hold and allow water to flow. The upper aquifer is extremely important. The aquifer base is formed by semi-permeable or impermeable silt, clay and boulder marl. Medium sands with fine and coarse pockets make up most of the groundwater conducting layer. Groundwater flows through layers of differing thickness depending on hydrogeological conditions.
Making of Groundwater Contour Maps
Although groundwater levels in Berlin have been measured for the last 100 years, groundwater contour maps for the entire city area have not been produced. The division of Berlin in 1948 caused geologic and hydrogeologic explorations to be done separately. All geologic and hydrogeologic data in the GDR (German Democratic Republic) was considered confidential material. That prevented a common effort.
Groundwater contour maps at a scale of 1:50,000 have been produced for West Berlin at the beginning and at the middle of the hydrographic year (November and May) since November, 1953. They were prepared by the Department of Construction and Housing and are now prepared by the Berlin Department of Urban Development and Environmental Protection. They are published yearly in the “Gewässerkundlichen Jahresbericht des Landes Berlin (Hydrological Annual Report of Berlin). Groundwater contour maps for East Berlin appeared at irregular intervals as “Hydrogeologische Karten” (Hydrogeological Maps).
The fusion of the Oberflußmeisterei (Head River Master) and its groundwater measuring points with the West Berlin water authorities in 1991 allowed the preparation of a groundwater contour map for all Berlin for the first time.