The genesis and the hydrogeological features of the Turin Po Plain fontanili, typical lowland springs in Northern Italy

The fontanili are typical lowland springs that occur in Northern Italy along the transition zone from high to low plain (the “fontanili line”), due to changes in both the slope surface and the sediment grain size. These resurgences of phreatic water were investigated in the western sector of the Po Plain in the Turin Province. Although the available bibliographic data through 2005 reveal the occurrence of 111 fontanili in the study area, only 51 preserved fontanili have been identified in field surveys. The main morphological and geological features of these resurgences were recorded and entered into a database. In addition, the small-scale hydrogeologic framework of these fontanili was clarified by means of lithostratigraphic cross-sections. Taking into account the drastic decrease in the number of these particular springs, ten fontanili were selected for detailed investigation based on their state of preservation and accessibility. A geological map of each emergence was constructed to explain its origin. The main hydrochemical and physical variables and parameters were measured every month for a period of one year. Only three sources provided water throughout the entire year, and their flow rates reached 60–80 l/S during the summer due to recharge from irrigation channels. All other fontanili remained dry during different periods of the year. The hydrochemical data revealed a Ca–Mg bicarbonate composition. The electrical conductivity increased from the north (100–300 μS/cm) to the south (300–600 μS/cm), and nitrate concentrations were below the limits imposed by Italian law (50 mg/l). This study should be considered as the basis of a proposal to the local government for the protection of a subset of these springs as sites of special geological interest (geo-sites).