The use of environmental isotopic and hydrochemical tracers to characterize the functioning of karst systems in the Tlemcen Mountains, northwest Algeria

The functioning of karst systems in the Tlemcen Mountains, Algeria, was studied using environmental isotopic and chemical parameters. The weakly enriched values of O-18 suggest a fast infiltration of water through the karst systems. The deuterium (H-2) excess in groundwater and tritium (H-3) in precipitation show that the region is subjected to Mediterranean and Atlantic influences with a predominance of the former. The isotopic gradient, in combination with topographic and geologic criteria, allows the recharge areas of the main karst systems to be estimated. The results of C-13, C-14 and H-3 analysis show that the majority of present waters come from perched systems and mixture waters influenced by three clusters ("ante-thermonuclear" waters, "thermonuclear" waters, and present waters) that generally emerge from semi-confined systems. The oldest waters are relatively rare and are stored in deeply confined systems. These results are consistent with the hydrochemical and the hydrogeological findings. The results have important implications in groundwater protection.