The thermal impact of subsurface building structures on urban groundwater resources – A paradigmatic example

Epting, Jannis and Scheidler, Stefan and Affolter, Annette and Borer, Paul and Müller, Matthias H. and Egli, Lukas and García-Gil, Alejandro and Huggenberger, Peter. (2017) The thermal impact of subsurface building structures on urban groundwater resources – A paradigmatic example. Science of the Total Environment, 596. pp. 87-96.

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Official URL: http://edoc.unibas.ch/54925/

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Shallow subsurface thermal regimes in urban areas are increasingly impacted by anthropogenic activities, which include infrastructure development like underground traffic lines as well as industrial and residential subsurface buildings. In combination with the progressive use of shallow geothermal energy systems, this results in the so-called subsurface urban heat island effect.
This article emphasizes the importance of considering the thermal impact of subsurface structures, which commonly is underestimated due to missing information and of reliable subsurface temperature data. Based on synthetic heat-transport models different settings of the urban environment were investigated, including: (1) hydraulic gradients and conductivities, which result in different groundwater flow velocities; (2) aquifer properties like groundwater thickness to aquitard and depth to water table; and (3) constructional features, such as building depths and thermal properties of building structures.
Our results demonstrate that with rising groundwater flow velocities, the heat-load from building structures increase, whereas down-gradient groundwater temperatures decrease. Thermal impacts on subsurface resources therefore have to be related to the permeability of aquifers and hydraulic boundary conditions. In regard to the urban settings of Basel, Switzerland, flow velocities of around 1 m d(-1) delineate a marker where either down-gradient temperature deviations or heat-loads into the subsurface are more relevant. Furthermore, no direct thermal influence on groundwater resources should be expected for aquifers with groundwater thicknesses larger 10 m and when the distance of the building structure to the groundwater table is higher than around 10 m. We demonstrate that measuring temperature changes down-gradient of subsurface structures is insufficient overall to assess thermal impacts, particularly in urban areas. Moreover, in areas which are densely urbanized, and where groundwater flow velocities are low, appropriate measures for assessing thermal impacts should specifically include a quantification of heat-loads into the subsurface which result in a more diffuse thermal contamination of urban groundwater resources.
Faculties and Departments:05 Faculty of Science > Departement Umweltwissenschaften > Ehemalige Einheiten Umweltwissenschaften > Applied Geology (Huggenberger)
UniBasel Contributors:Müller, Matthias Heidulf and Huggenberger, Peter and Affolter Kast, Annette and Epting, Jannis and Scheidler, Stefan
Item Type:Article, refereed
Article Subtype:Research Article
Note:Publication type according to Uni Basel Research Database: Journal article
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Last Modified:10 Oct 2017 08:51
Deposited On:10 Oct 2017 08:51

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