Hydrology

Supply and demand

A Correction to this article was published on 01 October 2012

With a global population of over seven billion and growing, the demand for natural resources has never been greater. If future requirements for food and water are to be met, the Earth's resources must be used sustainably.

Attempts to manage the world's natural resources have led to the development of a number of sustainability measures. The ecological footprint, for instance, denotes the area of land required to sustain a population.

As with land, groundwater has become scarcer; extraction has increased sharply in recent decades to meet the domestic, industrial and agricultural needs of billions of people. As a result, groundwater levels have fallen in many parts of the world, particularly in regions where surface water supplies are sporadic or sparse. This has lead to mounting concerns about the sustainability of groundwater supplies.

Credit: © ISTOCKPHOTO/THINKSTOCK

Using a global hydrological model and previously published estimates of groundwater consumption, Tom Gleeson and colleagues have estimated the global groundwater footprint — that is, the aquifer area required to sustain current rates of groundwater consumption and aquifer ecosystem services (Nature 488, 197–200; 2012). According to their calculations, the global groundwater footprint exceeds the area of hydrologically active aquifers by 3.5 times.

A spatially explicit analysis of individual aquifers reveals that this unsustainable exploitation of global groundwater resources is driven by abstraction in a few agriculturally important aquifers, primarily in Asia and North America. According to this analysis, around 1.7 billion people live in regions where groundwater use is unsustainable. Of those living in regions of groundwater stress, around 60% reside in India and China.

The concept of a groundwater footprint as devised by Gleeson et al. could prove instructive when it comes to agricultural planning and water management strategies. A number of regions where agricultural yields could be improved, for instance, coincide with regions where aquifers are being used sustainably. And, by way of example, Gleeson et al. note that the transfer of just a small percentage of groundwater consumption from the Upper to the Lower Ganges in India could diminish, although not remove, groundwater stress in the region.

It is clear that current patterns of groundwater use in a number of agriculturally intensive regions of the world are not sustainable. Now that the problem has been identified and investigated quantitatively, it is time to act.

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Armstrong, A. Supply and demand. Nature Geosci 5, 592 (2012). https://doi.org/10.1038/ngeo1569

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