The groundwater temperature in the Berlin metropolitan area is permanently anthropogenically influenced.
The temperature measurements of the near-surface groundwater of the State of Berlin carried out since the 1980s show that the average temperature has increased to a level more than 4°C above that in the thinly populated surrounding areas outside the city. They also indicate that this temperature rise is increasingly apparent even at depths greater than 20 m.
Fig. 1: Schematic Diagram of the Factors that Affect Groundwater Temperature
The causes of the temperature rise are various, and are directly connected to the continuing structural developments and the existing uses at the earth's surface. There, the distinction is made between direct and indirect influences on the groundwater temperature (see Fig. 1):
These differences cause changes in the heat balance by comparison with the areas surrounding the city.
The city is gradually heating itself up, storing ever more heat overall, and gradually passing it on again to the surrounding areas, i.e., it can generally be considered a huge heat storage unit. Over the long term, this process leads to an increase in the annual mean air temperatures (cf. Map of long-term mean air temperatures, 1961-'90; Map 04.02).
The long-term warming also leads to a heating of the groundwater. The physical qualities and the chemical and biological nature of the groundwater are temperature-dependent. As a result of such warming, a deterioration of groundwater quality and an impairment of the groundwater fauna may result.
One hundred percent of Berlin’s drinking water comes from groundwater, which is extracted almost exclusively from the territory of the State of Berlin. The groundwater also supplies a large share of the water for industrial use. Therefore, the protection of the groundwater from serious change, such as a significant increase in groundwater temperature, is of great importance – especially in the interests of sustainable water management.
Since 1978, temperature profiles have increasingly been recorded at deep groundwater measurement points distributed throughout the area of the city, in order to ascertain and observe changes.
The purpose of the present map is:
In addition, it can, in combination with other topical maps, such as the Geological Outline Map (Map 01.17), the Groundwater Levels and Catchment Areas Map (Map 02.12), or the Geothermal Potential Map (Map 02.18), be used as an aid for decision-making and for preliminary planning for energy management of the groundwater. The underground temperature is an important quantity for the installation of ground heat exchangers.