Groundwater temperature anomalies in central Europe

Abstract

As groundwater is competitively used for drinking, irrigation, industrial and geothermal applications, the focus on elevated groundwater temperature (GWT) affecting the sustainable use of this resource increases. Hence, in this study GWT anomalies and their heat sources are identified. The anthropogenic heat intensity (AHI), defined as the difference between GWT at the well location and the median of surrounding rural background GWTs, is evaluated in over 10 000 wells in ten European countries. Wells within the upper three percentiles of the AHI are investigated for each of the three major land cover classes (natural, agricultural and artificial). Extreme GWTs ranging between 25°C and 47°C are attributed to natural hot springs. In contrast, AHIs from 3 to 10K for both natural and agricultural surfaces are due to anthropogenic sources such as landfills, wastewater treatment plants or mining. Two-thirds of all anomalies beneath artificial surfaces have an AHI>6 K and are related to underground car parks, heated basements and district heating systems. In some wells, the GWT exceeds current threshold values for open geothermal systems. Consequently, a holistic management of groundwater, addressing a multitude of different heat sources, is required to balance the conflict between groundwater quality for drinking and groundwater as an energy source or storage media for geothermal systems. Abbreviations AHI (K) anthropogenic heat intensity AHI max (K) upper 3% percentile of the anthropogenic heat intensity AMD acid mine drainage CLC CORINE land cover DH district heating GST (°C) ground surface temperature GWT (°C) groundwater temperature GWT r (°C) rural background groundwater temperature LUC land utilisation class r seasonal radius SUHI subsurface urban heat island URG Upper Rhine Graben

Climate Change Yields Groundwater Warming in Bavaria, Germany

“…Especially when the shallow subsurface is dominated by horizontal flow, changes in atmospheric temperatures and land use represent thermal signals that are conduced to the aquifer and become visible in well-logs. These changes are pronounced in cities, where accelerated heat flux from urban warming, sealed ground, and buried infrastructures yields large scale subsurface urban heat islands (Ferguson and Woodbury, 2004;Menberg et al, 2013;Zhu et al, 2015;Benz et al, 2016;Epting et al, 2017;Bayer et al, 2019;Hemmerle et al, 2019), and urban, industrial and waste sites are revealed to cause the most prominent local heat anomalies in Central European aquifers (Tissen et al, 2019). In less-disturbed rural areas, groundwater temperatures are reported to slowly increase as well, which is obviously the response of the shallow ground to recent climate change (Maxwell and Kollet, 2008;Bloomfield et al, 2013;Kurylyk et al, 2014;Menberg et al, 2014;Colombani et al, 2016).…”

Groundwater fauna in an urban area: natural or affected?

“…In urban areas anthropogenic impacts, such as a dense building development, underground car parks, open geothermal systems and injections of thermal wastewater from industry result in local thermal alteration of groundwater up to several degrees (e.g. Taylor and Stefan, 2009;Zhu et al, 2011;Menberg et al, 2013b;Tissen et al, 2019). According to Brielmann et al (2011) annual temperature fluctuations in aquifers, caused by shallow geothermal energy systems, range between 4 °C in winter and 20 °C in summer.…”

Unravelling the process of petroleum hydrocarbon biodegradation in different filter materials of constructed wetlands by stable isotope fractionation and labelling studies

“…Due to the hydrophobic nature of hydrocarbons, the dissolution in water is low (Mackay et al 2006 ) and microorganisms will face them as drops in the water and / or adsorbed to soil and sediments. Groundwater temperatures in central Europe [10–12 °C (Tissen et al 2019 )] will also result in hydrocarbons larger than C 15 being present in the solid stage, which will further reduce bioavailability. To overcome the bioavailability issues, some degrading microorganisms are known to produce biosurfactants.…”