Letter

Water balance of global aquifers revealed by groundwater footprint

Received:
Accepted:
Published online:

Abstract

Groundwater is a life-sustaining resource that supplies water to billions of people, plays a central part in irrigated agriculture and influences the health of many ecosystems1,2. Most assessments of global water resources have focused on surface water3,4,5,6, but unsustainable depletion of groundwater has recently been documented on both regional7,8 and global scales9,10,11. It remains unclear how the rate of global groundwater depletion compares to the rate of natural renewal and the supply needed to support ecosystems. Here we define the groundwater footprint (the area required to sustain groundwater use and groundwater-dependent ecosystem services) and show that humans are overexploiting groundwater in many large aquifers that are critical to agriculture, especially in Asia and North America. We estimate that the size of the global groundwater footprint is currently about 3.5 times the actual area of aquifers and that about 1.7 billion people live in areas where groundwater resources and/or groundwater-dependent ecosystems are under threat. That said, 80 per cent of aquifers have a groundwater footprint that is less than their area, meaning that the net global value is driven by a few heavily overexploited aquifers. The groundwater footprint is the first tool suitable for consistently evaluating the use, renewal and ecosystem requirements of groundwater at an aquifer scale. It can be combined with the water footprint and virtual water calculations12,13,14, and be used to assess the potential for increasing agricultural yields with renewable groundwaterref15. The method could be modified to evaluate other resources with renewal rates that are slow and spatially heterogeneous, such as fisheries, forestry or soil.

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Acknowledgements

S. Siebert, M. Jellinek, M. Lathuilliere, A. Henderson and W. Rees read or discussed earlier versions of the manuscript, which markedly improved it. T.G. was supported by the Natural Sciences and Engineering Research Council of Canada and a Canadian Institute for Advanced Research junior fellowship. Y.W. was supported by Utrecht University Focus Areas Theme ‘Earth and sustainability’.

Author information

Affiliations

  1. Department of Civil Engineering, McGill University, Montreal, Quebec H3A 0C3, Canada

    • Tom Gleeson
  2. Department of Physical Geography, Faculty of Geosciences, Utrecht University, PO Box 80115, 3508 TC Utrecht, The Netherlands

    • Yoshihide Wada
    • , Marc F. P. Bierkens
    •  & Ludovicus P. H. van Beek
  3. Deltares, PO Box 85467, 3508 AL Utrecht, The Netherlands

    • Marc F. P. Bierkens

Authors

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  2. Search for Yoshihide Wada in:

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Contributions

T.G. developed the groundwater footprint method, created the figures and wrote the paper with input from all authors. Y.W. and L.P.H.v.B. completed the analysis of groundwater consumption and hydrologic data. L.P.H.v.B., T.G. and M.F.P.B developed the environmental flow methodology. All authors discussed results and edited the paper.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Tom Gleeson.

Supplementary information

PDF files

  1. 1.

    Supplementary Information

    This file contains Supplementary Text and Data, Supplementary Figures 1-4, Supplementary Tables 1-3 and Supplementary References.

Excel files

  1. 1.

    Supplementary Data

    This file contains a table with the groundwater footprint of all aquifers. The x-y coordinates are the centroids of each aquifer polygon.

Zip files

  1. 1.

    Supplementary Data

    This zipped file contains 3 files containing data on groundwater recharge, groundwater abstraction and environmental flow. The file format is arcinfo ascii grid, spatial resolution is half a degree (i.e. 50km by 50km at the equator), temporal resolution is a year, coverage is global and units are in million cubic metres per year.

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