Groundwater temperature variations in the Turin metropolitan area (Piedmont, NW Italy): what is the future?

Monitoring the qualitative and quantitative state of groundwater is a fundamental tool for investigating and preventing the effects of climate change and anthropic activities on water resources. This study represents the first investigation into the dependency of shallow groundwater temperature (GWT) on climate variability in the Turin metropolitan area (Piedmont, NW Italy).

First, a study of GWT and air temperature (AT) data on a regional scale in the time period 2010-2019 was carried out in order to understand the relationship between the two temperatures. It was possible to observe that GWT shows a general increase throughout the Piedmont Po plain, with a mean rise of 0.85 °C/10 years while AT has a mean increase of 1.69 °C/10 years.

Given these results, a 3D groundwater flow and heat transport model for the Turin metropolitan area (approximately 130 km²) has been developed using the Smoker/Heatflow numerical code. For building the model 2 different measurement campaigns of GWT in the area has been carried out during 2022.
The objective of the modelling was to better understand flow and heat transport dynamics in the shallow aquifer; moreover, a further aim was to analyse how climate change and the urban heat island of the city influences GWT, also from a forecasting perspective.

Following calibration of the model with the available data, future predictions has been made using AT data from different IPCC scenarios for the city of Turin. It has been chosen to use RCP 4.5 and RCP 8.5. The results showed for the RCP 4.5 scenario, the maximum GWT reached is 17.9 °C with an average increase of 1°C from 2022 to 2099; for the RCP 8.5 scenario the maximum GWT reached is 19.2°C with an average increase of 1.5°C from 2022 to 2099.

The development and application of this model has made possible to simulate variations in GWT on a local and city-scale in order to better understand how urban GWT will respond to the different climate scenarios in the perspective of better future management of the resource.