​Groundwater resources are the main water supply source of Madeira Island, thus the characterization of the main hydro-geological mechanisms is vital for their sustainable management. Through the present study, a large hydrochemical dataset was analyzed by traditional and PCA analysis in light of the conceptual hydrogeological model of the island. Groundwater is mainly characterized by being low mineralized (mean EC = 128.6 µS/cm), cold (mean temperature = 13.4 °C) and slightly acidic (mean pH = 6.7). Springs draining local and small perched aquifer have low solute content and local flow path, while drilled wells, tapped in the basal aquifer near the coast, are more mineralized. Groundwaters are of the Na–HCO₃, Mg–HCO₃⁻, Ca–HCO₃⁻ and Na–Cl types. The latter is found in some springs and in a few drilled wells. The hydrogeochemical

and principal component analysis identify silicate weathering process as the most important factor involved in groundwater mineralization, as also CO₂ dissolution and seawater spraying. Based on the 3H levels, most groundwaters have a significant component of modern recharge. Springs correspond to young waters, whilst waters in tunnels/galleries and drilled wells are mixtures of modern and submodern waters. The lower ³H concentration in these waters indicates longer residence time in the aquifers than spring water with higher levels and recent recharge. In general, flow paths are local and shallow. The interpretation of the chemical data in conjunction with ³H and δ¹⁸O data is in line with the conceptual model of Madeira Island proposed by Prada et al. (Comun Inst Geol Min 90:125–142, 2003; J Hydrol 536:409–425, 2016).