Bradley G. Ridoutt

A new water footprint calculation method integrating consumptive and degradative water use into a single stand-alone weighted indicator

PurposeA complete assessment of water use in life cycle assessment (LCA) involves modelling both consumptive and degradative water use. Due to the range of environmental mechanisms involved, the results are typically reported as a profile of impact category indicator results. However, there is also demand for a single score stand-alone water footprint, analogous to the carbon footprint. To facilitate single score reporting, the critical dilution volume approach has been used to express a degradative emission in terms of a theoretical water volume, sometimes referred to as grey water. This approach has not received widespread acceptance and a new approach is proposed which takes advantage of the complex fate and effects models normally employed in LCA.Methods Results for both consumptive and degradative water use are expressed in the reference unit H2Oe, enabling summation and reporting as a single stand-alone value. Consumptive water use is assessed taking into consideration the local water stress relative to the global average water stress (0.602). Concerning degradative water use, each emission is modelled separately using the ReCiPe impact assessment methodology, with results subsequently normalised, weighted and converted to the reference unit (H2Oe) by comparison to the global average value for consumptive water use (1.86 × 10−3 ReCiPe points m−3).Results and discussionThe new method, illustrated in a simplified case study, incorporates best practice in terms of life cycle impact assessment modelling for eutrophication, human and eco-toxicity, and is able to assimilate new developments relating to these and any other impact assessment models relevant to water pollution.ConclusionsThe new method enables a more comprehensive and robust assessment of degradative water use in a single score stand-alone water footprint than has been possible in the past.

Reducing humanity’s water footprint

There are limits to the extent that humanity can continue to increase its appropriation of freshwater from the natural environment. Recent discussion has centered on the notion of a safe operating limit, being the level of global freshwater use beyond which widespread irreversible environmental change and harmful impacts on human well being are threatened (1). However, the issue is not only about planetary environmental boundaries, but also about equity, with consumption patterns in developed countries, underpinned by global supply chains, blamed for taking advantage of a disproportionate share of the Earth’s scarce freshwater resources. Water use models have produced estimates of global freshwater withdrawals of 3594 and 3824 km3 yr-1, representing the situation in 1995 and 2000, respectively (2, 3). Other authors estimate current withdrawals at around 4000 km3 yr-1, with around 2600 km3 yr-1 (65%) being consumptive use whereby water is removed from the local hydrological system by such processes as evaporation and crop transpiration (1). With a proposed planetary boundary of 4000 km3 yr-1 of consumptive surface and groundwater use (with a zone of uncertainty of 4000-6000 km3 yr-1), it would appear that humanity’s freshwater use is currently within the safe operating limit (1). Indeed, these results suggest there may be scope for humanity’s total global freshwater withdrawals to increase and that freshwater scarcity is not such a critical issue compared to climate change, biodiversity loss, or perturbation of the global nitrogen and phosphorus cycles. However, in proposing limits for global freshwater use it is critical to also take into consideration the regional nature of freshwater scarcity. For each of the 11,050 watersheds represented in the WaterGap2 model (as described in 2), we multiplied withdrawals by the local Water Stress Index (WSI) (4). The global sum we refer to as humanity’s water footprint. Somewhat alarmingly, our analysis indicated that the majority of global freshwater withdrawals are currently from watersheds already experiencing extreme water stress (WSI > 0.9, Figure 1). This concurs with reports of an estimated 25% of rivers no longer flowing reliably to the sea, large-scale regional groundwater depletion, and the observed collapse of complete freshwater systems such as the Aral Sea. Therefore, irrespective of the proposed boundaries of global freshwater use, there is an immediate need to relieve excessive pressure on those already highly stressed watersheds where freshwater resources are now being depleted and damages to ecosystems and human health are already manifest. What is deceptive about freshwater use is that the vast majority, or around 90%, is associated with the life cycles of products and services. Globally, withdrawals for the domestic sector are comparatively minor. This means that citizens consume a lot more water than they might realize and that their water footprints extend far beyond their local area and even national boundary. Due to the interconnectedness of global business, the local consumption of products and services is intervening in the hydrological cycle throughout the world and to an extent rarely understood or appreciated. As such, there has been much recent interest in the concept of water footprinting, to make transparent the impacts of consumption and production on global freshwater scarcity (5), including a new ISO work program to develop a global water footprint standard (ISO/TC207/SC5/WG8). The interest in quantifying the environmental impacts related to products and services has also emerged in the area of life cycle assessment and life cycle management, led by the UNEPSETAC Life Cycle Initiative where a working group on water use is active. The importance of water footprinting has also been recognized by such organizations as the World Business Council for Sustainable Development and the UN Global Compact. From a policy standpoint, water footprinting is creating a capacity for change which in many ways is comparable to carbon footprinting. However, fundamental to any strategy to reduce the pressure humanity exerts on freshwater systems is the need for a stabilization target, without which it is difficult for governments, businesses, and individuals to conceptualize the extent of necessary action. In terms of climate change, the concentration of carbon dioxide and * E-mail: brad.ridoutt@csiro.au. RH ON DA SA UN DE RS Environ. Sci. Technol. 2010, 44, 6019–6021

Environmental relevance—the key to understanding water footprints

Hoekstra and Mekonnen (1) offered a comprehensive assessment of global water use from the perspective of national production, consumption, and international trade. This study highlighted the often neglected fact that it is the demand for everyday goods and services that places the most pressure on the world’s freshwater systems. As such, strategies based on sustainable consumption and production are needed to reduce humanity’s burden on freshwater and to complement those strategies that operate at the watershed or water resource level.

Making sense of the minefield of footprint indicators.

Bradley Ridoutt,*,† Peter Fantke,‡ Stephan Pfister, Jane Bare, Anne-Marie Boulay, Francesco Cherubini, Rolf Frischknecht, Michael Hauschild,‡ Stefanie Hellweg, Andrew Henderson, Olivier Jolliet, Annie Levasseur, Manuele Margni, Thomas McKone, Ottar Michelsen, Llorenc Mila i Canals, Girija Page, Rana Pant, Marco Raugei, Serenella Sala, Erwan Saouter, Francesca Verones, and Thomas Wiedmann †Commonwealth Scientific and Industrial Research Organisation (CSIRO), Clayton, Victoria 3169, Australia ‡Technical University of Denmark (DTU), Department for Management Engineering, Division for Quantitative Sustainability Assessment, 2800 Kgs. Lyngby, Denmark ETH Zurich, Institute of Environmental Engineering, 8093 Zurich, Switzerland United States Environmental Protection Agency, Sustainable Technology Division, Systems Analysis Branch, National Risk Management Research Laboratory, Cincinnati, Ohio 45268, United States CIRAIG, Ecole Polytechnique de Montreal, Montreal, Canada Norwegian University of Science and Technology (NTNU), Industrial Ecology Programme, Department of Energy and Process Engineering, NO-7491 Trondheim, Norway treeze Ltd., Uster, Switzerland University of Texas Health Science Center, School of Public Health, Division of Epidemiology, Human Genetics and Environmental Sciences, Houston, Texas 77030, United States University of Michigan, School of Public Health, Environmental Health Sciences, Ann Arbor, Michigan 48109, United States University of California, Lawrence Berkeley National Laboratory and School of Public Health, Berkeley, California 94720, United States Norwegian University of Science and Technology (NTNU), Division for Finance and Property, NO-7491 Trondheim, Norway United Nations Environment Programme (UNEP), Division for Technology, Industry and Economics, 15 Rue de Milan, 75009 Paris, France University of Western Sydney, School of Science and Health, Penrith, NSW 2751, Australia European Commission, Joint Research Centre, Institute for Environment and Sustainability, Via Enrico Fermi 2749, Ispra, I-21027, Italy Oxford Brookes University, Department of Mechanical Engineering and Mathematical Sciences, Oxford OX33 1HX, United Kingdom UNSW Australia, Sustainability Assessment Program, School of Civil and Environmental Engineering, Sydney, NSW 2052, Australia

Cropping Pattern Modifications Change Water Resource Demands in the Beijing Metropolitan Area

Abstract Adequate freshwater supply has become an issue of increasing local and international concern. Reducing water use in agriculture, which is the largest water using sector of the economy, is both important and urgent. The aim of this paper was to quantify how recent cropping pattern changes have influenced water resources in the great Beijing metropolitan area, an expanding megacity which also includes rural counties. Crop production affects blue water use through water consumption and water pollution, the latter assessed here using a critical dilution method. From 1990 to 2010, the total blue water used by crop production declined due to a decrease in overall cropped area, initially in response to local government policies favouring urban development. However, the average blue water use per hectare increased from 2 112 m 3 ha −1 yr −1 in 1990 to 2 764 m 3 ha −1 yr −1 in 2003, largely as the result of a transition from cereal to vegetable crops, and in particular an increase in intensively managed plastic and glass covered vegetable production systems. Current policies aim to conserve agricultural land, in the interests of food security, and to stimulate cereal production systems with higher ecosystem services provision. As such, in 2010 the average blue water use was 2 425 m 3 ha −1 yr −1 . These results demonstrate that cropping pattern changes in peri-urban regions and rural communities surrounding the Beijing metropolitan area can have a substantial impact on water resources. They also highlight the tradeoffs between food production and urban and industrial water supply and the need for integrated policy development.

Identification of methodological challenges remaining in the assessment of a water scarcity footprint: a review

PurposeThis work presents a systematic review, updating the information on the currently available methods to calculate the water footprint (WF), and addressing the following methodological challenges, as they have not been deeply studied to date: (1) accounting and assessing the environmental impacts related to changes in evapotranspiration (ET); (2) inventory of actual blue freshwater consumption in agriculture; (3) temporal and spatial variation to establish explicit characterisation factors (CFs) and (4) adequate connection between inventory flows and spatio-temporal explicit CFs.MethodsA systematic review relying on the guidelines of Pullin and Stewart (Conserv Biol 20(6):1647–1656, 2006) was conducted. Taking into account five specific formulated research questions in the WF field, WF studies were selected based on two ‘types’ of screening criteria: keyword searches and the WF study filter.Results and discussionFrom the 128 papers in peer-reviewed journals on product WF from a life cycle perspective, this literature review shows that major methodological challenges remain partially unsolved, which could degrade the accuracy of product WF assessments. To understand how land use affects ET, and depending on the land cover and size of the land use production system, actual ET can be estimated based on meteorological data on water balance equations embedded in crop and forest growth models, from field measurements at meteorological stations and more recently from remote sensing. For accounting for blue water consumption in agriculture, there are two types of approaches that lead to quite different results: inventory from actual farming records of applied irrigation and inventory from modelled ET associated with irrigation. Depending on the question being addressed, the practitioner can apply either approach. Furthermore, when a single freshwater scarcity CF is determined for large sub-watersheds, especially when the sub-watersheds have non-uniform freshwater availability and demand, uncertainty in the freshwater use-related impacts is introduced. Regarding the connection between inventory flows and spatio-temporal explicit CFs, the difficulty in identifying the exact location of background processes and characterising the local environmental characteristics (e.g. edaphoclimatic conditions, land cover) can hinder the elaboration of an accurate spatially differentiated impact assessment, as more generic CFs can be applied.ConclusionsThis systematic review shows that there are clearly future research needs with respect to the interrelations between freshwater use and potential damages in the areas of protection of resources, human health and ecosystem quality. It is also of paramount importance to understand the effects of land use and land cover change and water irrigation on WF damage.

Area of concern : a new paradigm in life cycle assessment for the development of footprint metrics

PurposeAs a class of environmental metrics, footprints have been poorly defined, have shared an unclear relationship to life cycle assessment (LCA), and the variety of approaches to quantification have sometimes resulted in confusing and contradictory messages in the marketplace. In response, a task force operating under the auspices of the UNEP/SETAC Life Cycle Initiative project on environmental life cycle impact assessment (LCIA) has been working to develop generic guidance for developers of footprint metrics. The purpose of this paper is to introduce a universal footprint definition and related terminology as well as to discuss modelling implications.MethodsThe task force has worked from the perspective that footprints should be based on LCA methodology, underpinned by the same data systems and models as used in LCA. However, there are important differences in purpose and orientation relative to LCA impact category indicators. Footprints have a primary orientation toward society and nontechnical stakeholders. They are also typically of narrow scope, having the purpose of reporting only in relation to specific topics. In comparison, LCA has a primary orientation toward stakeholders interested in comprehensive evaluation of overall environmental performance and trade-offs among impact categories. These differences create tension between footprints, the existing LCIA framework based on the area of protection paradigm and the core LCA standards ISO14040/44.Results and discussionIn parallel to area of protection, we introduce area of concern as the basis for a universal footprint definition. In the same way that LCA uses impact category indicators to assess impacts that follow a common cause-effect pathway toward areas of protection, footprint metrics address areas of concern. The critical difference is that areas of concern are defined by the interests of stakeholders in society rather than the LCA community. In addition, areas of concern are stand-alone and not necessarily part of a framework intended for comprehensive environmental performance assessment. The area of concern paradigm is needed to support the development of footprints in a way that fulfils their distinctly different purpose. It is also needed as a mechanism to extricate footprints from some of the provisions of ISO 14040/44 which are not considered relevant. Specific issues are identified in relation to double counting, aggregation and the selection of relevant indicators.ConclusionsThe universal footprint definition and related terminology introduced in this paper create a foundation that will support the development of footprint metrics in parallel with LCA.

Water Footprint of Cereals and Vegetables for the Beijing Market

Beijing is situated in water‐scarce northern China, where there is a history of policies aimed at constraining local agricultural water use to meet the increasing urban water demand. This has led to a change in local crop production and subsequent effects in terms of the importation of cereals and vegetables grown in other parts of China. The dilemma is that local policies designed to improve Beijings water resources situation may have the unintended consequence of increasing water stress in other regions. In this article, life cycle assessment approaches were used to model both consumptive and degradative water use for the major cereals and vegetables consumed in Beijing, enabling comparison of local and imported supplies. In the Beijing region, cropping cereals rather than intensive vegetables in greenhouses could reduce local blue water consumption by 7,216 cubic meters per hectare per year (m3 ha−1 yr−1) and nitrogen pollution by 45 kg ha−1 yr−1. However, depending on how the local food shortfall is balanced by imported food, shifts in cropping pattern in Beijing have the potential to cause either an improvement or exacerbation of the nationwide water stress situation (e.g., −42% to 4% for water scarcity footprint). As such, local policy making regarding agricultural land and water use needs to consider the wider food production context. This situation in Beijing is likely to be representative of the challenge facing many of the worlds large and mega‐sized cities, where a sustainable means of increasing food supply must be found.

Erratum to: Suspended solids in freshwater systems: characterisation model describing potential impacts on aquatic biota

Purpose High concentration of suspended solids (SS)—fine fraction of eroded soil particles—reaching lotic environments and remaining in suspension by turbulence can be a significant stressor affecting the biodiversity of these aquatic systems. However, a method to assess the potential effects caused by SS on freshwater species in the life cycle impact assessment (LCIA) phase still remains a gap. This study develops a method to derive endpoint characterisation factors, based on a fate and effect model, addressing the direct potential effects of SS in the potential loss of aquatic invertebrate or algae and macrophyte species.

Development and Application of a Water Footprint Metric for Agricultural Products and the Food Industry

The agriculture and food industries, which account for around 70% of global freshwater withdrawals and are an important source of chemical emissions to freshwater, are central to the issue of addressing global water stress. While water use efficiency is a longstanding and familiar concept, especially where water is a growth limiting factor for agricultural production, LCA-based water footprinting, which includes water use impact assessment, has recently emerged as an important parameter in LCM and the debate about sustainable food systems. This paper summarises recent case study evidence, noting that agriculture is not homogeneous and that it is dangerous to make generalisations about the water footprints of broad categories of food products and production regions. Issues of special significance to the water footprint of agriculture and food products, such as unmeasured flows, seasonal variations and rainwater flows, are discussed.