How Climate Change influence groundwater temperature? A case study in the Piedmont Po Plain (NW Italy)

This study represents the first regional-scale investigation in the Piedmont Po plain about the relationship between groundwater temperature in the shallow aquifer (GWT) and climate variability.
The aim of this investigation is to study and compare time trends in air temperature (AT) and GWT over a 10-year time period (between 2010 and 2019), and to evaluate possible relationships between the two parameters. For doing so we had used daily measures taken from 41 monitoring wells located in the shallow aquifer and 20 weather stations throughout the Piedmont Po plain area.

Both AT and GWT showed an increase over the observed period with a more pronounced growth of the AT. With regard to AT all the weather stations had shown an increasing trend with a variation in the annual mean 1.7 and 2.2 ^◦C/10 years; moreover, GWT annual mean generally shows a variation between −0.3 and 2.1 ^◦C/10 years. This result allows to state that GWT is more resilient to climate change than AT. However, some monitoring wells in the study area showed a behaviour that partially deviated from the standard trend observed for the majority of the region: these wells were influenced by particular anthropic factors (for example the paddy fields) or natural elements (as the monitoring wells located downstream of melting glaciers, or the wells located close to Rivers). Further investigations will be conducted in future in Piedmont plain areas with different behaviour, in order to better understand their dynamics and the factors that may influence GWT and how they are affected by climate change.

Moreover, this study wanted to stress the importance of the knowledge of the localization in wells of the instruments for the GWT measurement, to have the most accurate and comparable data. As already state in literature the GWT fluctuation in the bottom part of the aquifer was milder than the fluctuation observed in the most superficial part. Therefore, it has been possible to observe that in the study area when the depth of the instrument increased, the maximum and minimum peaks of the GWT shifted in time respect to the maximum and minimum peaks of the AT.

Lastly, we are conducting a groundwater and heat flow simulation of the shallow aquifer of the Turin Plain area using a numerical model with Smoker Heatflow code. The calibration performed with the available hydrogeological setting information of the area and the GWT and AT data will allow us to model the future spatial distribution of GWT in the study area, according to the IPCC forecast scenarios.