A water footprint shows how much water people use when they consume goods and services. It includes the total amount of fresh water needed to make the things people use. Water use is measured by how much water is used up (evaporated) or made dirty over time. A water footprint can be calculated for any group of people, such as an individual, family, or city, or for any business, product, or process like growing rice.
Traditionally, water use has been studied by looking at how much water is taken from three areas: farming, industry, and homes. While this gives useful information, it does not fully explain how water is used globally, since products are often made in one place and used in another. When agricultural or industrial products are traded internationally, they move water along with them, called virtual water or embodied water.
In 2002, the water footprint idea was created to better understand how water is used based on what people consume, not just where it is taken from. This is similar to the ecological footprint concept from the 1990s. A water footprint shows not only how much water is used and polluted but also where this happens. Managing water fairly and sustainably is important because of water shortages, climate change, and environmental problems. The water footprint helps guide better water use by showing how economic choices affect water availability and the environment worldwide.
Definition and measures
Water footprint has several parts, and each part has its own way of being described. Blue water footprint is the use of water from lakes, rivers, or underground sources. Green water footprint is the use of rainwater that is stored in the soil where plant roots are. Grey water footprint is the amount of water needed to clean up pollution so that the water becomes safe to use again.
Water footprint can be measured as the amount of water used, such as liters or cubic meters. Other ways to measure it include how much water is used for each unit of something made, like energy, food, or products. For example, it might be measured as liters of water used for each unit of energy produced, or liters used for each square kilometer of farmland, or liters used for each ton of goods made.
Blue water footprint is the amount of water taken from lakes, rivers, or underground sources. This water may be used for farming, industry, or homes. It can be lost through evaporation, used in products, or moved from one place to another.
Green water footprint is the rainwater stored in the soil. This water is either lost through plants and evaporation or used by plants to grow. It is especially important for crops, trees, and plants grown for food.
Grey water footprint is the amount of water needed to clean up pollution, such as waste from factories, runoff from farms, or untreated wastewater. This is done so that the water meets safe quality standards. The calculation for grey water footprint is based on the amount of pollution, the highest allowed pollution level, and the natural pollution level already in the water.
The water footprint of a process is the amount of water used over time. For a product, it is the total water used in all steps of making it, divided by the number of products made. For people, businesses, or areas, water footprint is the total water used over a certain time. For example:
– A person’s water footprint is the total water used in all the products they consume.
– A community or country’s water footprint is the total water used by all its people.
– A company’s water footprint is the total water used in making all its products.
– A region’s water footprint is the total water used in all activities there. The virtual change in water for an area is the difference between the water brought in and the water sent out. The total water footprint for a country’s use is the sum of the water used in that area and the virtual change in water.
History
The idea of a water footprint was first introduced in 2002 by Arjen Hoekstra, a professor of water management at the University of Twente in the Netherlands. He was also a co-founder and scientific director of the Water Footprint Network. While working at the UNESCO-IHE Institute for Water Education, he created the water footprint as a way to measure how much water is used and polluted to make goods and services throughout their entire production process. A water footprint is part of a group of environmental measurements that also include carbon footprint and land footprint. This concept is connected to the idea of virtual water trade, which was introduced in the early 1990s by Professor John Allan, a 2008 Stockholm Water Prize winner. Detailed guides on calculating water footprints include a 2004 UNESCO-IHE report, a 2008 book titled Globalization of Water, and a 2011 manual called The Water Footprint Assessment Manual: Setting the Global Standard. In 2008, the Water Footprint Network was created through collaboration between leading global institutions.
The Water Footprint Network is an international group (a non-profit organization based in the Netherlands) that helps governments, businesses, and communities share knowledge, tools, and ideas about water scarcity and pollution. The network includes about 100 partners from different areas, such as companies, investors, regulators, non-governmental organizations, and researchers. Its mission is to support efforts to manage water resources more sustainably.
In February 2011, the Water Footprint Network, along with environmental groups, companies, research institutions, and the United Nations, launched the Global Water Footprint Standard. In July 2014, the International Organization for Standardization released ISO 14046:2014, a guide for people in different fields, such as businesses, governments, and researchers, to assess water footprints. This standard is based on life-cycle assessment (LCA) principles and can be used to evaluate water use in products and companies.
Life-cycle assessment (LCA) is a step-by-step method to evaluate the environmental effects of a product, process, or service. "Life cycle" includes all stages of a product’s existence, from making it, using it, maintaining it, and disposing of it, as well as obtaining the raw materials needed to create it. This method helps measure the impact of freshwater use on human health, the quality of nature, and the availability of resources. It is especially important for water-intensive products, such as agricultural goods, which require LCA to understand their effects. The impact of water use also depends on where it happens, so regional assessments are necessary. In short, LCA helps identify how water use affects products, people, companies, and countries, which can lead to reducing water use.
The Water Positive initiative is a concept where an organization, community, or individual goes beyond saving water and actively works to manage and restore water resources. A development project is considered water positive if it uses less water than it provides. This includes using practices and technologies that reduce water use, improve water quality, and increase water availability. The goal is to have a positive effect on water ecosystems and ensure that more water is conserved and restored than is used or lost.
Water availability
Each year, about 4% of the rain that falls on land worldwide (about 117,000 km³ or 28,000 cubic miles) is used by rain-fed agriculture. Approximately half of all rainfall on land evaporates or is used by plants through transpiration in forests and other natural or almost natural areas. The remaining water becomes groundwater or flows over the land as runoff. This is sometimes called "total actual renewable freshwater resources." In 2012, this amount was estimated at 52,579 km³ (12,614 cubic miles) per year. This water can be used directly in rivers or streams or after being taken from groundwater or surface water sources. In 2007, about 3,918 km³ (940 cubic miles) of this water was used globally. Of this, 2,722 km³ (653 cubic miles), or 69%, was used by agriculture, and 734 km³ (176 cubic miles), or 19%, was used by other industries. Most water used in agriculture is for irrigation, which accounts for about 5.1% of total actual renewable freshwater resources. Over the past 100 years, the world's use of water has increased quickly.
By sector
The water footprint of a product is the total amount of freshwater used to make it, including all steps in the production process. It also includes where and when the water is used. The Water Footprint Network has a global database called WaterStat that tracks the water footprint of products. About 70% of the world’s water is used in agriculture.
The water footprint of different diets can vary a lot, often depending on how much meat is eaten. A table shows average water footprints for common agricultural products.
The water footprint of a business, called the corporate water footprint, is the total amount of freshwater used directly or indirectly to run the business. This includes water used in manufacturing, supporting activities, and the supply chain of the business.
The Carbon Trust suggests that businesses should not only measure water volume but also consider other impacts, such as water availability, water quality, health effects, and risks to a company’s operations. For example, they helped GlaxoSmithKline (GSK) analyze these factors to reduce its water use.
The Coca-Cola Company has over 1,000 factories in 200 countries. Making drinks uses a lot of water. Critics say its water use has been high. Coca-Cola now aims to reduce its water footprint by treating used water so it can be safely returned to the environment. It also seeks to use sustainable sources for ingredients like sugarcane, oranges, and maize. These steps can lower costs, protect the environment, and help communities.
Many technology companies also face challenges with their water use, especially as AI grows. AI requires large data centers, which use a lot of water for cooling and electricity generation.
Meta plans to be "water positive" by 2030, meaning it will replace all its water use with restoration projects. It also aims to offset 200% of its water use in high-stress areas and 100% in medium-stress areas. Apple wants to replenish all water it uses in high-stress regions by 2030 and claims to be 40% toward this goal as of 2024.
Some companies are finding ways to reduce water use in data centers. Google uses non-potable water in over 25% of its data centers and recycles wastewater. Its Finland data center uses seawater for cooling, which is heated and then cooled again before returning to the sea. Microsoft uses air instead of water for cooling and is testing underwater data centers that use sea temperatures for cooling.
AI development is growing quickly, and data centers are expected to use 3.5% of the world’s electricity by 2030. This has raised concerns, especially in areas with limited water. While exact numbers are hard to find, places like the Great Salt Lake Basin show the impact, as water levels drop each year despite hosting many data centers.
An individual’s water footprint includes water used at home and water used to produce goods and services they use. The average global water footprint is 1,385 cubic meters per person each year. Some countries have different water footprints, as shown in the table.
By region
The water footprint of a nation is the total amount of water used to make the goods and services that people in that country use. Studying the water footprints of countries shows how water use and pollution are connected worldwide. Some countries depend heavily on water from other countries to produce goods, and the way people in many countries use resources affects how much water is used or polluted in other parts of the world. As global trade grows, these international water connections are likely to become even more important. Most of the water used in international trade (76%) comes from crops and products made from crops. Trade in animal products and industrial goods each contributes about 12% to global water use. Four main factors influence a country’s water footprint: how much people consume (linked to a country’s income), what people consume (such as high or low meat use), local climate conditions, and farming methods that affect water efficiency.
Water use related to consumption can be studied from two sides: the production side and the consumption side. The water footprint of production measures how much water is used or polluted locally to create goods and services in a country. The water footprint of consumption looks at how much water is used or polluted in a country (including water used in other countries to make imported goods) for all goods and services people use. These water footprints can also be measured for smaller areas like cities, provinces, or river basins.
The absolute water footprint is the total water used by all people in the world. A country’s per capita water footprint (its total water use divided by the number of people) helps compare water use between countries.
From 1996 to 2005, the global water footprint was 9.087 billion cubic meters per year. Of this, 74% was green water (used in plants), 11% was blue water (from rivers and lakes), and 15% was grey water (polluted water). On average, each person used about 3.8 liters of water per day. Most of this water was used in agriculture (92%), followed by industry (4.4%) and home use (3.6%). The water used to make goods for export was 1.762 billion cubic meters per year.
In total, India has the largest water footprint, using 987 billion cubic meters per year. However, when considering population size, the United States has the highest per capita water footprint at 2,480 cubic meters per person per year. Other countries with high per capita footprints include Greece, Italy, and Spain. Countries like Malaysia and Thailand also have high water footprints. In contrast, China has a lower per capita water footprint, averaging 700 cubic meters per person per year.
A country’s internal water footprint is the water used from its own resources. Its external water footprint is the water used in other countries to make goods and services that are imported and used by its people. When calculating a country’s water footprint, it is important to consider how much water is used in other countries (virtual water) and how much is used locally. To calculate a country’s total water footprint, subtract the water used abroad and add the water used in other countries.
The external water footprint varies widely between countries. Some African nations, like Sudan and Mali, have very small external footprints because they import few goods. In contrast, European countries like Italy and Germany have external water footprints that make up 50–80% of their total water use. Agricultural products that contribute most to external water footprints include beef, soybeans, wheat, cocoa, rice, cotton, and corn.
The top 10 countries that export the most virtual water are the United States (314 billion cubic meters per year), China (143 billion), India (125 billion), Brazil (112 billion), Argentina (98 billion), Canada (91 billion), Australia (89 billion), Indonesia (72 billion), France (65 billion), and Germany (64 billion).
The top 10 countries that import the most virtual water are the United States (234 billion cubic meters per year), Japan (127 billion), Germany (125 billion), China (121 billion), Italy (101 billion), Mexico (92 billion), France (78 billion), the United Kingdom (77 billion), and the Netherlands (71 billion).
On average, each person in the European Union uses 4,815 liters of water per day. About 44% of this is used in power production, mainly to cool thermal or nuclear power plants. In 2011, the EU used 0.53 billion cubic meters of water for gas, 1.54 billion for coal, and 2.44 billion for nuclear energy. Wind energy saved 387 million cubic meters of water in 2012, saving €743 million in costs.
In southern India, the state of Tamil Nadu is a major agricultural producer that relies heavily on groundwater for irrigation. Between 2002 and 2012, satellite data showed that groundwater levels dropped by 1.4 meters per year, which is about 8% more than the rate at which groundwater is naturally replenished.
Environmental water use
Agriculture uses water to help protect important land areas, and some water from rainfall helps maintain forests and wild lands. However, governments also manage water directly for the environment. For example, in California, where droughts often cause water shortages, about 48% of water used for specific purposes in an average year is for the environment, which is more than the amount used for agriculture. This water supports ecosystems by keeping streams flowing, protecting homes for fish and plants near water, and maintaining wetlands.
Criticism
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."
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 water movement, climate, geology, land shape, population, and demographics should also be taken into account. Nevertheless, high water footprint calculations do suggest that environmental concern may be appropriate.
Many of the criticisms, including the above ones, compare the description of the water footprint of a water system to generated impacts, which is about its performance. Such a comparison between descriptive and performance factors and indicators is basically flawed.
In regards to grey water footprints, the current system has difficulties when it comes to accurately depicting the effect of pollution and dilution based contributions towards water footprints as opposed to usage. The effects of contamination are not considered to be different from that of scarcity, though the two have different effects on both human life and the environment.
It is possible for many different waste byproducts to have effects on an ecosystem, and common water footprints approaches that only test for a few of these byproducts do not capture the complete harm done to the environment. One form of unaccounted for environmental degradation can be found in marine ecosystem degradation. One of the most widely considered concerns in marine ecosystem degradation pertains to eutrophication, which is measured by the amount of nitrogen emitted by a body of water. However, it is also possible for industrial waste to have other contaminants in the water, such as other oils or compounds, that can not be measured in the same way that eutrophication can, and therefore will not be accounted for in degradation reports without proper testing methods of their own.
Waste byproducts also affect the quality of drinking water in a similar manner. In China, the byproducts of industrial waste result in heavy metals and salts being polluted into the public water supply. Though water footprints methods do account for the actual water polluted by the contaminants, it does not factor in the amount of water needed to dilute the contaminated water in order to get it to reasonable levels. A similar phenomenon can be seen in an analysis on California's water usage. Whereas the blue and green water components were able to be traced by researchers, the gray water component proved to be difficult to obtain data for by comparison. Therefore, due to a lack of consideration of all factors, water footprints fails to capture the entirety of the impact of industrial waste. If the effects of a process on the environment are unclear during the process of water footprints, it decreases the accuracy of the resulting report.
Water footprints also have difficulties when attempting to trace the total environmental impact on a global scale, as opposed to the effect in a singular area. With the globalization of the economy and how multiple processes are involved in the creation of a product, different procedures may have different impacts on the environment. However, these processes can not be measured using general metrics, as the procedures that one facility may use to complete that process, be through necessity or efficiency, may not necessarily be the same as another facility tasked with the same procedure. This introduces spatiality – that is, the location from which waste originates – as another axis of consideration in the problem of evaluating water footprints. These implications apply to water footprints, as the environmental effects and contribution to scarcity similarly can not be assessed through generalization.
The spatial effects can also be observed when looking at the concepts of direct and indirect water footprints. Direct water footprint can be defined as water that is used at a specific site to generate or maintain conditions necessary to create a given product. Indirect water footprint can be defined as water that is used to complete the intermediate steps required for many products, such as harvesting foods or fuel sources. While direct water footprint can be measured by taking reports from a specific facility to the amount of water that they use or dilute, indirect water footprints brings their own complications. Indirect water footprints tend to have high variability due to geographical factors. For instance, One proponent of indirect water foot printing is tracing the amount of water used to extract the raw petroleum needed to transport a commodity. Since the amount of fuel used depends on the distance a shipment needs to travel, it can vary greatly between countries, depending on how far resources need to be transported. The multifaceted nature of indirect water footprint sources makes it difficult to accurately assess all of the separate aspects contributing to a product, and even more so the total impact.
Though these criticisms bring merit, these problems are somewhat reduced when water footprint is not used as a lone indicator, but is instead interpreted in context. On the topic of grey water, adequate consideration of all possible consequences of industrial processes can do well to alleviate these issues. When a well-rounded measurement is taken of all of the pollutants that a form of waste can introduce to the environment, it greatly enhances the accuracy of the calculation. On the issue of spatial differences, the use of water availability as a factor assists in determining the proportion of water in a given area a certain water footprint applies to. When data relevant to the specific situation is gathered, both about water and process used and different spatial factors, it becomes more feasible to extrapolate calculations using the water footprint system.
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 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). Furthermore, looking at the definition of the footprint itself, and comparing ecological footprint, carbon footprint and water footprint, we realize that the three terms are indeed legitimate.
Sustainable water use
Sustainable water use means carefully studying all sources of clean water to understand how much is being used now and in the future. It also looks at how using water affects areas downstream and the environment, as well as how polluted water harms nature and the economy. Managing water use includes setting rules, like charging people for water, to help control how much is used. In some places, water has spiritual meaning, and its use must respect these beliefs. For example, the Maori people in New Zealand believe water is the source of all life and have deep spiritual connections to water and places near it. At the national and global levels, keeping water sustainable needs long-term planning to find clean water sources and understand how choices affect the environment and economy. Reusing and cleaning water again is also important for sustainability, as it helps protect rivers, lakes, and groundwater.
Water footprint accounting has improved a lot in recent years, but it still needs a final step called sustainability assessment. One new idea is using sustainable efficiency and fairness ("Sefficiency in Sequity"), which helps evaluate how water is used in a way that is both efficient and fair.
Sectoral distributions of withdrawn water use
Several countries track how different sectors use water taken from rivers, lakes, and underground sources. For example, in Canada, in 2005, 42 billion cubic meters of water were taken, of which about 38 billion cubic meters were freshwater. The use of this water was divided among sectors as follows: electricity production used 66.2%, manufacturing used 13.6%, homes used 9.0%, farming used 4.7%, businesses and schools used 2.7%, water systems used 2.3%, mining used 1.1%, and oil and gas extraction used 0.5%. The 38 billion cubic meters of freshwater used in that year can be compared to Canada’s total annual freshwater supply, which is estimated at 3,472 billion cubic meters. In the United States, the use of water by sectors is different. In the US, farming uses about 39% of freshwater, electricity production uses 38%, industry uses 4%, homes use 1%, and mining (including oil and gas) uses 1%.
Within farming, water use includes irrigation and caring for animals. In the US, irrigation (including water lost during transport) accounts for about 38% of all freshwater used. Water used to grow crops for animal feed and forage accounts for about 9%, and other water use for the livestock sector (such as drinking water and cleaning facilities) accounts for about 0.7%. Because farming uses a large amount of water, changes in how much and how efficiently water is used in this sector are important. In the US, from 1980 (when water use in farming was highest) to 2010, water use in farming decreased by 23%, while US farm production increased by 49% during the same time.
In the US, data about irrigation water use is collected every five years through the Farm and Ranch Irrigation Survey, which is part of the Census of Agriculture. This data shows large differences in irrigation use across different farming sectors. For example, about 14% of land used for growing corn for food and 11% of soybean land in the US is irrigated, compared to 66% of vegetable land, 79% of orchard land, and 97% of rice land.