Abstract

The vulnerability of groundwater to contamination is closely related to its age. Groundwaters that infiltrated prior to the Holocene have been documented in many aquifers and are widely assumed to be unaffected by modern contamination. However, the global prevalence of these ‘fossil’ groundwaters and their vulnerability to modern-era pollutants remain unclear. Here we analyse groundwater carbon isotope data (12C, 13C, 14C) from 6,455 wells around the globe. We show that fossil groundwaters comprise a large share (42–85%) of total aquifer storage in the upper 1 km of the crust, and the majority of waters pumped from wells deeper than 250 m. However, half of the wells in our study that are dominated by fossil groundwater also contain detectable levels of tritium, indicating the presence of much younger, decadal-age waters and suggesting that contemporary contaminants may be able to reach deep wells that tap fossil aquifers. We conclude that water quality risk should be considered along with sustainable use when managing fossil groundwater resources.

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Acknowledgements

S.J. was supported by an NSERC Discovery Grant. R.G.T. acknowledges support of the NERC-ESRC-DFID UPGro grant NE/M008932/1.

Author information

Affiliations

  1. Department of Geography, University of Calgary, Calgary, Alberta T2N 4H7, Canada

    • Scott Jasechko
  2. Water in the West, Stanford University, Stanford, California 94305, USA

    • Debra Perrone
  3. Civil and Environmental Engineering, Stanford University, Stanford, California 94305, USA

    • Debra Perrone
  4. Civil and Architectural Engineering, University of Wyoming, Laramie, Wyoming 82071, USA

    • Kevin M. Befus
  5. Department of Geological Sciences, The University of Texas at Austin, Austin, Texas 78712, USA

    • M. Bayani Cardenas
  6. Department of Civil and Geological Engineering, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5A9, Canada

    • Grant Ferguson
  7. Department of Civil Engineering and School of Earth and Ocean Sciences, University of Victoria, Victoria, British Columbia V8P 5C2, Canada

    • Tom Gleeson
  8. Geoscience Centre, University of Göttingen, Göttingen 37077, Germany

    • Elco Luijendijk
  9. Global Institute for Water Security, and School of Environment and Sustainability, University of Saskatchewan, Saskatoon, Saskatchewan S7N 3H5, Canada

    • Jeffrey J. McDonnell
  10. School of Geosciences, University of Aberdeen, Aberdeen AB24 3FX, UK

    • Jeffrey J. McDonnell
  11. Department for Forest Engineering, Resources and Management, Oregon State University, Corvallis, Oregon 97330, USA

    • Jeffrey J. McDonnell
  12. Department of Geography, University College London, London WC1E 6BT, UK

    • Richard G. Taylor
  13. International Institute for Applied Systems Analysis, Schlossplatz 1, Laxenburg A-2361, Austria

    • Yoshihide Wada
  14. Department of Physical Geography, Utrecht University, Utrecht 80115, The Netherlands

    • Yoshihide Wada
  15. Department of Environmental System Sciences, ETH Zürich, Universitätstrasse 16, CH-8092, Switzerland

    • James W. Kirchner
  16. Swiss Federal Research Institute WSL, Birmensdorf CH-8903, Switzerland

    • James W. Kirchner
  17. Department of Earth and Planetary Science, University of California, Berkeley, California 94720, USA

    • James W. Kirchner

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Contributions

S.J. and J.W.K. analysed the compiled groundwater isotope data and wrote initial drafts of the manuscript. S.J. and D.P. analysed the compiled groundwater well construction data. All authors discussed results and edited the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Scott Jasechko.

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DOI

https://doi.org/10.1038/ngeo2943

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