The present maps of groundwater temperature distribution are based on the evaluation of measurement data from the years 2015 to 2020, which was recorded at more than 200 measurement points in the State of Berlin. It should be noted that for measurement depths of more than 60 m below terrain surface, the number of available measurement points decreases considerably. In some parts of the city, there are relatively large areas where temperature measurements cannot be obtained from greater depths.
In addition to single measurements, temperatures have been measured at groundwater measurement points specifically designed for that purpose at regular intervals since February 2018. These measurement points consist of a full pipe without a filter, allowing it to be filled with water to just below terrain surface. This enables the observation of the seasonal temperature development even in the subsoil not saturated with water.
In areas without current measurement data from 2020, temperature measurements recorded between 2015 and 2019 were drawn upon. In these cases, the temperature data was adjusted to the 2020 measurements by area. As a rule, temperature profiles are recorded from the water table to the excavation depth with a measuring point spacing of 1 m.
Measurement error arising from calibration and measurement inaccuracy of the device or measurement inaccuracy of the measured object (e.g., due to heat convection at the measurement points) is estimated to be ±0.1°C.