Climate impact assessment to the groundwater levels based on long time-series analysis in a paddy field area (Piedmont region, NW Italy): preliminary results

Abstract

The analysis of the time-series of groundwater level are extremely important to observe the behaviours of groundwater over time and to identify any critical situations. The studied area is an agricultural district characterised by paddy fields, located in the eastern part of Piedmont, on the border with Lombardy. In this area long time-series of groundwater level, starting from the 1960s, have been collected in 16 wells. Water table data have a good completeness (in the majority of the cases >90%). Firstly, the groundwater hydrodynamic behaviour, based on water table levels, was investigated to highlight the response of groundwater to the recharge. A basic statistical analysis was performed (mean, median, standard deviation, maximum, minima), and then trends of water table levels were evaluated in order to better observe the long-term behaviour of groundwater. These analyses allowed to observe a groundwater hydrodynamic behaviour characterised by a repeating annual pattern (minimum in February/March and maximum in August/September) in correspondence to the period of irrigation. Moreover, trend analysis highlighted the presence of both wells with a decreasing water table (with maximum lowering of 4.3 m in 60 years) and wells with an increasing water table (with maximum rises of 2.8 m in 35 years). Furthermore, in most cases, it can be observed that all three trends analysed agree on being positive or negative. Future insights will be the comparison of these long time-series with the meteorological data, and the investigation of other factors (e.g. anthropic withdrawal, variations of cultivation practices and irrigation, geology of the subsoil) to better understand the causes of the water table fluctuations and trends.