Environmental isotopes (δ2H, δ13C, δ18O, 3H, and 14C) as a diagnostic tool in the appraisal of mineral water management and protection: two case studies-Portugal

Groundwater management and protection must be confronted under ethical and moral concerns, with regulations and water policies for proper and sustainable civilization development. Approximately half of the world population relies on groundwater as the main source of supply, representing a vital requirement for human life and progress. Often in many regions of the world, water authorities are facing scarcity and over-exploitation of the available fresh water reserves. In these circumstances, geoethical aims to represent a way to reach the entire community (water authorities, stakeholders, scientists, and the population in general), focusing on the importance and awareness of water sustainability. In this paper, two case studies from Portugal will be reviewed and discussed aiming to highlight the importance of isotope hydrology as a way to obtain a unique characterization of groundwater resources foreseeing a proper management and sustainability of the groundwater systems. The first case study, Melgaco-Messegaes CO2-rich mineral waters, is located in a granitic environment (NW Portugal). The study allowed to establish the preferential recharge altitude (delimitation of protection limits) based on the & delta;H-2 and & delta;O-18 content; the H-3 data indicates a mean residence time of 40 years; the carbon isotopes (& delta;C-13 and C-14 values) highlight methanogenesis and/or mantle-derived carbon as the main carbon source. In the second case study, Moura-Ficalho aquifer (carbonate formations, SE of Portugal), the combined use of geochemical and isotopic (stable and radioactive) data allowed the identification of different (much smaller) flow velocities in the deepest layers of the Moura-Ficalho aquifer and the & delta;O-18 data indicates recharge under different climate conditions.