Vulnerability of coastal aquifers to groundwater use and climate change

Abstract

Climate change and human population growth are expected to have substantial impacts on global water resources throughout the twenty-first century1,2. Coastal aquifers are a nexus3 of the world’s oceanic and hydrologic ecosystems and provide a water source for the more than one billion people living in coastal regions4,5. Saltwater intrusion caused by excessive groundwater extraction is already impacting diverse regions of the globe5,6,7. Synthesis studies8,9 and detailed simulations10,11,12,13 have predicted that rising sea levels could negatively impact coastal aquifers through saltwater intrusion and/or inundation of coastal regions. However, the relative vulnerability of coastal aquifers to groundwater extraction and sea-level rise has not been systematically examined. Here we show that coastal aquifers are more vulnerable to groundwater extraction than to predicted sea-level rise under a wide range of hydrogeologic conditions and population densities. Only aquifers with very low hydraulic gradients are more vulnerable to sea-level rise and these regions will be impacted by saltwater inundation before saltwater intrusion. Human water use is a key driver in the hydrology of coastal aquifers, and efforts to adapt to sea-level rise at the expense of better water management are misguided.

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Figure 1: Coastal aquifers are affected both by groundwater extraction and sea-level rise.
Figure 2: Present saltwater intrusion areas have a high population density and/or low hydraulic gradients.
Figure 3: The impact of groundwater extraction on coastal aquifers is more significant than the impact of sea-level rise.
Figure 4: The uncertainty owing to different aquifer types is significant as shown by simulation of these types over a range of coastal populations.

Change history

  • 16 April 2012

    In the version of this Letter originally published online, equation (1) was incorrect. This has now been corrected in all versions of the Letter.

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Acknowledgements

M. Jellinek, L. Smith, E. Luijendijk, V. Bense and V. Gerard provided valuable advice during the writing of this manuscript. Y. Fan generously provided data on the water-table elevation. T.G. was supported by the Natural Sciences and Engineering Research Council of Canada postdoctoral fellowship and a Canadian Institute for Advanced Research junior fellowship.

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Both authors contributed to planning of this paper. G.F. carried out the analytical modelling and T.G. conducted the GIS analyses. Both authors contributed to the writing of the paper and drafting of figures.

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Correspondence to Grant Ferguson.

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The authors declare no competing financial interests.

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Ferguson, G., Gleeson, T. Vulnerability of coastal aquifers to groundwater use and climate change. Nature Clim Change 2, 342–345 (2012). https://doi.org/10.1038/nclimate1413

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