Volumetric water footprints, applied in a global context, do not provide insight regarding water scarcity or water quality degradation
Introduction
In a recent contribution to Ecological Indicators, Hoekstra (2016) critiques the scarcity-weighted water footprint that has been proposed for use in life cycle assessments, and has been adopted by the International Organization for Standardization (ISO) as the preferred method for calculating and reporting water footprints (ISO, 2014; Pfister et al., 2015). Much of the author’s critique reflects his perspective that water scarcity is a global issue, and that water allocation across competing uses should be viewed in a global context (Hoekstra and Mekonnen, 2012, Hoekstra and Wiedmann, 2014). In particular, Hoekstra (2016) suggests that because the global demand for water is increasing, policy makers must measure and compare the pressure that all products place on the global water supply. To this end, Hoekstra (2016) proposes that the volumetric water footprint promoted by the Water Footprint Network is superior to the scarcity-weighted water footprint adopted by the ISO. He suggests also that accounting for water scarcity within river basins or in a local or regional context is not appropriate, because water use in any basin reduces the volume of water remaining for other uses at some location within the global context.
Much of the discussion in Hoekstra (2016) mischaracterizes water scarcity and its impacts on the environment, natural resources, livelihoods, and human health. My goal in this paper is to demonstrate the inaccuracies in that discussion and to describe alternative perspectives regarding water scarcity, allocation, and use in both rainfed and irrigated settings. It is not my goal to take sides in the discussion regarding which water footprint should have been adopted for use in the ISO framework. I do not assess the method for calculating the scarcity-adjusted water footprint proposed by other authors (Ridoutt and Pfister, 2010, Ridoutt and Pfister, 2013, Boulay et al., 2015a, Boulay et al., 2015b). Rather, I seek to set aside the notion that a volumetric water footprint, which does not account for water scarcity, can provide meaningful guidance regarding water policies, investments, or water allocations. Volumetric water footprints are silent on the issues that matter most in determining whether water allocations are sustainable, efficient, or equitable (Wichelns, 2015a). It is not possible to assess those issues and to determine optimal policies and investments only by calculating the volume of water consumed in a given process or chain of processes.
I endeavor also to demonstrate the importance of considering water scarcity in local and regional settings. Although water is a global resource, as described quite well by the hydrologic cycle, water scarcity is a local and regional issue. It is essential that local and regional water users and policy makers assess scarcity conditions in their domains, and implement appropriate policies, incentives, and strategies to manage water wisely. Investments in extending access to water and improving water quality also must be evaluated and implemented locally. The global perspective described by Hoekstra (2016) is incorrect. One cannot successfully address matters of water scarcity or water quality degradation without considering local or regional issues and solutions.
In sum, I describe four perspectives that contrast with those presented in Hoekstra (2016): 1) Water scarcity is not a global issue, 2) The impacts of water use vary with location and with time, 3) Irrigated agriculture cannot be replaced by improving the productivity of rainfed agriculture, and 4) Local water scarcity and water quality degradation impair the health of millions of urban and rural residents, worldwide.
Section snippets
Water scarcity is local and regional
Hoekstra (2016) suggests that because water is a global resource, water depletion also has a global character. In the author’s view, water use in any location subtracts from the sum of global water available for other uses. Thus, the environmental impact of water use in any location is the same: “Every litre of water consumption, whether in a water-rich or water-poor river basin, and whether [soil moisture, effective rainfall, surface water, or groundwater], will reduce the water volume
Water use impacts vary across locations and seasons
Hoekstra (2016) suggests that the environmental impact of water use is the same in water abundant and water scarce basins. In his view, “global water availability is the sum of the water [available] in the various basins in the world; some of them contribute a lot to overall availability, others only a little.” Hence, water withdrawals and use in any basin impact global water availability in equivalent fashion. Furthermore, the author suggests that “producing more water-intensive products where
Rainfed agriculture will not replace irrigated production
Hoekstra (2016) suggests also that improvements in the productivity of rainfed agriculture would reduce the need for irrigation, thus reducing also the scarcity of surface water and groundwater. To this end, “An essential component in solving the over-consumption of [surface water] and [groundwater] and associated environmental impacts in water-scarce areas is to use [soil moisture and effective rainfall] more productively in water-abundant areas, because if water-intensive products are
Local water scarcity impairs the health of millions
Hoekstra (2016) suggests that the attempts of some authors to assess the impacts of water scarcity on the environment and human health, using a water stress index or scarcity-adjusted measures of water footprints (Pfister et al., 2009, Ridoutt and Pfister, 2013, Hess et al., 2015) are not appropriate, as the proposed metrics have no empirical interpretation. As noted above, it is not my goal to critique the scarcity-adjusted water footprint indicators. However, the discussion put forth by
Summing up
Much of the discussion in the critique of the water-scarcity weighted water footprint, presented in Hoekstra (2016), mischaracterizes water scarcity and its impacts on the environment, natural resources, livelihoods, and human health. Water scarcity is not a global issue, but rather a local and regional issue that requires analysis, policies, and investments at those levels. Volumetric water footprints do not contain the information needed to assess water scarcity because they do not consider
Acknowledgment
I appreciate the comments of two reviewers who have helped me to clarify and enhance the discussion.
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