Quantifying the influence of subsurface constructions on groundwater temperature - underground and suburban railway tunnel, subterranean garage and cellar - Vortrag entfällt
O 14.4 in Urban hydrogeology
15.04.2016, 14:30-14:45, Audimax B, Geb. 30.95
The groundwater temperature field beneath urban areas is significantly different from that of the surrounding rural areas. Possible reasons for the anomalous groundwater temperatures include climatic forcing, changes in surface cover, variations in thermal conductivity of soil as well as groundwater use. Additionally the extension of subsurface infrastructures and the diffuse heat input of buildings can affect elevated groundwater temperatures in the urban areas (Menberg et al. 2013). Hot spots of up to 6 K above the average rural groundwater temperature were observed in Munich. Such significant temperature changes clearly impact the groundwater quality because of changes to subsurface biogeochemical reactions. On the other hand, the additional heat to the subsurface may also have an impact on shallow geothermal energy resource. An increase of up to 3 K in groundwater temperature can produce a remarkable improvement both in the output and efficiency of a shallow geothermal system (Allen et al. 2003). The concept of this investigation is based on (1) the characterization of the present thermal state of the groundwater body of Munich, and (2) the evaluation of the individual role of the driving factors that stimulate warming of urban aquifers. Our main interests are to clarify the thermal influence of every relevant subterranean construction on the spatial and temporal groundwater temperature distribution in Munich and to calculate the total heat flow from the constructions to the aquifer which can be utilized to generate low enthalpy geothermal energy. The investigations focus on the effects of various (i) groundwater flow velocities, (ii) heating rates, and (iii) groundwater table depths below buildings on the heat input of buildings to the aquifer. In this study the thermal influence of subsurface constructions on the urban groundwater body of Munich was examined through (1) laboratory-heat-flow-tank-experiments, (2) 3-D numerical groundwater flow and heat transport modeling and scenario development, as well as (3) deep oriented groundwater temperature monitoring to determine the magnitude, extent and timing of development of associated subsurface temperature anomalies. The results of this study are used to generate suitable numerical groundwater models of Munich city and thus to offer an extensive groundwater management concept for the sustainable thermal use of an urban groundwater system.
Allen, A., Milenic, D. & Sikora, P. (2003): Shallow gravel aquifers and the urban ʻheat islandʼ effect: a source of low enthalpy geothermal energy. ˗ Geothermics, 32(4-6): 569-578.
Menberg, K., Bayer, P., Zosseder, K., Rumohr, S. & Blum, P. (2013): Subsurface urban heat islands in German cities. - Science of the Total Environment, 442: 123-133.
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