The Brenner Base Tunnel (BBT) is being built to connect Italy and Austria running from Fortezza to Innsbruck (55km). The southern access will link Ponte Gardena with Fortezza. As widely known, underground tunneling works may have significant impact on regional hydrogeological systems, causing a drawdown of water levels and a decrease of springs’ discharge rates. Therefore, an extended monitoring of water resources can be crucial to define the possible interference between the tunneling and the surrounding environment. The analysis presented in this paper allowed to determine the main hydrogeological regime, characterizing this portion of the Isarco valley. The hydro-chemical analysis improved the knowledge of groundwater paths, mainly characterized by low-mineralized flows, running within the shallow portion of the rock mass or in correspondence of quaternary glacial deposits and not related to the deep-water network. Finally, isotopic correlations between rain and underground water have confirmed this hydrogeological layout.