[Thermal impact of subsurface urban structures on groundwater temperatures in the city of Basel].

In Basel (CH), the thermal impact of various subsurface structures on urban groundwater resources, including five underground parking lots and a freeway tunnel, were investigated by monitoring systems. Data were analyzed together with meteorological and groundwater temperature data and results from heat-transport modelling.Significantly elevated temperatures between 18.8 and 21.1 °C were recorded in the underground parking lots, even in winter. Thus, underground parking lots emit heat into the surroundings all year. In comparison, data recorded in the freeway tunnel indicate that in the winter months heat can also be absorbed from below ground.In addition, the temperatures of underground parking lots show a clear dependence on the type of use: with a higher number of daily entrances and exits, greater daily temperature increases were detected, with differences of up to 2 °C. This became particularly clear in the "lockdown" period during the COVID-19 pandemic between March and May 2020.