Mixed Recharge and Epikarst Role in a Complex Metamorphic Karst Aquifer: The Pollaccia System, Apuan Alps (Tuscany, Italy)

The Apuan Alps (Italy) are an internationally renowned karst region where several springs have a mean discharge exceeding 100 L/s, thus representing important water resources. One of the major springs, Pollaccia, was monitored for approximately one year. This spring drains structurally complex metamorphic aquifer that is characterized by multiple hydrologic sectors with variable recharge and infiltration styles. Spring discharge, temperature, electrical conductivity were compared to precipitation data, time lag analysis performed on 27 storm hydro/thermo/chemographs (HTC-graphs) occurred in different hydrological phases. A marked seasonality observed all parameters measured lags. comparison HTC-graphs no phases permitted recognition differential contribution various sectors. Pollaccia’s hydrodynamic behavior related three scenarios area: (1) allogenic runoff noncarbonate sectors; (2) autogenic over steeply dipping marble outcrops, fast epiphreatic flow through master conduits low epikarst storage; (3) highly fractured, gently quick hydraulic pressure transfer phreatic zone relevant storage.