Managed Aquifer Recharge for sustainable groundwater use in the Cuneo Plain: from data analysis to numerical modelling

The Cuneo Plain (Piedmont, NW Italy), like all the Po Plain, is characterized by intense agricultural activities that heavily rely on seasonal water availability, which is now challenged by the climate crisis. In particular, the increased vulnerability to frequent drought emergencies is demonstrated by losses in agricultural yields. Consequently, groundwater resources have been a great tool to buffer temporary water scarcity and mitigate the drought risk. Groundwater irrigation, however, can prove to be a maladaptation practice if local aquifers are overexploited. For this reason, the assessment of the groundwater stress in the Cuneo Plain was carried out with innovative methodologies. As a result, a significant depletion was recognized, therefore, Managed Aquifer Recharge (MAR) is presented as possible solution, as it allows to convey into the subsoil, during winter times, the water in excess coming from the surrounding streams and recover it downstream through the historical drainage trenches present on site, known as "fontanili", during summertime, when the irrigation demand peaks. The objective of this work is that of estimating the temporal anomaly of the saturated thickness, by means of satellite measurements of gravimetric anomalies (from GRACE Missions) combined with hydrological models (GLDAS), as well as modelling the agricultural drainage trenches and evaluating the possible benefits coming from pilot MAR sites. This innovative practice is gaining a foothold in those territories highly vulnerable to drought risk, as is allows to store a significant amount of water underground for its use during the periods of the year characterized by higher stress and irrigation demand. In order to evaluate the advantages of this solution, numerical modelling has been exploited to understand the connections between a drainage trench and a MAR site with the unconfined aquifer system. On one hand, the fontanili were constructed starting from the XI century with the aim of reclaiming swamps through the lowering of the water table and to provide water for irrigation and drinking purposes. Nowadays, they still own a central role in the supply of irrigation water to the vast agricultural lands. By means of a conceptual model, the relationship between the depth to groundwater and their discharge was established, as well as the contribution of a peculiar configuration including screened boreholes, known as "tubi calandra", along the furrows. On the other hand, a pilot MAR site is being planned in the town of Tetti Pesio (CN), a few hundred meters upstream the fontanili. Therefore, the simulation was expanded to evaluate the effect of MAR on the water table and on the discharge of the fontanili located downstream. This work of thesis is part of the SeTe project, funded by the European Union cross-border cooperation program Interreg ALCOTRA, which aims at mitigating the drought risk by means of “sustainable blue infrastructures”.