Climate change not only brings temperature and weather extremes: it also has consequences for groundwater. It is getting warmer in Vienna: from 2001 to 2010 the temperature rose by an average of 0.9 degrees, from 2011 to 2020 it was 1.4 degrees.
The main reasons are the significantly increased air temperature due to climate change and the progress of sealing. This is evident from a study by Geosphere Austria as part of the ‘Heat below the city’ project, which also determined the chemical and biological status of the groundwater.
Measurement data from the past 20 years evaluated
The focus of the Geosphere project was on groundwater temperature analysis and long-term development, the report said on Wednesday. For this purpose, measurement data from the past 20 years from 87 measuring stations have been evaluated. “In April and October we also measured temperature profiles in the groundwater at 800 measuring points, from a few meters to a depth of about 40 to 50 meters,” explains Cornelia Steiner, Geosphere expert for geothermal energy.
Temperature differences per season
The water was coolest in April and warmest in October, after winter and summer temperatures have only a delayed effect.
The groundwater in many regions of Vienna is a few degrees warmer than in the surrounding area. This is called the ‘urban heat island effect’.
The average of all 800 measuring points was 13 degrees Celsius measured in April and 15 degrees Celsius in October.
The annual average temperature difference in groundwater between sealed and uncapped areas is approximately four to six degrees.
Warming has consequences for water quality and geothermal energy
On the one hand, warming changes the biological and chemical quality of groundwater and on the other hand it affects applications such as geothermal energy, which in Vienna is currently only allowed in the range of five to eighteen degrees Celsius. Further warming could therefore lead to restrictions here. In Vienna, no cooling-only systems are currently approved to prevent excessive warming of groundwater.
Catalog of measures
Based on the scientific results, a catalog of measures is now being developed that will provide governments and politicians with recommendations for integrated management for sustainable and efficient thermal use of groundwater. The project, funded by the Vienna Science, Research and Technology Fund (WWTF), was carried out in a collaboration between the University of Vienna (project management), the University of Natural Resources and Life Sciences Vienna, Geosphere Austria and the City of Vienna. (M45, Vienna Waters).
The data on Vienna is available in the Geothermal Energy Atlas. Among other things, it allows an initial assessment of the energy potential of geothermal probes and groundwater heat for each location and will be gradually expanded to other states, Geosphere announced.
Source: Krone
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