Hydrogeology of conglomerate fractured-rock aquifers: an example from the Portofino's Promontory (Italy)

Abstract

The Portofino promontory is characterised by springs supplying Camogli, Portofino and Santa Margherita Ligure towns. This research concerns a hydrogeological preliminary study of the Caselle springs, located in the San Fruttuoso valley at 325 m asl.Water circulation occurs in discontinuities of Portofino Conglomerate and has been investigated by scientific studies since the late Nineteenth Century. The flow of Caselle springs has been monitored, while the climatic parameters recorded in the Mount Portofino weather station have allowed a first comparison between rains and outflows.The hydrogeological water balance has allowed assessing a loss due to evapotranspiration of 627 mm and an outflow of 753 mm. The evaluation of the recharge area permitted to calculate outflows between 4 and 13 l/s: adopting an infiltration rate of 0.7, obtained infiltration values are comparable with the measured flow rates. The answer to the rains of hydrogeological parameters shows a ground-water velocity of 10-6 m/s; protecting the aquifer from potential sources of pollution is therefore deemed as essential, taking into account that over 80,000 hikers per year walk upon the recharge area.