@article{b9fdc68a34774f7cb3936e67733b9702,
title = "Defining the Bounds of Using Radioactive Isotope Tracers to Sense Past Groundwater Recharge Under Transient State Conditions",
abstract = "Analyzing groundwater systems in transient state is essential for understanding the response of groundwater recharge to changing environments. Radioactive isotopes have long been used to track recharge behavior, typically under steady state conditions. This study tests the limitations of using radioactive isotopes in confined aquifers and under transient conditions to sense changes in groundwater recharge rates over time. Four system parameters determine the bounds of this approach: the isotope half-life, the P{\'e}clet number (Pe), and mobile-immobile zone interactions. This study revealed that in confined groundwater systems where Pe ≥ 10, isotopes reflect transience when the half-life matches the water travel time down the flow path or the time elapsed from the change in velocity. This response is evident regardless of mobile-immobile interaction, suggesting that appropriate isotope selection is key to establishing past recharge regardless of aquifer lithology or geometry.",
keywords = "climate change, environmental tracers, groundwater, groundwater transience, recharge",
author = "M. Chmielarski and S. Dogramaci and Cook, {P. G.} and McCallum, {J. L.}",
note = "Funding Information: The Australian Research Council and Rio Tinto Iron Ore (DE180101518) supported this research. A University Postgraduate Award from The University of Western Australia supported M. Chmielarski. The authors would also like to thank Dr. Paolo Trinchero, Jennifer Gleeson, Luke Smith, Lu Li, and one anonymous reviewer for their helpful comments on developing the final manuscript. Open access publishing facilitated by The University of Western Australia, as part of the Wiley ‐ The University of Western Australia agreement via the Council of Australian University Librarians. Funding Information: The Australian Research Council and Rio Tinto Iron Ore (DE180101518) supported this research. A University Postgraduate Award from The University of Western Australia supported M. Chmielarski. The authors would also like to thank Dr. Paolo Trinchero, Jennifer Gleeson, Luke Smith, Lu Li, and one anonymous reviewer for their helpful comments on developing the final manuscript. Open access publishing facilitated by The University of Western Australia, as part of the Wiley - The University of Western Australia agreement via the Council of Australian University Librarians. Publisher Copyright: {\textcopyright} 2022. The Authors.",
year = "2022",
month = dec,
day = "16",
doi = "10.1029/2021GL096570",
language = "English",
volume = "49",
journal = "Geophysical Research Letters",
issn = "0094-8276",
publisher = "American Geophysical Union",
number = "23",
}