SAI Platform Australia water footprint pilot project: wheat, barley and oats grown in the Australian state of New South Wales

Transcription

1 SAI Platform Australia water footprint pilot project: wheat, barley and oats grown in the Australian state of New South Wales Summary report Brad Ridoutt and Perry Poulton November, 2009

2 Enquiries should be addressed to: Brad Ridoutt CSIRO Sustainable Ecosystems Private Bag 10, Clayton South, Victoria 3169, Australia Phone: brad.ridoutt@csiro.au Copyright and Disclaimer 2009 CSIRO To the extent permitted by law, all rights are reserved and no part of this publication covered by copyright may be reproduced or copied in any form or by any means except with the written permission of CSIRO. Important Disclaimer CSIRO advises that the information contained in this publication comprises general statements based on scientific research. The reader is advised and needs to be aware that such information may be incomplete or unable to be used in any specific situation. No reliance or actions must therefore be made on that information without seeking prior expert professional, scientific and technical advice. To the extent permitted by law, CSIRO (including its employees and consultants) excludes all liability to any person for any consequences, including but not limited to all losses, damages, costs, expenses and any other compensation, arising directly or indirectly from using this publication (in part or in whole) and any information or material contained in it.

3 Contents 1. EXECUTIVE SUMMARY BACKGROUND Objectives: METHODS Crop production and irrigation water use Calculating the virtual water content (VWC) Calculating the water footprint Blue water consumption Gray water requirement Impact of land use Water footprint calculation RESULTS AND DISCUSSION Virtual water content of wheat grown in NSW Case study: Water footprint of grain in the Northern SD Water footprint of wheat, barley and oats grown in NSW CONCLUSIONS Next steps...17 REFERENCES APPENDIX 1: Example of Water footprint calculation... 20

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5 1. EXECUTIVE SUMMARY The consumption of one kg of wheat, barley and oats grown in the Australian state of New South Wales (NSW) has an equivalent potential to contribute to water scarcity as the direct consumption of 86.5, 80.7 and 65.4 litres of water (Table 1). These Australian-equivalent water footprints were calculated using the method of Ridoutt and Pfister (2009), which takes into consideration the type of water used and the local water scarcity. The method enables a quantitative comparison between different products, production systems and supply chains in terms of their potential to contribute to water scarcity. These figures do not represent the absolute volume of water required to grow these commodities. Although being of great interest to farmers and agronomists, the absolute volume of water needed to grow agricultural commodities is not correlated with the potential to cause environmental harm and is therefore not a useful indicator of environmental sustainability. The water footprints of many kinds of food and beverage products are now being reported in the popular media. This reflects a growing awareness that water scarcity has become a critical global issue. It is also leading to a rapidly increasing demand for businesses to measure, report and reduce negative social and environmental impacts arising from water use in their operations and supply chains. The problem is that there are a variety of approaches to water footprinting and the term is currently being used to mean different things in different settings. For Australian food producers, it is important that standardised approaches to water footprinting emerge and that they are scientifically-based, allow meaningful comparison between alternative products, production systems and supply chains, and that they do not discriminate against Australian agricultural practices. In this study, the water footprints of wheat, barley and oats were calculated using data published by the Australian Bureau of Statistics (ABS) for the year 2005/06. Unlike previous water footprint studies, this project also included the water used to manufacture farm inputs (e.g. fuel, fertilizer) and to supply farm services (e.g. farm advisory services, accountancy services). For wheat, the water footprint ranged from 1.50 l kg -1 in the South Eastern Statistical Division (SD) to 230 l kg -1 in the Murrumbidgee SD. Across the state, irrigation accounted for the vast majority of the water footprint (96.4%), with emissions to freshwater and farm inputs making a minor contribution (2.2 and 1.5% respectively). However, in regions using only minor amounts of irrigation, the water used to produce farm inputs made the largest contribution to the water footprint. For barley, the water footprint ranged from 1.42 to 211 l kg -1 and for oats, the water footprint ranged from 2.87 to 210 l kg -1. This study has provided baseline data on the water footprints of wheat, barley and oats which can be used by food manufacturers to calculate the water footprints of food products made from these ingredients.

6 The study has also highlighted the importance of describing impacts rather than volumes. The vast majority of Australian grains are produced without the use of supplemental irrigation and therefore with little potential to contribute to water scarcity. As an illustration, for the Northern SD, the production of one kg of wheat had an equivalent potential to contribute to water scarcity as a half flush of a modern 3-star water efficient toilet. Finally, we note that water footprinting focuses on a single issue, namely water scarcity. In the same way, carbon footprinting also focuses on a single issue, in this case greenhouse gas emissions. Major strategic decisions should only be taken after considering all of the relevant impact categories as well as the broader triple bottom line concerns. While irrigated cropping systems have the potential to contribute to water scarcity in ways that dryland systems generally don t, irrigated systems offer other advantages such as a greater resource use efficiency of land for food production. Table 1: The water footprint of wheat, barley and oats grown in the Australian state of NSW in 2005/06, calculated using the method of Ridoutt and Pfister (2009) Australian equivalent litres per kg Wheat Barley Oats NSW average (l kg -1 ) Statistical Division > Northern > North Western > Central West > Murray > Murrumbidgee > South Eastern Components (%) > Irrigation > Gray water > Land use change > Farm inputs

7 2. BACKGROUND Freshwater has become a scarce and overexploited natural resource in many parts of the world, with serious consequences for global food security and the health of freshwater ecosystems. As such, there is now a growing awareness throughout society of the seriousness of global water scarcity (Circle of Blue and Globescan, 2009) and a recognition that the impacts of human production systems and consumption patterns on freshwater resources must reduce in intensity. One complicating factor is that for most individuals and for many businesses, their burden on freshwater systems is largely indirect. At the consumer level, indirect (or virtual) water use through the consumption of food and other goods and services is far greater than direct water use, perhaps by a factor of ten or more. The same is true for many businesses, where the majority of burden on freshwater systems occurs in their supply chains. Agriculture is, by far, the largest consumer of freshwater, accounting for around 70% of withdrawals. A further complicating factor is the interconnectedness of global business, meaning that the local consumption of products and services is now intervening in the hydrological cycle throughout the world and to an extent that is rarely understood or appreciated. Therefore, despite the acknowledged need to mitigate the impacts of production and consumption on freshwater systems, there is at present a lack of transparency, and this has led to much recent interest in the concept of water footprinting. Due to the large volumes involved, water use in the agri-food sector is of particular concern, and sustainability has been questioned. As such, the water footprints of many kinds of food and beverage products have begun to appear in the popular media. For example, the Melbourne Age reported data from studies in the Netherlands indicating that it takes 140 litres of freshwater to produce a cup of coffee (125 ml), 200 litres for a glass of milk (200 ml), and 2000 litres for a cotton t-shirt (Gordon, 2007). Similar data have also appeared in The Australian, The Sydney Morning Herald and other publications. The problem is that there are a variety of approaches to water footprinting and the term is currently being used to mean different things in different settings. Probably the worst situation is where a single water footprint number is reported based on the absolute volume of water used in production. Water footprint values of this kind provide no indication of the type of water used, the local water scarcity, and therefore the potential for negative social and environmental impacts. Naturally, there is a difference between the use of natural rainfall that occurs over agricultural lands (so-called green water) and irrigation water (so-called blue water). The local water scarcity where water is consumed is also an important factor. Water consumption in a region of water abundance does not have the same potential to cause harm as water consumption in locations of water scarcity. Ridoutt et al. (2009a), in their case studies of Dolmio pasta sauce and Peanut M&Ms, showed that volumetric water footprints are not necessarily correlated with the potential to cause harm and are therefore not a useful indicator of environmental sustainability.

8 Volumetric approaches to water footprinting have also led to various strange and potentially misleading statements about Australian agriculture. For example, it has been reported that it takes 50,000 to 100,000 litres of water to produce a kg of Australian beef (Warren, 2008) and that Australia is the world s largest net exporter of water (Chapagain and Hoekstra, 2004). Such statements have the potential to damage the reputation of Australian agriculture and that of downstream food products. Recently, a revised calculation method for product water footprinting was developed by CSIRO in collaboration with ETH Zurich (Swiss Federal Institute of Technology). This approach overcomes many of the weaknesses of water footprinting methods based on volumes alone and enables a quantitative comparison between different products, production systems and supply chains in terms of their potential to contribute to water scarcity. This methodology has previously been successfully applied to several case study products with Mars Australia (Ridoutt and Pfister, 2009). With this background, SAI Platform Australia undertook a water footprint case study with CSIRO involving wheat, barley and oats grown in the Australian state of New South Wales (NSW). 2.1 Objectives: 1. To test and demonstrate the usefulness of the revised water footprinting methodology of Ridoutt and Pfister (2009) by applying it to a selection of major Australian commodities of relevance to SAI Australia members, namely wheat, barley and oats. Such shared baseline data is of value to SAI Australia members seeking to calculate the water footprint of their specific products, i.e. by combining the baseline data on the agricultural commodities with company specific data to cover downstream parts of the product life cycle. 2. Provide water footprinting case study evidence that can contribute to the wider international effort to develop a global water footprint standard. 3. Provide CSIRO with baseline data to address issues relating to the water footprint and environmental sustainability of Australian grain production. Recent discussion in the scientific and popular media about Australia being the world s largest exporter of water has raised issues about the sustainability of Australian agriculture. This project will enable CSIRO to inform this debate through an assessment of the impacts of consumptive water use in Australian grain production. The vast majority of Australian grains are produced without the use of supplemental irrigation and therefore with little potential to contribute to freshwater scarcity. 8

9 3. METHODS 3.1 Crop production and irrigation water use In Australia, farm survey data collected by the Australian Bureau of Statistics (ABS) are published at a range of levels, from the national to the state, statistical division and statistical local area. This water footprint pilot project is based on the most recent farm production and water use statistics published at the level of the statistical local area, i.e. the 7125 and 4618 data series covering the year 2005/06, released in 2008 (ABS 2008a, 2008b). For NSW, the focus of the analysis was the six major grain producing regions, which in the 2005/06 year accounted for more than 99% of the state s wheat, barley and oats production (Table 2; Fig 1). Areas of the state where grain production was trivial were not included in the analysis because of uncertainties and gaps in the data published by ABS. Table 2: Wheat, barley and oats production in NSW in 2005/06 (Source: ABS 7125) Wheat ( 000 t) Barley ( 000 t) Oats ( 000 t) Northern SD * 1, North Western SD 1, Central West SD 1, Murray SD 1, Murrumbidgee SD 1, South Eastern SD NSW Total 8,049 2, * SD = Statistical Division Whereas the ABS 7125 data series describes the production of specific crops, the ABS 4618 data series reports water use for the broad category of cereal crops for grain or seed (excluding rice). Therefore, the ABS data does not describe the area of wheat, barley and oats grown under irrigation nor does it describe the volume of irrigation water applied to these specific crops. In NSW, maize is the cereal crop (excluding rice) which is most commonly irrigated. Therefore, for each statistical local area where maize was grown, irrigation water use was estimated using the APSIM modelling platform (Keating et al. 2003; Table 3). The balance of the water use reported by ABS was then distributed to wheat, barley, oats, triticale and sorghum, assuming an increased likelihood that wheat was irrigated compared to barley and oats, and also that barley and oats were more likely to be irrigated than triticale and sorghum. In addition, it was assumed that when wheat was irrigated, the rate of application was 1.5 times that of other cereals. On this basis, the area of irrigated wheat, barley and oats production was estimated as well as the irrigation volume applied. This approach gave priority to the ABS farm water use statistics and was deemed to be sufficiently accurate for the purposes of this study considering that the overall

10 use of irrigation for grains production in NSW is small (3.7% of the cropping area in 2005/06) and that it would be a complex and expensive task to produce a more rigorous estimate. Figure 1 New South Wales, Statistical Divisions (Source: ABS, 2006) Table 3: Estimated volume of irrigation water applied to cereals for grain or seed in NSW in 2005/06 ( 000 ML). Total Maize Wheat Barley Oats Triticale Sorghum Northern SD * North Western SD Central West SD Murray SD <0.1 Murrumbidgee SD <0.1 South Eastern SD * SD = Statistical Division Source: ABS and CSIRO modelling 10

11 3.2 Calculating the virtual water content (VWC) In order to make a comparison with existing literature, the virtual water content (VWC, l kg -1 ) of wheat grown in NSW was calculated using the following equation: Crop yields were obtained from the ABS statistics described in Section 3.1. Crop water use (the sum of evaporation and transpiration) was estimated using APSIM modelling of irrigated and dryland wheat crops to produce yields consistent with the ABS data at the level of the statistical local area and using meteorological data for the 2005/06 season. The production weighted average for the state was subsequently calculated. 3.3 Calculating the water footprint The water footprints of wheat, barley and oats were calculated using the method of Ridoutt and Pfister (2009; Fig 2), which takes into consideration the type of water used and the local water scarcity via the water stress index (WSI) of Pfister et al. (2009). In contrast to the water footprinting method advocated by the Water Footprint Network ( the method of Ridoutt and Pfister (2009) enables a quantitative comparison between different products, production systems and supply chains in terms of their potential to contribute to water scarcity. This method is most relevant to water footprinting studies which are product-oriented and involve assessments of products that are produced in multiple locations. The method is not designed to address local issues pertaining to the sustainable management of specific watersheds. Figure 2 Revised method of calculating product water footprints incorporating water stress characterisation factors.

12 3.3.1 Blue water consumption Blue water, appropriated from surface and groundwater sources, enters into the cereal cropping process in two ways. Firstly, there is the direct use of blue water associated with irrigation, which is described in Section 3.1. Secondly, there is the blue water used to manufacture farm inputs (e.g. fuel, fertilizer) and to supply farm services (e.g. farm advisory services, accountancy services). The latter was calculated using ABARE data on expenditure by NSW farmers engaged in wheat and other cropping for the 2005/06 year ( as well as environmental input-output data (Foran et al., 2005) and other data describing water use per dollar of final demand for various categories of goods and services in the Australian economy. Where necessary, CPI multipliers were used to adjust financial data to the year 2005/ Gray water requirement Gray (or dilution) water is the volume of freshwater needed to assimilate emissions to freshwater (Chapagain et al., 2006). The rationale is to include in the water footprint calculation a measure of the impact on water resource availability of emissions to freshwater from a product system. The gray water calculation method is admittedly imperfect as a litre of water extracted directly from a resource is not physically or conceptually the same as a litre of water assimilating an emission. Nevertheless, it is considered beneficial to include the gray water calculation rather than lose from the water footprint any consideration of the impacts of water quality degradation on usable water quantity. Nitrate leaching from the cropping system (kg ha -1 ) was estimated using APSIM modelling at the level of the statistical local area. The gray water requirement was calculated based on the US EPA s recommended limit for nitrate in drinking water of 10 mg l -1 (measured as nitrogen) Impact of land use Land use has the potential to change the availability of blue water by altering the stream flow and runoff. Of particular concern in the Australian context is the transformation of pasture into industrial forestry with deep rooted tree species which, in certain circumstances, may increase evapotranspiration and reduce stream flow (Benyon et al., 2007). However, most annual cropping systems intercept less precipitation than the natural ecosystems they replace (Scanlon et al., 2007). Indeed, simulations using the LPJmL dynamic global vegetation and water balance model suggest that globally, river discharges have increased by 6.6% as a result of transformation of natural ecosystems to crop and grazing land (Rost et al., 2008). Therefore, the wheat, barley and oats cropping systems of NSW were assumed to have no negative impact on the availability of water resources as a result of land occupation. Apart from considerations of the impact of land use on drainage and stream flow, the revised water footprint calculation method of Ridoutt and Pfister (2009) does not specifically include green water consumption. This is because the consumption of green water by agriculture does not contribute to water scarcity in any regional or global context. Until it becomes blue water, green water does not contribute to environmental flows which are needed for the health of freshwater ecosystems, nor is it accessible for other human uses. Green water is only accessible 12

13 through access to and occupation of land. Indeed, green water is only one of the many resources acquired through land occupation: access to solar radiation, wind and soil are others. Therefore, due to the inseparability of green water and land, the consumption of green water should not be included in water footprint calculations Water footprint calculation Application of the revised water footprint calculation method of Ridoutt and Pfister (2009) involved, as an intermediate step, the calculation of the volumetric impact on blue water resources, which is the summation of blue water consumption, gray (or dilution) water requirement and the impact of land use on blue water resources (Fig. 2). For each statistical local area, the volumetric impact on blue water resources, expressed on a production basis (e.g. l kg -1 ), was multiplied by the local water stress characterisation factor derived from the water stress index (WSI) of Pfister et al. (2009). The average Australian WSI was used in relation to farm inputs where the exact location of production was unknown. Australian-equivalent water footprints were subsequently calculated by dividing the stress-weighted water footprints by the Australian average WSI (0.402). Australian-equivalent water footprints describe the volume of direct water use having an equivalent potential to contribute to water scarcity. The production weighted average for each statistical division and for the state was subsequently calculated. 4. RESULTS AND DISCUSSION 4.1 Virtual water content of wheat grown in NSW Much of the water footprint data that has been promulgated in the popular media in Australia has been taken from the UNESCO-IHE report: Water Footprints of Nations (Chapagain and Hoekstra, 2004). This information is freely accessible through the www site of the Water Footprint Network (waterfootprint.org). According to Chapagain and Hoekstra (2004), the global average virtual water content of wheat is 1334 l kg -1. This same report claims that the virtual water content of Australian wheat is 1588 l kg -1, suggesting that compared to the global average, Australia is a water inefficient producer of wheat. The underlying tenet of Chapagain and Hoekstra s research is that agricultural commodities should be sourced from countries where they can be grown most water efficiently. On the basis of Chapagain and Hoekstra s calculations, Australia would appear to be a less preferred source of wheat. The problems with Chapagain and Hoekstra s analysis are many. However, two will be specifically addressed below. Firstly, Chapagain and Hoekstra (2004) base their analysis on country average climatic data. For a large and climatically diverse country like Australia, the national average is unlikely to

14 accurately represent local growing conditions. As such, we have concerns about the reliability of much of the data published in their report and on the Water Footprint Network www site. When the virtual water content was calculated for wheat grown in NSW, using APSIM modelling to produce yields consistent with the ABS data for the 2005/06 season and using local metrological records for this period, the production weighted average was 1234 l kg -1. In contrast to Chapagain and Hoekstra (2004), our findings, based on local data, suggest above average water productivity for wheat grown in this large Australian state. Secondly, we would argue that the virtual water content of a crop is not a useful sustainability indicator because it does not take into consideration the type of water being used and the local water scarcity (Ridoutt et al. 2009a). While it is encouraging that there is now an increased level of corporate and public awareness about global water scarcity and the links to the production and consumption of food products, information about the virtual water content of products is unlikely to inform wise decision making by businesses or by individuals that will lead to a more sustainable use of the world s freshwater resources. The situation can be compared to the concept of food miles, which has led to increased awareness of the link between greenhouse gas (GHG) emissions and the production and consumption of goods and services, but is now generally understood to be a poor sustainability indicator. For many products, the GHG emissions associated with transportation are a fraction of the total emissions over the full product life cycle. As such, purchasing decisions based on food miles alone are unlikely to lead to substantial GHG reductions and, in certain instances, could lead to perverse outcomes. In the same way, the relationship between the virtual water content of a product and the potential to cause environmental or social harm is unclear. Therefore, we recommend against the use of the virtual water content as a product-level sustainability indicator. We also recommend against the use of water footprint calculation methods, such as those used by the Water Footprint Network, which are numerically equivalent to the virtual water content. 4.2 Case study: Water footprint of grain in the Northern SD The Northern Statistical Division (SD) of NSW includes the Moree Plains and Narrabri to the west, Gunnedah and Liverpool Plains to the south and Armidale and Glen Innes Severn to the east. The region is a substantial producer of grain (2,763,850 t in 2005/06), using predominantly dryland production systems. In 2005/06, only 1.8% of the cropping area was irrigated (all cereals). The Australian equivalent water footprints of wheat, barley and oats grown in this region were respectively 3.14, 2.19 and 3.69 l kg -1 (Table 4). 14

15 What this means is that the consumption of one kg of wheat, barley or oats grown in the Northern SD, has an equivalent potential to contribute to water scarcity as a half flush of a modern 3-star water efficient toilet requiring 3 litres of direct water use. This is not to say that the water used to flush a toilet is necessarily a direct substitute for the water used to produce grain in the Northern SD. However, both activities, the consumption of one kg of grain grown in the Northern SD and the direct consumption of 3 litres of water, apply a similar level of burden on freshwater resources in the respective locations where the water use occurred. Whereas the total volume of water required to grow one kg of grain in the Northern SD may exceed 1000 litres, the impact of that water consumption is more realistically compared to 3 litres of direct water use. For grain production in the Northern SD, the majority of the water footprint related to the use of irrigation water and the water associated with farm inputs (Table 4). Water footprint studies of agricultural commodities have generally not considered the water it takes to manufacture farm inputs (e.g. fuel, fertilizer) and to supply farm services (e.g. farm advisory services, accountancy services). These results for the Northern SD demonstrate that for agricultural production systems that are predominantly dryland, farm inputs can represent a major proportion of the overall water footprint. This is an important consideration for the ISO work programme that is developing an international water footprinting standard. Table 4: The Australian-equivalent water footprints (WF) of wheat, barley and oats produced in the Northern SD of New South Wales in 2005/06 (l kg -1 ). Wheat Barley Oats Australian equivalent WF (l kg -1 ) Components (%) > Irrigation > Gray water > Land use change > Farm inputs WFN-Australian average* (l kg -1 ) 1,588 1,425 1,533 * Chapagain and Hoekstra (2004) 4.3 Water footprint of wheat, barley and oats grown in NSW The Australian-equivalent water footprints of wheat, barley and oats grown in NSW were respectively 86.5, 80.7 and 65.4 l kg -1 (Table 5).

16 There was substantial variation between Statistical Divisions, largely explained by the varying use of supplemental irrigation. For the 2005/06 season, 8.8 and 10.7% of the cropping area (all cereals, excluding rice) was irrigated in the Murray and Murrumbidgee Statistical Divisions. However, less than 2% of the cropping area was irrigated in the Northern, North Western, Central West and South Eastern Statistical Divisions. These water footprint results can be compared with other products which have been assessed by CSIRO (Ridoutt and Pfister 2009, Ridoutt et al. 2009b), including: Dolmio pasta sauce (575 g jar): 350 l Peanut M&Ms (250 g bag): 31 l Australian grown fresh mango: 101 l kg -1 Table 5: The Australian-equivalent water footprints (WF) of wheat, barley and oats produced in NSW in 2005/06 (l kg -1 ). Wheat Barley Oats NSW average (l kg -1 ) Statistical Division > Northern > North Western > Central West > Murray > Murrumbidgee > South Eastern Components (%) > Irrigation > Gray water > Land use change > Farm inputs CONCLUSIONS The term water footprint is currently being used to mean different things in different settings. It is important that, where the expression is used in relation to the sustainability of products, a consistent, international standard emerges. This will avoid creating misunderstanding and confusion among the public. It will also encourage uptake by companies and this is what will 16

17 ultimately lead to genuine improvements in agricultural sustainability, more sustainable use of the world s freshwater resources and more resilient agri-food businesses. Not all consumptive water use has the same potential to cause negative social and environmental impacts. Therefore, approaches to water footprinting that report the absolute volume of water required grow agricultural commodities or to manufacture a product are not a useful sustainability indicator. In this study, the water footprinting calculation method of Ridoutt and Pfister (2009) was used. This method enables a quantitative comparison between different products, production systems and supply chains in terms of their potential to contribute to water scarcity. The method has enabled dryland and irrigated production systems to be differentiated in terms of their potential to contribute to water scarcity. It is essential that water footprinting calculation methods are able to make this distinction because irrigated cropping systems have the potential to contribute to water scarcity in ways that dryland systems generally don t. However, that said, we do not arbitrarily discriminate against irrigated agriculture. Water footprinting focuses on a single issue, namely water scarcity, in the same way that carbon footprinting also focuses on a single issue, in this case greenhouse gas emissions. Major strategic decisions should only be taken after considering all of the relevant impact categories as well as the broader triple bottom line concerns. While irrigated cropping systems may have an increased potential to contribute to water scarcity, they offer other advantages such as a greater resource use efficiency of land for food production. This project has also demonstrated that the water footprinting methodology of Ridoutt and Pfister (2009) produces assessments which are suitable for public dissemination, by permitting the water used to produce a product to be realistically compared to an equivalent volume of direct water use. 5.1 Next steps This study has provided baseline data on the water footprints of wheat, barley and oats which can be used by food manufacturers to calculate the water footprints of food products made from these ingredients, i.e. by combining the baseline data on wheat, barley and oats with company specific data to cover the downstream parts of the product life cycle. The water footprint case study evidence obtained in this project will also contribute to the wider international effort to develop a global water footprint standard. CSIRO is in the process of engaging with Standards Australia who is representing Australia in the ISO work programme around water footprinting. CSIRO is also planning to prepare an article for publication in an international science journal. This article will inform the international debate about sustainable food systems in the context of global water scarcity and food security concerns.

18 REFERENCES ABS [Australian Bureau of Statistics]. 2008a Water Use on Australian Farms, 2005/06, Estimates for Australian Standard Geographical Classification (ASGC) Regions. Commonwealth of Australia. ABS [Australian Bureau of Statistics]. 2008b Agricultural Commodities: Small Area Data, Australia 2005/06. Commonwealth of Australia. ABS [Australian Bureau of Statistics] Australian Standard Geographical Classifications (ASGC). Commonwealth of Australia. Benyon, R., England, J., Eastham, J., Polglase, P. and White, D Tree water use in forestry compared to other dry-land agricultural crops in the Victorian context: Report prepared for the Department of Primary Industries Victoria. Ensis Technical Report No Chapagain, A.K. and Hoekstra, A.Y Water footprints of nations. Value of Water Research Report Series No.16, UNESCO-IHE, Delft, the Netherlands. Chapagain, A.K., Hoekstra, A.Y., Savenije, H.H.G. and Gautam, R The water footprint of cotton consumption: An assessment of the impact of worldwide consumption of cotton products on the water resources in the cotton producing countries. Ecological Economics 60: Circle of Blue and Globescan. (2009). Water Issues Research. df Foran, B., Lenzen, M. and Dey, C Balancing act: A triple bottom line analysis of the Australian economy. CSIRO and University of Sydney. Gordon, J Australian households world s worst at water use. The Age (Monday May 21), p.3. Keating, B.A., Carberry, P.S., Hammer, G.L., Probert, M.E., Robertson, M.J., Holzworth, D., Huth, N.I., Hargreaves, J.N.G., Meinke, H., Hochman, Z., McLean, G., Verburg, K., Snow, V., Dimes, J.P., Silburn, M., Wang, E., Brown, S., Bristow, K.L., Asseng, S., Chapman, S., McCown, R.L., Freebairn, D.M. and Smith, C.J An overview of APSIM, a model designed for farming systems simulation. European Journal of Agronomy 18: Pfister, S., Koehler, A. and Hellweg, S Assessing the environmental impacts of freshwater consumption in LCA. Environmental Science & Technology 43: Ridoutt, B.G. and Pfister, S A revised approach to water footprinting to make transparent the impacts of consumption and production on global freshwater scarcity. Global Environmental Change Human and Policy Dimensions (in press), doi: /j.gloenvcha

19 Ridoutt, B.G., Eady, S.J., Sellahewa, J., Simons, L. and Bektash, R. 2009a. Water footprinting at the product brand level: Case study and future challenges. Journal of Cleaner Production 17: Ridoutt, B.G., Juliano, P., Sanguansri, P. and Sellahewa, J. 2009b. Consumptive water use associated with food waste: Case study of fresh mango in Australia. Hydrology and Earth System Sciences Discussions 6: Rost, S., Gerten, D. and Heyder, U Human alterations of the terrestrial water cycle through land management. Advances in Geosciences 18: Scanlon, B.R., Jolly, I., Sophocleous, M. and Zhang, L Global impacts of conversions from natural to agricultural ecosystems on water resources: Quantity versus quality. Water Resources Research 43(3): WO3437. Warren, M Slim pickings. The Australian (Thursday October 2), p.13.

20 APPENDIX 1: EXAMPLE OF WATER FOOTPRINT CALCULATION Production statistics for wheat grown in Narrabri SLA in 2005/06 Area: 107,686 ha (A) Area (dryland): 100, ha (B) Area (irrigation): 7, ha (C) Production: 256,452 t (D) Irrigation applied: 13,187 ML (E) Nitrate loss (dryland): kg ha -1 (F) Nitrate loss (irrigation): kg ha -1 (G) Nitrate loss (average): kg ha -1 (H) Relevant WSI values: Narrabri: m 3 m -3 (I) Australian average: m 3 m -3 (J) Water footprint calculation for wheat grown in Narrabri SLA in 2005/06 Blue water consumption by irrigation: = E = 13,187 ML (K) Blue water consumption (farm inputs): = 3094 l ha -1 x Area (A) = 333 ML (L) Gray water requirement: > Emission to freshwater of N = H x A = 59,581 kg of Nitrate (M) > = M x 14/62 x 1,000,000 mg of N (N) > Limit = 10 mg l -1 of N (O) > Gray water requirement = (N/O)/1,000,000 = 1,345 ML (P) Impact of land use on blue water resources: 0 ML (Q) Stress-weighted water footprint = (K x I) + (L x J) + (P x I) + (Q x I) = 493 ML (R) = (R x 1,000,000)/(D x 1,000) = 1.92 l kg -1 (S) Australian-equivalent water footprint = S/J = 4.78 l kg -1 (T) 20

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