Water footprint

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The water footprint concept was introduced in 2002 by A.Y. Hoekstra from UNESCO-IHE as an alternative indicator of water use. The concept was refined and accounting methods were established with a series of publications from two lead authors A.K. Chapagain and A.Y. Hoekstra from the UNESCO-IHE Institute for Water Education, now at WWF-UK and University of Twente respectively. The most elaborate publications on how to estimate water footprints are a 2004-report on the 'Water footprint of nations' from UNESCO-IHE and the 2008-book Globalization of Water by A.Y. Hoekstra and A.K. Chapagain, published by Blackwell, 2008. Cooperation between global leading institutions in the field has led to the establishment of the Water Footprint Network in 2008 that aims to coordinate efforts to further develop and disseminate knowledge on water footprint concepts, methods and tools.

 Blue, green and grey water footprint

A water footprint consists of three components: the blue, green and grey water footprint. The blue water footprint is the volume of freshwater that evaporated from the global blue water resources (surface water and ground water) to produce the goods and services consumed by the individual or community. The green water footprint is the volume of water evaporated from the global green water resources (rainwater stored in the soil as soil moisture). The grey water footprint is the volume of polluted water that associates with the production of all goods and services for the individual or community. The latter can be estimated as the volume of water that is required to dilute pollutants to such an extent that the quality of the water remains at or above agreed water quality standards.

 Water footprint of individual consumers

The water footprint of an individual consumer refers to the sum of direct and indirect freshwater use by the consumer. The direct water use is the water used at home. The indirect water use relates to the total volume of freshwater that is used to produce the goods and services consumed by the consumer.
The global average Water Footprint is 1240 m³ water/person/year. The Chinese average is 700 m³ water/person/year one of the smallest in the world and the United States's 2480 m³ water/person/year is the largest in the world which is published in a concise form in a journal The Finnish average Water Footprint is 1730 m³ water/person/year. The water footprint of the UK is 1695 m³ water/person/year.

Water footprint of businesses

The water footprint of a business, the 'corporate water footprint', is defined as the total volume of freshwater that is used directly or indirectly to run and support a business. It is the total volume of water use to be associated with the use of the business outputs. The water footprint of a business consists of two components: the direct water use by the producer (for producing/manufacturing or for supporting activities) and the indirect water use (in the producer’s supply chain).

Water footprints of nations

The water footprint of a nation shows the water that is used to produce the goods and services consumed by the inhabitants of the nation. It includes two components: the internal and the external water footprint. The first component refers to the appropriation of domestic water resources; the latter to the appropriation of water resources in other countries. About 65% of Japan's total water footprint comes from outside the country; about 7% of the Chinese water footprint falls outside China.

 Water footprint calculation standard

Since 2009 there is a global calculation standard for the water footprint, maintained by the Water Footprint Network, an international network of governments, corporations, non-governmental organizations and UN bodies.

 Criticism of the water footprint concept

Due to the recent spread of the water footprint as an indicator of water use, application and interpretation of the results may sometimes be performed to promote industrial activities that lead to facile criticism of certain products without discussing the results in further detail. The 140 litres required for coffee production for one cup might be of no harm to water resources as its cultivation occurs mainly in humid areas. Nevertheless, the resulting figures suggest the sum of water quantities as an environmental concern, a concern that may not always be justified given a region's specific set of factors, such as hydrology, climate, geology, topography, and so forth.
Recently, the concept has been criticized for the term "footprint," which can confuse people familiar with the notion of a carbon footprint since the water footprint concept, as described above, includes sums of water quantities without necessarily evaluating related impacts. This is in contrast to the carbon footprint, where carbon emissions are not simply summarized but normalized by CO₂ emissions, which are globally identical, to account for the environmental harm. The difference is due to the somewhat more complex nature of water; while involved in the global hydrological cycle, it is expressed in conditions both local and regional through various forms like river basins, watersheds, on down to groundwater (as part of larger aquifer systems).