Impacts of climate change on groundwater: numerical modelling of a northern Apennines catchment

The objective of this study is to provide an innovative methodology for the estimation of climate change impacts on groundwater resources. This methodology has been applied to the Tresinaro stream catchment (147 km2) in the northern Apennines (Italy), and to the main water source of the stream, the Mulino delle Vene springs (Carpineti, Reggio Emilia province). These springs outflow from a fractured aquifer hosted in a sandstone plateau, and the mean discharge is 96.8 l/s. Firstly, some finite elements models of the fractured aquifer feeding the Mulino delle Vene springs have been developed, with the codes FEFLOW and TRANSIN, in order to investigate the groundwater flow system. In particular, some sensitivity analyses and transient state simulations have been carried out, and a range of calibrated conductivity values for the fractured rock masses (between 1.16 x 10-4 m/s and 1.16 x 10-7 m/s) has been identified. Moreover, a physically based surface-subsurface flow model has been developed for the Tresinaro stream catchment with the finite elements code HydroGeoSphere. In the second place, some rainfall-runoff models of the Mulino delle Vene springs have been built and calibrated on the daily springs discharge data. Then, the calibrated and validated models have been combined with climate change scenarios from five Regional Climate Models. Considering the results of this study, it is very likely that, in the next future, groundwater flow rates of the Mulino delle Vene springs will decrease, especially during the low flow period, exacerbating the water stress condition in the area (e.g. maximum discharge is likely to decrease by the 26.3% in September). The results of this analysis represent a first answer to the lack of researches in the field of climate change and groundwater in Italy. The developed methodology can be easily applied to other areas.