Assessing the Impact of a Heated Basement on Groundwater Temperatures in Bratislava, Slovakia

Abstract

Groundwater temperature is a useful hydrogeological parameter that is easy to measure and can provide much insight into groundwater flow systems, but can be difficult to interpret. For measuring temperature directly in the ground, dedicated specifically designed monitoring wells are recommended since conventional groundwater wells are not optimal for temperature monitoring. Multilevel monitoring of groundwater temperature is required to identify contributions of different possible heat inputs (sources) on measured temperature signals. Interpreting temperature data as a cosine function, including period, average temperature, amplitude, and phase offset, is helpful. Amplitude dampening and increasing phase shift with distance from a boundary can be used for estimation of transport parameters. Temperature measurements at different depths can be used for evaluation of unknown parameters of analytical functions by optimization of regression fits in Python. These estimated parameters can be used to calculate temperatures at known water table depths which can be applied as a fixed transient boundary condition in MT3DMS to overcome the limitations of MT3DMS heat transport modeling in the unsaturated zone. In this study, temperature monitoring and modeling was used to evaluate the influence of a department store's heated basement foundation on groundwater temperature within a green space (city park), with the main outcome that 17 years after construction, the department store foundation has increased the mean groundwater temperature by 3.2 • C. Heat input evaluated by the MT3DMS model varied from 0.1 W/m 2 at a distance of 100 m up to 12 W/m 2 next to the building.

Bayesian parameter inference for shallow subsurface modeling using field data and impacts on geothermal planning

“…Structures built into the ground and the associated heat flux from these are known to impact ground temperatures, with anomalous temperatures propagating particularly far through groundwater flow (Ferguson and Woodbury, 2004; Bidarmaghz et al, 2020). Such temperature anomalies can have knock-on effects, impacting cooling and heating requirements to maintain underground spaces at comfortable levels (particularly due to groundwater not transporting away as much heat (Blum et al, 2021)), groundwater quality, and the functioning of underground biospheres (Benz et al, 2015; Attard et al, 2016; Bayer et al, 2019; Krcmar et al, 2020).…”

Impact of simplifications on numerical modelling of the shallow subsurface at city-scale and implications for shallow geothermal potential

“…The cumulative effect of these heat sources and sinks is a net-increase in underground temperatures, known as the Subsurface Urban Heat Island (SUHI). Increased subsurface temperatures can impact ventilation and cooling costs of underground spaces, efficiency of geo-energy systems, quality and quantity of groundwater flow, the health and maintenance of underground structures, and ecosystems [1][2][3][4][5][6][7][8][9][10], as well as goods production in underground spaces such as wine cellars [11]. It has been recommended that the use of increased shallow subsurface ground temperatures for energy generation could help mitigate negative impacts [12].…”

“…The scarcity of relevant data is an issue present in a number of studies modelling the subsurface, often resulting in the need to employ modelling sim-plifications (in combination with reducing computational complexity), such as of feature geometry (e.g. basements) or of the modelling of hydrology, to name but a few [1,9,[32][33][34][35][36][37][38][39]. In particular, one aspect that has not been subject to extensive investigation is the impact of surface elevation at city-scale modelling, as in most cases a flat surface is assumed for simplicity.…”

The Great Subterranean Spring of Minneapolis, Minnesota, USA, and the Potential Impact of Subsurface Urban Heat Islands

“…In the case of Schieks Cave, the groundwater direction in the shallow Quaternary aquifer indicates flow from the west, through the heavily commercialized Nicollet Mall and the densest skyscraper cluster, towards the cave (Kanivetsky, 1989). The source of the heat is likely due to heated buildings as was shown by Krcmar et al (2020), who reported groundwater temperatures had risen 3.2 K by flowing past a building in Bratislava, Slovakia.…”