Climate Change Also Warms Vienna's Groundwater

The project focus of Geosphere was on the temperature analysis of Viennese groundwater and its long-term development, it was said on Wednesday in a press release, for which measurement data from the past 20 years from 87 measuring stations were evaluated. "In addition, we measured temperature profiles in the groundwater at 800 measuring points in one April and one October, from a few meters to around 40 to 50 meters deep," says Cornelia Steiner, Geosphere expert for geothermal energy. The Viennese groundwater was coolest in April and warmest in October, after winter and summer temperatures only have a delayed effect.

"Urban Heat Island Effect" in Viennese Groundwater

The groundwater is several degrees warmer in many regions of Vienna than in the surrounding area. According to Steiner, there are two reasons for the "Urban Heat Island Effect": firstly, the higher air temperature, because streets and buildings heat up more and "secondly, the extensive underground infrastructure heats the groundwater, for example subway and road tunnels, parking garages, sewer systems, district heating pipes and pure cooling applications of geothermal energy." The average of all 800 measuring points was 13 degrees Celsius in April and 15 degrees Celsius in October. The temperature difference of the groundwater between sealed and unsealed areas is on average about four to six degrees per year.

The warming changes the biological and chemical quality of the groundwater on the one hand and affects applications such as geothermal energy on the other hand, which is currently only allowed in Vienna in the range of five to 18 degrees Celsius. Further warming could therefore lead to restrictions here. Meanwhile, no facilities are approved in Vienna that serve only for cooling, in order to avoid excessive warming of the groundwater.

Catalogue of Measures with Recommendations for Viennese Groundwater

Based on the scientific results, a catalogue of measures is now being developed that provides authorities and politicians with recommendations for an integrative management for the sustainable and efficient thermal use of groundwater. The project, funded by the Vienna Science, Research and Technology Fund (WWTF), was carried out in collaboration with the University of Vienna (project management), the University of Natural Resources and Life Sciences Vienna, Geosphere Austria and the City of Vienna (M45, Viennese Waters). The Viennese data can be accessed in the Geothermal Atlas. Among other things, it allows an initial estimate of the energy potential of geothermal probes and groundwater heat for each location and will be gradually extended to other federal states, Geosphere announced.

(APA/Red)

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