SummaryThe water footprint is the sum of the water used directly or indirectly to produce goods and services consumed by humanity. Agricultural production accounts for most of global water use, but drinking, manufacturing, cooking, recreation, washing, cleaning, landscaping, cooling, and processing all contribute to water use. General Information about this IndicatorWhat is it?: The water footprint is the sum of the water used directly or indirectly to produce goods and services consumed by humanity. Agricultural production accounts for most of global water use, but drinking, manufacturing, cooking, recreation, washing, cleaning, landscaping, cooling, and processing all contribute to water use (Hoekstra et al. 2011). In addition to these direct water uses, indirect uses such as water impacted by pollutants, chemical or temperature, contribute to the water footprint. The water footprint is a composite of water use indicators (“blue water”, “green water” and “gray water”) and is used here as an index of water sustainability. Blue water is the water that is retrieved from a natural source and managed (e.g., through a reservoir or pipes) before it used to make a good or service. Green water is naturally-occurring precipitation that plants use to grow (e.g., crop plants). Gray water is the water impacted by the discharge from production and is the sum of the water required to reduce pollutants to acceptable levels. The Water Footprint Network developed a global water footprint standard that contains definitions and calculation methods for determining water footprints for different purposes and scales (Hoekstra et al., 2011). The assessment contains four steps: Setting goals and scope, water footprint accounting, water footprint sustainability assessment, and water footprint response formulation. There are different types of water footprints: the water footprint of a product, consumer, community, national consumption, business, and any geographic area. The level of detail needed for data as well as the frequency of measurements depends on the spatial scale assessed. Why is it important?: By measuring and understanding the many ways that Californians use water, whether it is through pipes or from food production, we can reduce the risks and uncertainty associated with certain ways of using water in production and improve our water sustainability. As global climate change occurs, different parts of the world will be affected differently, which will affect the reliability of receiving imported goods and services. This will in turn affect water management in California as domestic sources either make up for shortfalls in imports through increased production, or reduce their water use due to international trade pressures. Calculating and using the water footprint in water planning and assessment is an acknowledgement that we participate both in global trade and in one water cycle. WF and Food Production Coupling virtual water with economic information describing the production value of a crop can further strengthen agricultural water management. 'Water economic productivity', expressed in terms of crop market value per cubic meter of water used, has been derived, for example, for the Guadiana River Basin, Spain (Aldaya et al., 2010). That study distinguished 'low virtual water, high economic value' crops from 'high virtual water, and low economic value' alternatives, in a semi-arid region characterized by irrigated agriculture. The findings showed that 'high virtual water, low economic value' crops such as cereals are widespread in the region, in part due to the legacy of earlier subsidies. The study concludes that the agricultural sector will need to modify its water use greatly if it is to achieve significant water savings and environmental sustainability. WF and Supply Chain Vulnerability Water Footprint assessment has been recognized by various corporation as important in understanding the vulnerability of their supply chains to the changing availability of water to make products that feed into their supply chain. Because most water footprint assessments have not addressed the environmental impacts of water use, corporate organizations are increasingly moving away from water foot-printing alone towards water stewardship approaches. The UK retailer, Marks & Spencer, uses a three-tiered approach, drawing on the water footprint methodology: Tier 1: standards Marks & Spencer defines criteria that their suppliers have to meet. Tier 2: risk Marks & Spencer tries to use information on water risk in its supply chains to identify which products are from areas at risk of water stress. This has included using both Water Footprint Assessment and other tools. Tier 3: influence using the information on water risk in their supply-chain, Marks & Spencer identifies which suppliers to target with its water stewardship approach. Marks & Spencer is not simply targeting suppliers located in areas at risk of water stress — after all, a supplier may be working sustainably even if located in a high risk area. Sustainable suppliers are given an award for sustainable practice. Marks & Spencer is also working with WWF and the Food Ethics Council to foster stakeholder engagement. WF Based on Income Water Footprint is a useful meme to characterize both our dependence on water and our impacts on water systems. Consumption of goods and services requires delivery of water through natural and engineered pathways and return of wastewater to the environment. The greater the consumption, the greater the water footprint. Because there is variation in income in California and the US, as there is elsewhere in the world, it is useful to estimate water footprint using income classes as one way to control for this variation. The Water Footprint Network has developed an online calculator that estimates the water footprint based on income (http://www.waterfootprint.org/?page=cal/waterfootprintcalculator_indv; Mekonnen, 2009). A higher water footprint is both a greater impact on world water systems and a sign of vulnerability. Maintenance of a high water footprint may not be sustainable in a water-constrained world. Meat-based diet and higher income classes in the study area both had greater water footprints than the county averages and global averages. These lifestyles may become less sustainable with increased water limitations, or, if maintained, put unsustainable strain on water limited systems. What can Influence or Stress Condition?: The water footprint of each person is based on summing the amount of “virtual water” embedded in the goods and services consumed (Hoekstra, 2012). Diet, income, consumption patterns, energy use, and other personal preferences and activities all affect individual water footprint. Thus, individual lifestyle choices are the most influential on water footprint. In a geographic area, like a state, the water footprint of consumption depends on the aggregate of individual consumption and of production depends on the water use to make goods and services that are used within the area, or exported. The water footprint of the area does not include exported goods. The water use for goods and services produced within or outside (and imported into) an area defines the water footprint of the area. Thus, the water use decisions of producers and trade/import decisions of product providers will be most influential on water footprint. Water availability and competition among users of limited water sources are the most influential on the source and type of water used to make goods and services and whether or not the goods and services will be available for export. Climate change and population growth are thought to be very influential factors in water stress and competition in the future, which will influence the size and composition (product variety) of future peoples’ water footprint. Target or Desired Condition: The water footprint has been calculated for most countries, including the US, and recently for California. The average footprint for someone in California is ~1,500 gal/day (Fulton et al., 2012). This is slightly less than the water footprint of the average US resident of ~1,600 gal/day (Mekonnen and Hoekstra 2011) and greater than the global average of ~750 gal/day. The scoring approach used states that the best score (100) is for water footprints that are less than the global average and sets a score of 0 at the largest global water footprint (Bolivia, 3,500 gal/day).Additional Details: Aldaya, M.M., M.R. Llamas. 2009. Water footprint analysis (hydrologic and economic) of the Guadania River Basin. Report of the United Nations World Water Assessment Programme. Pp. 39. Fulton, J., H. Cooley, and P.H. Gleick. 2012. California’s Water Footprint. Report of the Pacific Institute. Pp. 53. Hoekstra, A., Chapagain, A., Aldaya, M., and Mekonnen, M., 2011. The Water Footprint Assessment Manual: Setting the Global Standard, London: Earthscan. Hoekstra, A.Y. and Mekonnen, M.M. 2012. The water footprint of humanity. Proceedings of the National Academy of Sciences 109(9): 3232-3237. Mekonnen, M.M. 2012. Web-based individual water footprint calculator. MSc Thesis, UNESCO-IHE Institute for Water Education, Delft, the Netherlands. Pp. 64. Wu, Y. (2004) Understanding International Food Consumption Patterns, School of Economics and Commerce, University of Western Australia. http://www.ecom.uwa.edu.au/__data/page/49786/04_05_Wu_part_2.pdf Indicator Preparation InformationData Sources: Fulton et al., 2012 Census 2011, American community Survey 2011 estimates of income by county (http://factfinder2.census.gov/faces/tableservices/jsf/pages/productview....) Water Footprint Network, Quick Water Footprint Calculator (http://www.waterfootprint.org/?page=cal/waterfootprintcalculator_indv) Data Transformations: WF Based on Income The Census Bureau conducts surveys of community characteristics between the decadal population census, including household income. The Water Footprint Network includes a calculator of water footprint (Mekonnen, 2012) for different countries, based on diet, gender, and income. In this study, the water footprint was calculated using the WFN Quick Calculator for men and women eating vegetarian and meat-based diets. The distribution of water footprint for residents in different California counties was compared to the distribution of income within those counties. In addition, the effect of variation in diet was examined for the same distribution of incomes. The income tables for specific California counties were downloaded from the “Fact Finder” tool on the Census Bureau website. These tables included proportion of population in each major household-income category (e.g., $50,000 to $74,999 per year), as well as basic statistics about household composition and total number of households. The median value in each income category was calculated and used to estimate water footprint. The Quick Water Footprint Calculator was used to calculate water footprint based on gender, diet, and income. Three diet choices were provided: vegetarian, average meat consumption, and high-end meat consumption. For most calculations, “average meat consumption” was chosen to represent the most people. Because most households have two adults of opposite gender, the average of male and female water footprint was used and household income was assumed to represent two adults for the purposes of the water footprint calculation.