Detection and quantification of local anthropogenic and regional climatic transient signals in temperature logs from Czechia and Slovenia

Abstract

The paper reports on detection and quantification of the impact of local anthropogenic structures and regional climatic changes on subsurface temperature field. The analyzed temperature records were obtained by temperature monitoring in a borehole in PragueSpořilov (Czechia) and by repeated logging of a borehole in Šempeter (Slovenia). The observed data were compared with temperatures yielded by mathematical 3D time-variable geothermal models of the boreholes' sites with the aim to decompose the observed transient component of the subsurface temperature into the part affected by construction of new buildings and other anthropogenic structures in surroundings of the boreholes and into the part affected by the ground surface temperature warming due to the surface air temperature rise. A direct human impact on the subsurface temperature warming was proved and contributions of individual anthropogenic structures to this change were evaluated. In the case of Spořilov, where the mean annual warming rate reached 0.034°C per year at the depth of 38.3 m during the period 1993-2008, it turned out that about half of the observed warming can be attributed to the air (ground) surface temperature change and half to the human activity on the surface in the immediate vicinity of the borehole. The situation is similar in Šempeter, where the effect of the recently built surface anthropogenic structures is detectable down to the depth of 80 m and the share of the anthropogenic signal on the non-stationary component of the observed subsurface temperature amounts to 30% at the depth of 50 m.

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

“…For example, Ampofo et al (2006) used numerical models to investigate the heat-load of an underground railway, whereas the heat absorbed by the earth surrounding a subway can reach up to 30% of the total heat generated by the structure. Dědeček et al (2012) showed that the present subsurface temperature field observed and monitored at two locations in Central Europe (Prague-Spořilov/Czechia and Šempeter/Slovenia) is strongly influenced both by recent regional climatic changes and by thermal effects from local anthropogenic structures. With 3D numerical simulations in transient geothermal models, they could separate the transient signals of the two sources and show that they are of a similar magnitude at the two sites they studied.…”

Investigations of the air – ground temperature coupling atlocation of the Malence borehole near Kostanjevica, SE Slovenia

“…2a). It was drilled through Quaternary clay, sand and gravel in the first 16 m, below which lies Miocene marl, which gradually becomes more clayey with depth (Rajver et al, 2006;Šafanda et al, 2007;Dědeček et al, 2013). In Figure 2a the last temperature log from August 30 th , 2011 is also presented.…”

“…Due to high specific heat of pore water, it could be as low as 0.4 • 10 6 m 2 /s (for 30 % total porosity) (Šafanda et al, 2007). Dědeček et al (2013) extracted thermal diffusivity from subsurface temperature data at Malence. They got 0.2 -0.3 • 10 -6 m 2 /s in the top 5 to 10 cm of soil and 0.5 -0.7 • 10 -6 m 2 /s within 0.1 to 10 m of the bedrock.…”

“…The first measurement results from 2003 to 2005 at MBTO were published by Rajver et al (2006). Data from a period of 2003 to 2009 and a conductive and conductive-convective heat transfer mechanisms were studied by Dědeček et al (2013).…”

Tracking the Subsurface Signal of Decadal Climate Warming to Quantify Vertical Groundwater Flow Rates

“…General groundwater flow directions are indicated by arrows (dark blue). (Davis et al, 2010;Dědeček et al, 2012;Harris & Chapman, 2007) or the effects of urbanization (Ferguson & Woodbury, 2007) or land use (Kooi, 2008;MacDougall & Beltrami, 2017) on subsurface temperatures.…”