Characterizing the Recharge of Fractured Aquifers: A Case Study in a Flysch Rock Mass of the Northern Apennines (Italy)

12 springs from the northern Apennines of Italy were studied by means of a comprehensive hydrogeological investigation to unravel recharge processes taking place in a highly fractured slab of flysch rock hosting the corresponding aquifers. Several campaigns were carried out during the period 2005-2008 to gather springs' discharge together with electrical conductivity and temperature data. Water samples were collected and allowed the determination of the major ions (Ca2+, Mg2+, Na+, K+, SO42-, HCO3-, Cl-) and the isotopic content (delta O-18). Additionally, groundwater discharge from 3 selected springs was measured continuously using pressure-transducers. Over the same period, reference delta O-18 values for rainfall and snow-melt water were collected monthly by a rain-gauge. Results highlighted an aquifer-like behavior of this slab of flysch rock. The springs are characterized by a Ca-HCO3 hydro-facies and an increase of groundwater mineralization has been noticed moving toward the base of the slab; the mean discharges are between 0.3 and 0.7 l.s(-1) and suffered a marked variability during the year; the total maximum yield is about 155,000 m(3) while the total discharge volume is around 320,000 m(3).y(-1). By processing the delta O-18 isotope values from springs (mean annual values ranged from -9.67 and -10.42 parts per thousand) and by combining them with rainfalls datasets, results show that the main aliquot of recharge occurs in the winter-spring months and it is principally related to the solid precipitations (snow-melt).