Sarah Dickin McMaster University, Canada Refining the water footprint concept to account for non- renewable water resources Discussion Paper 1303 January 2013 This article outlines the rationale for further refinement of the water footprint concept. The author shows that the current classification system does not distinguish between renewable and non- renewable sources. Incorporating this issue would improve the water footprint as a sustainability measure and, therefore, better inform consumer choice. The Global Water Forum publishes a series of discussion papers to share the insights and knowledge contained within our online articles. The articles are contributed by experts in the field and provide original academic research; unique, informed insights and arguments; evaluations of water policies and projects; as well as concise overviews and explanations of complex topics. We encourage our readers to engage in discussion with our contributing authors through the GWF website. Keywords: Water footprint, non- renewable water, groundwater, water use, food, agriculture, irrigation With the slogan the world is thirsty because we are hungry, World Water Day 2012 brought widespread attention to water and food security challenges. For instance, the water footprint concept was used to highlight the large amount of water required for food production: 1 hamburger uses 2400 L of water, 1 apple uses 70 L, 1 cup of coffee uses 140 L. A consumer learning that tea only requires 34 L of water to produce might feel compelled to choose tea over coffee. However, the environmental implications of a water footprint value vary greatly depending on the geography of the region where the food is produced. For example, in the production of 1 kg of wheat in Canada 99.6% of the water input is rain, compared with only 30.3% in Pakistan. 1 Because of this, water footprint inputs are divided into categories of blue water and green water, to differentiate between the surface and groundwater component and the rainfall component respectively. 2 However, the sources of blue water used for irrigation differ widely around the globe, Suggested Citation: Dickin, S. 2013, Refining the water footprint concept to account for non- renewable resources GWF Discussion Paper 1303, Global Water Forum, Canberra, Australia. Available online at: http://www.globalwaterforum.org/2013/01/20/refining- the- water- footprint- concept- to- account- for- non- renewable- water- resources/
ranging from quickly recharged aquifers such as the Amazon basin, to groundwater aquifers like the Ogallala, consisting of fossil water. Fossil water aquifers are a non-renewable water source, which were recharged during more humid climatic conditions in the past. 3 While fossil fuels may be replaced by new forms of energy, once finite aquifers are depleted alternative water resources will be needed. Furthermore, over-extraction of water for irrigation reduces river flows in many basins, which can impact groundwater recharge. This disparity in groundwater availability has significant implications for food production globally. 4 In light of this, a growing body of research is focused on describing the spatial and temporal patterns of groundwater depletion, through methods including ground-based monitoring, modeling, and satellites. 5,6,7 With increased ways to measure groundwater flows, this information should be used to refine the water footprint concept to emphasize the renewable or nonrenewable components. A groundwater footprint approach was recently described, which can be used to detect unsustainable use of a groundwater aquifer. 8 A ratio of groundwater footprint to aquifer area much larger than 1 indicates that the water resource is being depleted faster than it is replenished. This information can be used to identify the renewable and nonrenewable components of many food products. In China, the largest wheat producer globally, 1 kg of wheat production requires 820 L of rainwater and 466 L of surface or groundwater on average. 1 However, the Northern China and North China plain aquifers, located in an important grain producing area, have an unsustainable groundwater footprint. 8 This means that the 466 L of blue water used in producing 1 kg of wheat in this region are non-renewable. In India, the world s second largest wheat producer, 635 L and 1173 L of green and blue water are needed respectively 1. India is home to the Upper Ganges aquifer, which has the largest groundwater footprint to aquifer area ratio, indicating groundwater mining. 8 Like the previous example, this means 1173 L of water used to produce 1 kg wheat in the Upper Ganges region is currently non-renewable. While sustainable water use is critical in all parts of the world, quantifying the litres of non-renewable water required for irrigation and manufacturing is a more effective way to bring attention to the water stress associated with food production in some regions. The distinction between renewable and nonrenewable water footprint components could also inform calculations of virtual water. Virtual water refers to water transferred to
other countries through trade in agricultural goods 9, and may consist of non-renewable or renewable components depending on the source. With growing concerns over water security, non-renewable groundwater used for irrigation in regions exporting food products should be considered in virtual water estimations, as it is much more environmentally costly than an area utilizing renewable groundwater resources. For waterintensive goods such as tomatoes, this non renewable virtual water could be used to pass higher costs on to the consumer for a product requiring a high input from an unsustainable source. Conversely, the groundwater footprint to area ratio for aquifers in Brazil, the largest producer of coffee, indicates that water input is generally renewable. Growing coffee in this region is rainfed 10, and the production process relies on water input from renewable groundwater aquifers. In addition, the volume of grey water needed to absorb pollutants created during production is renewable. While there are still environmental implications associated with producing coffee in this region, the water footprint should be described as renewable to clearly differentiate it from products depleting finite water resources. This would allow consumers to make more informed choices that promote sustainable water use. With a growing population, increasing demands for water-intensive meat products, and climate change threatening aquifer recharge, stress on groundwater resources will continue to grow. The water footprint concept brings critical awareness to the link between global consumption and freshwater scarcity. As it becomes easier to accurately monitor patterns of non-renewable water use in food production, the concept can be refined to bring awareness to groundwater depletion, such as through consideration in virtual water estimates. Similar to how a carbon footprint is advertised on some products, a nonrenewable water footprint could be added to a product packaging to build awareness of the associated impact. Further, refining the water footprint to describe renewable and nonrenewable components improves the capacity of the calculation to inform water policy and management choices that protect future water and food security. References 1. Mekonnen, M. M. and A. Y. Hoekstra (2010), A global and high-resolution assessment of the green, blue and grey water footprint of wheat, Hydrology and Earth System Sciences, 14, pp. 1259 1276. 2. Mekonnen, M.M. and Hoekstra, A.Y. (2010), The green, blue and grey water footprint of crops and derived crop products, Value of Water Research Report Series, No. 47, UNESCO-IHE: Delft, the Netherlands.
3. Williams, N. (2010), Hidden global trade in water, Current Biology, 20(9), pp.r385-r386, 4. Postel, S.L. (2000), Entering an era of water scarcity: the challenges ahead, Ecological applications, 10(4), pp. 941 948. 5. Hoekstra, A.Y., Mekonnen, M. M., Chapagain, A. K., Mathews, R.E. and B.D. Richter (2012), Global Monthly Water Scarcity: Blue Water Footprints versus Blue Water Availability, PLoS ONE 7(2), e32688. 6. Scanlon, B. R., Longuevergne, L. and D. Long (2012), Ground referencing GRACE satellite estimates of groundwater storage changes in the California Central Valley, USA, Water Resources Research, 48, W04520. 7. Moore, S. and J. B. Fisher (2012) Challenges and Opportunities in GRACE-Based Groundwater Storage Assessment and Management: An Example from Yemen, Water Resources Management, 26, pp. 1425 1453. 8. Gleeson, T., Wada, Y., Bierkens, M. F. P. and L. P. H. van Beek (2012), Water balance of global aquifers revealed by groundwater footprint, Nature, 488, pp. 197 200. 9. Allan, J. A. (2003), Virtual water the water, food, and trade nexus: Useful concept or misleading metaphor?, Water International, 28(1), pp.106 113. 10. Chapagain, A. K. and A. Y. Hoekstra (2007) The water footprint of coffee and tea consumption in the Netherlands, Ecological Economics, 64, pp. 109-118. About the author Sarah Dickin is a PhD candidate in the School of Geography and Earth Sciences at McMaster University. She is also part of a collaborative graduate program with the United Nations University Institute for Water, Environment and Health. Her research focuses on vulnerability to water-related hazards of global environmental change. Sarah can be contacted at dickinsk@mcmaster.ca About the Global Water Forum The Global Water Forum (GWF) is an initiative of the UNESCO Chair in Water Economics and Transboundary Governance at the Australian National University. The GWF presents knowledge and insights from leading water researchers and practitioners. The contributions generate accessible and evidence-based insights towards understanding and addressing local, regional, and global water challenges. The principal objectives of the site are to: support capacity building through knowledge sharing; provide a means for informed, unbiased discussion of potentially contentious issues; and, provide a means for discussion of important issues that receive less attention than they deserve. To reach these goals, the GWF seeks to: present fact and evidence-based insights; make the results of academic research freely available to those outside of academia; investigate a broad range of issues within water management; and, provide a more in-depth analysis than is commonly found in public media. If you are interested in learning more about the GWF or wish to make a contribution, please visit the site at www.globalwaterforum.org or contact the editors at editor@globalwaterforum.org. The views expressed in this article belong to the individual authors and do not represent the views of the Global Water Forum, the UNESCO Chair in Water Economics and Transboundary Water Governance, UNESCO, the Australian National University, or any of the institutions to which the authors are associated. Please see the Global Water Forum terms and conditions here. Copyright 2012 Global Water Forum.
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