Water resources sustainability in a globalizing world: who uses the water?

If a tonne of corn is grown in Illinois but consumed in China, is the water used to grow the corn used by the farmer in Illinois or by the consumer in China? This may come across as a philosophical or polemical question, but in an increasingly globalized world, answering this fundamental attribution question is of critical importance for addressing the issue of water resources sustainability.

Two major frameworks &ndash the freshwater planetary boundary and the water footprint &ndash have emerged over the past decade to advance our understanding of the sustainability of global freshwater resources. The freshwater planetary boundary quantifies the volume of &lsquoblue&rsquo water resources (i.e. water in freshwater lakes, rivers and aquifers) that humanity can withdraw and still remain within a presumed, safe ecological operating space (Rockström et al., 2009a). On the other hand, the water footprint concept measures humanity’s sourcing and use of all freshwater sources [i.e. blue, &lsquogreen&rsquo (precipitation that evaporates or transpires through plants) and &lsquogrey&rsquo (water required to dilute pollutants)], explicitly recognizing geographical distinctions between production and consumption regions (Hoekstra and Mekonnen, 2012a). Both frameworks strive to quantify the sustainable appropriation of water resources by humanity. The main distinction between the two approaches is in the attribution of final water &lsquouse&rsquo: The planetary boundary concept attributes use at the point of withdrawal, while the water footprint concept attributes use to the consumer, who may be spatially distinct, yet connected through national, regional and global trade networks. This inconsistency obscures our understanding of human appropriation of freshwater resources and the assignment of responsibility for the stewardship of the water and thus hinders advancement towards sustainable allocation of water resources, especially in a globalized world in which the points of withdrawal and consumption could be as far apart as Illinois and China. Here, we suggest avenues to overcome these inconsistencies, based on ideas from socio‐hydrology (Sivapalan et al., 2012 Montanari et al., 2013).