Résumé
Although the number of global water stable isotope databases (delta 18O and delta 2H) is growing, accessible groundwater stable isotope data on developing countries (e.g., Iran), are conspicuously lacking. To fill this gap, we conducted a sampling campaign during October 2023 to measure delta 18O and delta 2H in 202 wells, springs, and qanats across 10 main aquifers in Iran. We also calculated the second-order water isotopic variables, namely deuterium-excess (D-excess) and line-conditioned excess (LC-excess), in the studied aquifers, which provide insight into precipitation production and dynamics. Additionally, we determined the local meteoric water line (LMWL) for each aquifer. delta 2H, delta 18O, D-excess, and LC-excess values in the studied aquifers varied from -79.21 to -27.81 (parts per thousand), -11.95 to -4.68 (parts per thousand), -5.99 to 24.26 (parts per thousand), and -8.18 to 4.37 (parts per thousand), respectively. Eight out of the 10 calculated LMWLs for the studied aquifers had a lower slope than the global meteoric water line. Our dataset offers new insights into hydro-meteorological and pollution pathways in the studied aquifers, which supply the water needs for over half of Iran's population.