title: Pleistocene paleo-groundwater as a pristine fresh water resource in southern Germany--evidence from stable and radiogenic isotopes.
abstract: Shallow groundwater aquifers are often influenced by anthropogenic contaminants or increased nutrient levels. In contrast, deeper aquifers hold potentially pristine paleo-waters that are not influenced by modern recharge. They thus represent important water resources, but their recharge history is often unknown. In this study groundwater from two aquifers in southern Germany were analyzed for their hydrogen and oxygen stable isotope compositions. One sampling campaign targeted the upper aquifer that is actively recharged by modern precipitation, whereas the second campaign sampled the confined, deep Benkersandstein aquifer. The groundwater samples from both aquifers were compared to the local meteoric water line to investigate sources and conditions of groundwater recharge. In addition, the deep groundwater was dated by tritium and radiocarbon analyses. Stable and radiogenic isotope data indicate that the deep-aquifer groundwater was not part of the hydrological water cycle in the recent human history. The results show that the groundwater is older than ~20,000 years and most likely originates from isotopically depleted melt waters of the Pleistocene ice age. Today, the use of this aquifer is strictly regulated to preserve the pristine water. Clear identification of such non-renewable paleo-waters by means of isotope geochemistry will help local water authorities to enact and justify measures for conservation of these valuable resources for future generations in the context of a sustainable water management.
authors: Friedrich-Alexander-University Erlangen-Nuremberg (FAU), Department of Geography and Geosciences, GeoZentrum Nordbayern, Schlossgarten 5, 91054 Erlangen, Germany. Electronic address: robert.van.geldern@fau.de.
authors: Robert
authors: R
authors: van Geldern
authors: Friedrich-Alexander-University Erlangen-Nuremberg (FAU), Department of Geography and Geosciences, GeoZentrum Nordbayern, Schlossgarten 5, 91054 Erlangen, Germany.
authors: Alfons
authors: A
authors: Baier
authors: Friedrich-Alexander-University Erlangen-Nuremberg (FAU), Department of Geography and Geosciences, GeoZentrum Nordbayern, Schlossgarten 5, 91054 Erlangen, Germany.
authors: Hannah L
authors: HL
authors: Subert
authors: Erlanger Stadtwerke AG, Äußere Brucker Str. 33, 91052 Erlangen, Germany.
authors: Sigrid
authors: S
authors: Kowol
authors: Friedrich-Alexander-University Erlangen-Nuremberg (FAU), Department of Geography and Geosciences, GeoZentrum Nordbayern, Schlossgarten 5, 91054 Erlangen, Germany.
authors: Laura
authors: L
authors: Balk
authors: Friedrich-Alexander-University Erlangen-Nuremberg (FAU), Department of Geography and Geosciences, GeoZentrum Nordbayern, Schlossgarten 5, 91054 Erlangen, Germany.
authors: Johannes A C
authors: JAC
authors: Barth
mesh_terms: D004784:Environmental Monitoring; D005618:Fresh Water; D060587:Groundwater / Q000737:chemistry*; D062070:Hydrology; D007554:Isotopes / Q000032:analysis*; D058438:Water Cycle; D014872:Water Movements; D060753:Water Quality / Q000592:standards*; D062066:Water Resources / Q000032:analysis*
chemical_list: D007554:Isotopes
keywords: Hydrology; Keuper; Oxygen and hydrogen stable isotopes; Paleo-groundwater; Radiocarbon; Tritium