water footprint

A water footprint

 shows the extent of water use in relation to consumption by people.

 The water footprint of an individual, community, or business is defined as the total volume of fresh water used to produce the goods and services consumed by the individual or community or produced by the business. Water use is measured in water volume consumed (evaporated) and/or polluted per unit of time. A water footprint can be calculated for any well-defined group of consumers (e.g., an individual, family, village, city, province, state, or nation) or producers (e.g., a public organization, private enterprise, or economic sector), for a single process (such as growing rice) or for any product or service.[2]

Infographic of water footprints around the world

Traditionally, water use has been approached from the production side, by quantifying the following three columns of water use: water withdrawals in the agricultural, industrial, and domestic sector. While this does provide valuable data, it is a limited way of looking at water use in a globalised world, in which products are not always consumed in their country of origin. International trade of agricultural and industrial products in effect creates a global flow of virtual water, or embodied water (akin to the concept of embodied energy).

In 2002, the water footprint concept was introduced in order to have a consumption-based indicator of water use, that could provide useful information in addition to the traditional production-sector-based indicators of water use. It is analogous to the ecological footprint concept introduced in the 1990s. The water footprint is a geographically explicit indicator, not only showing volumes of water use and pollution, but also the locations.

 Thus, it gives a grasp on how economic choices and processes influence the availability of adequate water resources and other ecological realities across the globe (and vice versa).

There are many different aspects to water footprint and therefore different definitions and measures to describe them. Blue water footprint refers to groundwater or surface water usage, green water footprint refers to rainwater, and grey water footprint refers to the amount of water needed to dilute pollutants.

Blue water footprint

A blue water footprint refers to the volume of water that has been sourced from surface or groundwater resources (lakes, rivers, wetlands and aquifers) and has either evaporated (for example while irrigating crops), or been incorporated into a product or taken from one body of water and returned to another, or returned at a different time. Irrigated agriculture, industry and domestic water use can each have a blue water footprint.

Green water footprint

A green water footprint refers to the amount of water from precipitation that, after having been stored in the root zone of the soil (green water), is either lost by evapotranspiration or incorporated by plants. It is particularly relevant for agricultural, horticultural and forestry products.

Grey water footprint

A grey water footprint refers to the volume of water that is required to dilute pollutants (industrial discharges, seepage from tailing ponds at mining operations, untreated municipal wastewater, or nonpoint source pollution such as agricultural runoff or urban runoff) to such an extent that the quality of the water meets agreed water quality standards It is calculated as:

{\displaystyle {\frac {L}{c_{\text{max}}-c_{\text{nat}}}}}

where L is the pollutant load (as mass flux), c_max the maximum allowable concentration and c_nat the natural concentration of the pollutant in the receiving water body (both expressed in mass/volume).[6]

Calculation for different actors

The water footprint of a process is expressed as volumetric flow rate of water. That of a product is the whole footprint (sum) of processes in its complete supply chain divided by the number of product units. For consumers, businesses and geographic area, water footprint is indicated as volume of water per time, in particular:

• That of a consumer is the sum of footprint of all consumed products.
• That of a community or a nation is the sum for all of its members resp. inhabitants.
• That of a business is the footprint of all produced goods.

That of a geographically delineated area is the footprint of all processes undertaken in this area. The virtual change in water of an area is the net import of virtual water V_{i, net}, defined as the difference of the gross import V_i of virtual water from its gross export V_e. The water footprint of national consumption WF_area,nat results from this as the sum of the water footprint of national area and its virtual change in water.

The concept of a water footprint was coined in 2002, by Arjen Hoekstra, Professor in water management at the University of Twente, Netherlands, and co-founder and scientific director of the Water Footprint Network, whilst working at the UNESCO-IHE Institute for Water Education, as a metric to measure the amount of water consumed and polluted to produce goods and services along their full supply chain.

 Water footprint is one of a family of ecological footprint indicators, which also includes carbon footprint and land footprint. The water footprint concept is further related to the idea of virtual water trade introduced in the early 1990s by Professor John Allan (2008 Stockholm Water Prize Laureate). The most elaborate publications on how to estimate water footprints are a 2004 report on the Water footprint of nations from UNESCO-IHE the 2008 book Globalization of Water, and the 2011 manual The water footprint assessment manual: Setting the global standard.

 Cooperation between global leading institutions in the field has led to the establishment of the Water Footprint Network in 2008.

Water Footprint Network (WFN)

The Water Footprint Network is an international learning community (a non-profit foundation under Dutch law) which serves as a platform for sharing knowledge, tools and innovations among governments, businesses and communities concerned about growing water scarcity and increasing water pollution levels, and their impacts on people and nature. The network consists of around 100 partners from all sectors – producers, investors, suppliers and regulators – as well as non-governmental organisations and academics. It describes its mission as follows:

To provide science-based, practical solutions and strategic insights that empower companies, governments, individuals and small-scale producers to transform the way we use and share fresh water within earth's limits.

International standard

In February 2011, the Water Footprint Network, in a global collaborative effort of environmental organizations, companies, research institutions and the UN, launched the Global Water Footprint Standard. In July 2014, the International Organization for Standardization issued ISO 14046:2014, Environmental management—Water footprint—Principles, requirements and guidelines, to provide practical guidance to practitioners from various backgrounds, such as large companies, public authorities, non-governmental organizations, academic and research groups as well as small and medium enterprises, for carrying out a water footprint assessment. The ISO standard is based on life-cycle assessment (LCA) principles and can be applied for different sorts of assessment of products and companies.

Life-cycle assessment of water use

Life-cycle assessment (LCA) is a systematic, phased approach to assessing the environmental aspects and potential impacts that are associated with a product, process or service. "Life cycle" refers to the major activities connected with the product's life-span, from its manufacture, use, and maintenance, to its final disposal, and also including the acquisition of raw material required to manufacture the product.

 Thus a method for assessing the environmental impacts of freshwater consumption was developed. It specifically looks at the damage to three areas of protection: human health, ecosystem quality, and resources. The consideration of water consumption is crucial where water-intensive products (for example agricultural goods) are concerned that need to therefore undergo a life-cycle assessment

 In addition, regional assessments are equally as necessary as the impact of water use depends on its location. In short, LCA is important as it identifies the impact of water use in certain products, consumers, companies, nations, etc. which can help reduce the amount of water used.

Globally, about 4 percent of precipitation falling on land each year (about 117,000 km³ (28,000 cu mi) is used by rain-fed agriculture and about half is subject to evaporation and transpiration in forests and other natural or quasi-natural landscapes.

 The remainder, which goes to groundwater replenishment and surface runoff, is sometimes called "total actual renewable freshwater resources". Its magnitude was in 2012 estimated at 52,579 km³ (12,614 cu mi)/year.

 It represents water that can be used either in-stream or after withdrawal from surface and groundwater sources. Of this remainder, about 3,918 km³ (940 cu mi) were withdrawn in 2007, of which 2,722 km³ (653 cu mi), or 69 percent, were used by agriculture, and 734 km³ (176 cu mi), or 19 percent, by other industry.

 Most agricultural use of withdrawn water is for irrigation, which uses about 5.1 percent of total actual renewable freshwater resources

 World water use has been growing rapidly in the last hundred years.

The water footprint of a product is the total volume of freshwater used to produce the product, summed over the various steps of the production chain. The water footprint of a product refers not only to the total volume of water used; it also refers to where and when the water is used

 The Water Footprint Network maintains a global database on the water footprint of products: WaterStat

 Nearly over 70% of the water supply worldwide is used in the agricultural sector.

The water footprints involved in various diets vary greatly, and much of the variation tends to be associated with levels of meat consumption

 The following table gives examples of estimated global average water footprints of popular agricultural products.

(For more product water footprints: see the Product Gallery of the Water Footprint Network)

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 water used for producing/manufacturing or for supporting activities and the indirect water use in the producer's supply chain.

The Carbon Trust argue that a more robust approach is for businesses to go beyond simple volumetric measurement to assess the full range of water impact from all sites. Its work with leading global pharmaceutical company GlaxoSmithKline (GSK) analysed four key categories: water availability, water quality, health impacts, and licence to operate (including reputational and regulatory risks) in order to enable GSK to quantitatively measure, and credibly reduce, its year-on-year water impact.

The Coca-Cola Company operates over a thousand manufacturing plants in about 200 countries. Making its drink uses a lot of water. Critics say its water footprint has been large. Coca-Cola has started to look at its water sustainability.

 It has now set out goals to reduce its water footprint such as treating the water it uses so it goes back into the environment in a clean state. Another goal is to find sustainable sources for the raw materials it uses in its drinks, such as sugarcane, oranges, and corn. By making its water footprint better, the company can reduce costs, improve the environment, and benefit the communities in which it operates.

The water footprint of an individual refers to the sum of their direct and indirect freshwater use. The direct water use is the water used at home, while the indirect water use relates to the total volume of freshwater that is used to produce the goods and services consumed.

The average global water footprint of an individual is 1,385 m³ per year. Residents of some example nations have water footprints as shown in the table:

Global view of national per capita water footprints