Simulation modelling for groundwater safety in an overexploitation situation: the Maggiore Valley context (Piedmont, Italy)

Abstract

The Maggiore Valley well field plays a fundamental role in supplying drinking water to a large territory of the Piedmont (North-western Italy). However an increasing water demand have led to the overexploitation of groundwater resources: this situation caused a progressive drawdown of the piezometric level (locally up to 0.8 m/year), a spatial reduction of the artesian zone, a local land subsidence and well damages. The main intent of this study is the development of a groundwater flow model of the area for analyzing the aquifer response to various pumping strategies. The groundwater flow simulation, achieved by the application of the MODFLOW code, was calibrated satisfactorily. Then the groundwater response to four scenarios was simulated, in order to suggest the best option to mitigate the problem. In three cases a withdrawal decrease of 110 l/s has been simulated, considering or not the re-location of some wells out of the well field zone of influence; moreover a significant withdrawal reduction of 150 l/s, as a result of the possible connection with the water supply of the Monferrato Aqueduct, located north of the study area, was simulated. All the simulations provide an increase of the piezometric level, even up to 30 m. Nevertheless the most promising management strategy for the Maggiore Valley well field is the connection with Monferrato Aqueduct: indeed the piezometric level rises up to 25 m without the necessity of drilling of new wells.

Effectiveness of geophysical surveys for water wells relocation in overexploited aquifers (the example of Maggiore and Traversola Valleys, Northwestern Italy)

“…Indeed, at the end of the XIX century, the piezometric levels of the Maggiore Valley wells were up to 10 m higher than the ground surface, creating the conditions for an artesian aquifer (Sacco 1924, Beretta et al 1999. Since 1920 to present, a reduction of more than 50 m in groundwater level has been observed (Lasagna et al 2014). Continuous extraction over the decades has resulted in the progressive reduction of the artesian area: at present artesian conditions prevail only in the northern sector of the aquifer (see also later Figure 3).…”

“…530 l/s). As an example, in recent years, over the period 1996 to 2009, the extraction rate increased from 13,4to 14,4 Mm 3 /year (Lasagna et al 2014).…”

Evaluation of sources and fate of nitrates in the western Po plain groundwater (Italy) using nitrogen and boron isotopes

“…Only locally, e.g. in the Poirino Plateau, the flow directions are very different (Lasagna et al 2014).…”

Hydrogeology of the western Po plain (Piedmont, NW Italy)

“…The hydrogeological map was produced in English and Italian because this study is addressed not only to an international audience of researchers, but also to public administrations, stakeholders, and local professionals working on groundwater management. More specifically, this map represents a basic step for future investigations (aquifer vulnerability, recharge areas, wellhead protection areas …) or studies aimed at solving current problems of groundwater resources in Piedmont, such as groundwater contamination (Lasagna et al, 2013(Lasagna et al, , 2015(Lasagna et al, , 2016b(Lasagna et al, , 2018Lasagna & De Luca, 2016Martinelli et al, 2018), overexploitation (De Luca et al, 2018;Lasagna et al, 2014Lasagna et al, , 2019a, piezometric level variations as response to climate change (Lasagna et al, 2019b(Lasagna et al, , 2020.…”