Piezometric levels in the Piedmont plain (NW Italy): Trend and hydrodynamic behaviour of the shallow aquifer

This paper aims to evaluate the presence of a trend for piezometric level and precipitation in the Piedmont plain (NW Italy). Moreover, it wants to highlight some factors that can influence the piezometric fluctuation in this area. The trend analysis of precipitation and piezometric levels of the shallow unconfined aquifer in Piedmont plain was conducted, through the analysis of time series in 37 piezometers over the last 16 years (2002-2017). The trend analyses indicated that both precipitation and about half of the piezometers show no trend. Moreover, the correlation analysis between cumulative annual rainfall and average annual piezometric level showed a strong correlation in about 25% of the piezometers. The study of hydrodynamic behaviour of groundwater table suggested that, in addition to the impact of precipitation in some areas, other factors influence the groundwater level fluctuations. The analyses of time series of piezometric level permitted to identify three main factors, besides precipitation, such as: 1) changes in surface water levels 2) groundwater withdrawal 3) irrigation.