Uncovering the link between consumption and water use is helpful to formulate better water governance. The concept of water footprint was primarily formulated in the research context, to study the hidden water costs of human consumption. The concept helps to understand the relationships between production, consumption and trade patterns and water use and the global dimension in water governance.
Water footprint [WF] and carbon footprint [CF] concepts have many similarities; however, their roots and intended purposes differ. The CF was formulated to quantify the contribution of various activities to climate change. The history of the WF lies in the exploration of water use along supply chains and in the search for a tool to understand the global dimension of water as a natural resource. Although each footprint has different roots and characteristics and addresses different research and policy questions, there is a tendency to treat the WF in a similar way as the CF. For example, initiatives are taken to develop water labels for products in analogy to carbon labels and to incorporate the WF into Life Cycle Assessment (LCA) for products in the same way as was done with the CF. Each footprint needs to be seen within its appropriate context and interpreted with care as it is built around different research questions and tells a different story.
The carbon and water footprint concepts were introduced about a decade ago, simultaneously, but independently from one another. The CF arose out of the debate on climate change, as a tool to measure GHG emissions. The WF was introduced in the field of water resources management, as a tool to measure water use in relation to consumption patterns. In both cases, the terminology chosen was inspired by the ecological footprint [EF], which had been introduced in the 1990s.
All footprints measure,in different ways,human appropriation of the planet’s natural resources. The EF measures the use of bioproductive space in hectares; the WF measures the consumption and contamination of freshwater resources in cubic metres per year; and the CF measures the emission of gases that contribute to heating the planet in carbon dioxide equivalents [CO2e] per unit of time or product.
A common property of all footprints is that they can be related to specific activities, products and consumption patterns. Recently, the nitrogen footprint was introduced as a tool to measure the amount of nitrogen released into the environment in relation to consumption.
Unlike the CF, which emerged in practice, the WF was born in science. The WF started to gain broad interest from about 2008, the year in which the Water Footprint Network was established. The WaterFootprintNetwork is a network of academic institutions, governments, non-governmental organizations, companies, investors and UN institutions.
The carbon and water footprint concepts complement each other, addressing different environmental issues: climate change and freshwater scarcity.
Although there are similarities in the way both footprints are defined and calculated, they differ in important ways as well.
Both the CF and the WF are environment pressure indicators. Environmental pressure indicators measure the human use of natural resources and the anthropogenic emission of compounds into the environment, but they do not show the resulting change in the environment. The CF, for instance, shows GHG emissions, not the resultant higher GHG concentrations in the atmosphere or the subsequent changes in temperature, evaporation, precipitation or sea level. The WF shows the human consumption and contamination of freshwater resources, not the resultant changes in runoff and water quality in rivers and aquifers. As pressure indicators, the CF and WF show neither resultant environmental changes nor final impacts of those environmental changes on human beings (e.g. health) and ecosystems (e.g. biodiversity), but they are still useful measures of pressure that humans put on the environment for policy-makers working to address overexploitation of natural resources and the planet’s carrying capacity.
Ercin, A. E. and A. Y. Hoekstra (2012). Carbon and Water Footprints. Concepts, Methodologies and Policy Responses. United Nations World Water Assessment Programme, UNESCO. 4.