Water use

Water use can mean the amount of water used by a household or a country, or the amount used for a given task or for the production of a given quantity of some product or crop, or the amount allocated for a particular purpose.

Globally, of precipitation falling on land each year (about 117,000 cu.km), about 4 percent is used by rainfed 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 recently estimated at 52,579 cu.km/year. It represents water that can be used either instream or after withdrawal from surface and groundwater sources. Of this remainder, about 3,918 cu.km were withdrawn in 2007, of which 2,722 cu.km (69 percent)  were used by agriculture, and 734 cu.km (19 percent) by other industry. Most agricultural use of withdrawn water is for irrigation, which uses about 5.1 percent of total actual renewable freshwater resources.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 (see graph from New Scientist article ).

There are numerous measures of water use, including total water use, water consumption, non-consumptive use, withdrawn water use (from surface and groundwater sources), instream use, water footprint, etc. Each of these (and other) measures of water use is appropriate for some purposes and inappropriate for others. Water “footprints” have become popular measures of use, e.g. in relation to personal consumption. The term "water footprint" is often used to refer to the amount of water used by an individual, community, business, or nation, or the amount of water use associated with (although not necessarily assignable to) a product.

The total water footprint of a typical 3-person household in the U.S. is 23,360 liters (6171 gallons). By comparison, a typical single family home in the U.S. only uses about 262 liters (69.3 gallons) of per day (2008 estimate). This includes (in decreasing order) toilet use, washing machine use, showers, baths, faucet use, and leaks.

Water footprint
The water footprint of an individual, community or business is defined as the total volume of freshwater 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). The water footprint is a geographically explicit indicator, not only showing volumes of water use and pollution, but also the locations.

The water footprint of a country is related to what its people eat. In 1993, Professor John Allan (2008 Stockholm Water Prize Laureate), strikingly demonstrated this by introducing the "virtual water" concept, which measures how water is embedded in the production and trade of food and other products. For example, it is a common thought that the water involved in a cup of coffee is just the water in the cup. There is actually 140 litres of involved. The 140 litres of is the amount of water that was used to grow, produce, package, and ship the coffee beans. A hamburger needs an estimated 2,400 litres of. This hidden water is technically called virtual water. Therefore, eating a lot of meat means a large water footprint. However, care is needed to avoid misunderstanding the significance of water footprints of food. (See "Water footprint of products", below.)

Water footprint is one of a family of footprint indicators, which also includes carbon footprint and land footprint.

History
The water footprint concept was introduced in 2002 by Arjen 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, later moved to WWF-UK and University of Twente in the Netherlands 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, 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 that aims to coordinate efforts to further develop and disseminate knowledge on water footprint concepts, methods and tools.

Water Footprint Network (WFN)
The Water Footprint Network is an international learning community (non-profit foundation under Dutch law) that serves as a platform for connecting communities interested in sustainability, equitability and efficiency of water use. The organization has two work programmes: a Technical Work Programme and a Policy Work Programme. In addition, there is a Partner Forum which offer partners of the WFN a way of receiving, contributing and exchanging knowledge and experience on water footprint. Its mission and activities are listed below and taken directly from the Water Footprint website.

blue 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 (either lost through evapotranspiration, incorporated in products or transferred to non-blue catchments).

green water footprint
The green water footprint is the volume of water evaporated from the global green water resources (rainwater stored in the soil as soil moisture) during production or those incorporated in products.

grey water footprint
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. It is calculated as $$WF_{proc, grey}=\frac{L}{c_{max}-c_{nat}}$$ where L is the pollutant load (as mass flux), cmax the maximum allowable concentration and cnat the natural concentration of the pollutant in the receiving water body (both expressed in mass/volume).

sustainable water use
Being sustainable means using blue water wisely and not making grey water. Humans have polluted much water. Some rivers have so much rubbish in place that boats are pushing their way through the rubbish, for example, the Lake Karachay in Russia. It was the dumping site for radioactive waste, the water under the rubbish has chemicals from factories and toilets.

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 water balance of an area is the net import of virtual water Vi, net, defined as the difference of the gross import Vi of virtual water from its gross export Ve. The water footprint of national consumption WFarea,nat results from this as the sum of the water footprint of national area and its virtual water balance.

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. On July 24, 2014, ISO issued ISO 14046:2014, Environmental management—Water footprint—Principles, requirements and guidelines. The ISO standard is based on the Global Water Footprint Standard, which can be applied for different sorts of Water Footprint Assessment: for products, companies, countries or river basins.

Life Cycle Analysis of water use
Life Cycle Analysis (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 in the course of the product’s life-span from its manufacture, use, and maintenance, to its final disposal, including the raw material acquisition 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 and 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.

Water footprint of products
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 (Source: WFN Glossary). The Water Footprint Network maintains a global database on the water footprint of products: WaterStat

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 some examples of estimated global average water footprints of some agricultural products.

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

Interpretation of an agricultural product’s water footprint is complex for various reasons, including the fact that much of it can be associated water use that is not actually assignable to that product. The beef water footprint provides an example illustrating some considerations involved in understanding the significance and applicability of such footprints.

It has been estimated that globally, 94 percent of the water footprint of beef is “green water”, i.e. soil water supplied directly by precipitation and used in evapotranspiration. (The transpiration is carried out by vegetation providing feed for the cattle. ) On rangeland, as much as 99.5 percent of water use associated with beef production is green water, and this green water use by evapotranspiration would occur even in the absence of cattle. Thus, despite the large water footprint of beef, production of beef on rangeland results in an extremely small increase in total water use there, while greatly increasing the amount of food produced per unit amount of water used. This is an especially important consideration wherever livestock can be raised on agricultural land unsuitable for crop production, because green water use there cannot feasibly be reallocated to alternative kinds of agricultural production.. Such land is extensive. In the US, for example, about 51 percent of non-federal pasture and rangeland is unsuitable for cultivated crop production, and an additional 39 percent has severe or very severe limitations for cultivated crop production.

Most of the beef water footprint represents water used in production of the vegetation that provides feed. However, in addition to providing the plant parts consumed by cattle, that water use produces plant biomass (roots, stubble, etc.) important for erosion control, stabilization of soil structure, nutrient cycling, carbon sequestration, support of numerous primary consumers, etc.. On temperate pasture, for example, much more than half of the plant biomass produced in a season can be below ground. and for various reasons, above-ground biomass utilization by livestock may be limited to some extent. Thus much more than half of the water use represented by a beef water footprint is likely to be producing environmental values, not beef, and must still be used even when beef is not being produced, if those terrestrial environmental values are to be maintained.

The beef water footprint is calculated by partitioning water use associated with beef cattle production. This partitioning is done not among all products of beef cattle, but only among a few co-products, ignoring other co-products and by-products. Partitioning among the major co-products is not done simply on a product mass basis, but is adjusted by applying product value factors. Thus, for example, where a beef water footprint is nominally expressed in litres per kilogram of beef, it actually refers to litres per value-adjusted kilogram of beef.

Even a food with a small water footprint (expressed as litres per kilogram) may pose very serious water conservation concerns if produced in large amounts under irrigation in an area where its irrigation requirements compromise sustainability, or where competing demands for withdrawable water are deemed to have higher socioeconomic priority. Conversely, production of a food with a much larger water footprint may be quite benign in the same area, if produced less intensively, or if most of the footprint is green water.

The above considerations are among reasons why water footprints are usually inappropriate measures of water use for analysis of water allocation, sustainability of water use, environmental impact, etc., involving agricultural products. Where agricultural product water footprints are invoked, great care is needed to ensure that their implications are not misinterpreted.

Water footprint of individual consumers
The water footprint of an individual refers to the sum of his or her 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 in some example nations have a water footprints as shown in the table:

Water footprint of companies
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.

Water footprint of nations
The water footprint of a nation is the water used to produce the goods and services consumed by the inhabitants of the nation. The internal water footprint is the appropriation of domestic water resources; the external water footprint is 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.

Europe
Each EU citizen consumes 4,815 litres of water per day on average, 44% is used in power production primarily to cool thermal plants or nuclear power plants. Energy production annual water consumption in the EU 27 in 2011 was as billion m3 for gas 0.53, coal 1.54 and nuclear 2.44. Wind energy avoided the use of 387 million cubic metres (mn m³) of water in 2012 avoiding a cost of €743 mn. The cost of droughts in Europe over the past thirty years is according to the European Commission €100 billion.

Insufficient consideration of consequences of proposed water saving policies to farm households
According to Dennis Wichelns of the International Water Management Institute: ''Although one goal of virtual water analysis is to describe opportunities for improving water security, there is almost no mention of the potential impacts of the prescriptions arising from that analysis on farm households in industrialized or developing countries. It is essential to consider more carefully the inherent flaws in the virtual water and water footprint perspectives, particularly when seeking guidance regarding policy decisions.''

Insufficient consideration of regional water scarcity
The application and interpretation of water footprints may sometimes be used to promote industrial activities that lead to facile criticism of certain products. For example, the 140 litres required for coffee production for one cup might be of no harm to water resources if its cultivation occurs mainly in humid areas, but could be damaging in more arid regions. Other factors such as hydrology, climate, geology, topography, population and demographics should also be taken into account. Nevertheless, high water footprint calculations do suggest that environmental concern may be appropriate.

The use of the term "footprint" can also confuse people familiar with the notion of a carbon footprint, because the water footprint concept 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 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).

The water footprint of a business, the 'corporate water footprint', is defined as the total volume of fresh water 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. Water Credit for conserving water: Nagpur based innovator Shripad Vaidya's idea of giving water credit's, much like carbon credits, to those who save and conserve water is gaining ground. These water credits can be marketed or sold to those in need of surplus water for social,agricultural or industrial ventures.

Environmental water use
Although agriculture’s water use includes provision of important terrestrial environmental values (as discussed in the “Water footprint of products” section above), and much “green water’ is used in maintaining forests and wild lands, there is also direct environmental use (e.g. of surface water) that may be allocated by governments. For example, in California, where water use issues are sometimes severe because of drought, about 48 percent of “dedicated water use” in an average water year is for the environment (somewhat more than for agriculture). Such environmental water use is for keeping streams flowing, maintaining aquatic and riparian habitats, keeping wetlands wet, etc.

Sectoral distributions of withdrawn water use
Several nations estimate sectoral distribution of use of water withdrawn from surface and groundwater sources. For example, in Canada, in 2005, 42 billion cu. m of withdrawn water were used, of  which about 38 billion cu. m was freshwater. Distribution of this use among sectors was: thermoelectric power generation   66.2%, manufacturing  13.6%, residential  9.0%, agriculture 4.7%, commercial and institutional 2.7%, water treatment and distribution systems   2.3%, mining  1.1%, and oil and gas extraction 0.5%. The 38 billion cu.m of freshwater withdrawn in that year can be compared with the nation’s annual freshwater yield (estimated as streamflow) of 3,472 billion cu.m.  Sectoral distribution is different in many respects in the US, where agriculture accounts for about 39% of fresh water withdrawals, thermoelectric power generation 38%, industrial 4%, residential 1%, and mining (including oil and gas) 1%.

Within the agricultural sector, withdrawn water use is for irrigation and for livestock. Whereas all irrigation in the US (including loss in conveyance of irrigation water) is estimated to account for about 38 percent of US withdrawn freshwater use, the irrigation water used for production of livestock feed and forage has been estimated to account for about 9 percent, and other withdrawn freshwater use for the livestock sector (for drinking, washdown of facilities, etc.) is estimated at about 0.7 percent. Because agriculture is a major user of withdrawn water, changes in the magnitude and efficiency of its water use are important. In the US, from 1980 (when agriculture’s withdrawn water use peaked) to 2010, there was a 23 percent reduction in agriculture’s use of withdrawn water, while US agricultural output increased by 49 percent over that period.

In the US, irrigation water application data are collected in the quintennial Farm and Ranch Irrigation Survey, conducted as part of the Census of Agriculture. Such data indicate great differences in irrigation water use within various agricultural sectors. For example, about 14 percent of corn-for-grain land and 11 percent of soybean land in the US are irrigated, compared with 66 percent of vegetable land, 79 percent of orchard land and 97 percent of rice land.