Over the lifecycle of a product or activity, the amount of water consumed, withdrawn or used is called the ‘water footprint’ (but it can also include the water polluted and contaminated over a product lifecycle, as degraded water can’t be used unless treated)
In this guide, we explain important information relating to water footprints, along with virtual water.
Summary – Water Footprints, & Virtual Water
A water footprint is the volume of water consumed, evaporated and polluted/contaminated, direct and indirect water that is used for a product or service over it’s complete lifecycle (or, over a specific part of the life cycle, such as production)
For example, when you eat rice or a piece of fruit, water is required to grow that food, as well as deliver it to a food store.
When you drive a car, there is water used in the manufacturing, as well as to wash the car. There is even water used to refine the gasoline that a car runs on, or at the mechanics when you take the car to get serviced or repaired.
Evaporated, and polluted and contaminated water is also included in a water footprint because these types of water are often non recoverable
There’s different ways a water footprint can be expressed in terms of unit of measurement
For example, with food, it could be expressed as water required per 1 kg, per calorie, per gram of protein, per serving, and so on. It could also be expressed for an individual, a corporate entity, a city or a whole country. It could be expressed for a single process, or for a whole lifecycle
The different types of water in a water footprint are the blue (from surface water and ground water sources), green (from rainfall – such as rainfed crops) and grey water footprints (water required to dilute waste water, or polluted/contaminated water)
Even importing products from other countries carries a water footprint, although it should be noted it’s often the country doing the exporting that have their water supplies being depleted or impacted (importing countries can save water this way)
Global water trade can open up efficiencies in allocating water to those regions and countries who most need it, from those who have a surplus
There are limitations to using a water footprint or measuring virtual water i.e. just relying on water volume stats to make a decision about whether a product is sustainable or not. Volume based water footprint stats don’t take into account local context and conditions – for example, a high water footprint is not bad if the product comes from an area where fresh water is abundant, or where water or certain products or services are vital in providing local jobs and a livelihood for people. Another example is that just because water is saved in one activity, it doesn’t mean that that same saved water can practically be used for another activity – there’s practical and economic considerations for doing so.
A single water footprint number is simply one of many factors to do with water use that someone might look at
*Note – measuring and expressing a water footprint can’t be 100% accurate because of how complex and difficult data gathering can be, and data given to researchers is often incomplete as well. A water footprint is more of an indicator we can use to pick up trends and patterns of specific products, items and activities, and to make general comparisons.
What Is A Water Footprint?
A general description of a water footprint might be:
A water footprint is the volume of total direct and indirect water consumed, evaporated and polluted/contaminated during a specified stage of a product’s lifecycle, or the whole lifecycle (from the material sourcing stage, all the way through to disposal)
A water footprint reveals water use patterns – specifically of the non recoverable water used in a process or lifecycle
It can be calculated for a single product stage, or a whole lifecycle
It can be calculated for an individual, or who households, companies, cities, States and countries
A water footprint can be expressed in many ways – per weight of production, per dollar of production, per gram of protein produced, per calorie produced, and more
Water footprints give people and organisations a reference of how much total water, or how much of a specific water type of water (blue, green, grey) a product uses
This can give us a better idea of how to sustainably manage our fresh water resources
The watercalculator.org and waterfootprint.org resources in the list below have further definitions of what a water footprint is.
Different Types Of Water Footprints – Blue, Green & Grey
The different types of water in a water footprint might be:
- Blue (surface water and ground water),
- green (rainfall)
- and grey water (water required to dilute waste water) footprints are all different.
These water footprints can be looked at separately, or added together for a total water footprint.
They offer another layer of specificity and delineation for us to be able to manage our water supplies sustainably.
Green water might be most preferable, but blue water can sustainably be used in areas with consistent rainfall and larger natural supplies of freshwater.
- Blue Water Footprint: The amount of surface water and groundwater required (evaporated or used directly) to produce an item.
- Green Water Footprint: The amount of rainwater required (evaporated or used directly) to make an item.
- Grey Water Footprint: The amount of freshwater required to dilute the wastewater generated in manufacturing, in order to maintain water quality, as determined by state and local standards.
- Blue water footprint – is water that has been sourced from surface or groundwater resources and is either evaporated, 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 – is water from precipitation/rainfall that is stored in the root zone of the soil and evaporated, transpired or incorporated by plants. It is particularly relevant for agricultural, horticultural and forestry products.
- Grey water footprint – is the amount of fresh water required to assimilate pollutants to meet specific water quality standards. The grey water footprint considers point-source pollution discharged to a freshwater resource directly through a pipe or indirectly through runoff or leaching from the soil, impervious surfaces, or other diffuse sources
- Green Water Footprint (Rainfall) – Precipitation/rainfall. Is stored temporarily as surface or soil moisture and used directly on crops
- Grey Water Footprint (pollution arising from production of a good or service) – Water required to treated polluted run off and production water to acceptable levels
- Blue Water Footprint (Irrigation) – Water stored in rivers, lakes or aquifers, and used during irrigation and production
- The overwhelming majority of water in the water footprint of some common foods/crops is green water, followed by blue, followed by grey
- Conventionally, consumption of green water — essentially free to use in most cases, and much of which would be consumed by noncrop plants anyhow — is preferable over blue water, which depletes aquifers and impacts ecosystems if overused.
- Most provinces in China consume predominantly green water for agricultural production, but that volumes of green and blue water required to raise given crops or livestock vary widely across the country
- [Earth Magazine also further discusses how China, Mongolia etc. use blue, green and grey water in their article]
You can see examples of how Green, Blue and Grey water is used separately for certain products here:
- Water Footprint Of Different Products (waterfootprint.org)
- Virtual Water Tracking (earthmagazine.org)
What Is ‘Virtual Water’ Or ‘Hidden Water’?
Virtual water or hidden water is the water you don’t see that goes into the process of making something.
For example, with a cotton shirt, not only is water used to grow cotton, but it can also be used in the manufacturing stage, like during wet processing for example with bleaching, printing, and dyeing.
Another example is the separate materials used to make a car – steel, rubber, plastic, leather, foam etc. Not only is water used in the manufacturing process for cleaning, cooling and so on when the car is being put together, but it is used for these raw materials that make up the car (and even in the process of extracting or making those materials).
- … [virtual water] is water that is not felt or seen but is used for the production processes for many different raw materials and finished products.
- … smartphones in particular have virtual water associated with their manufacturing (grey water footprint) …
- Phones are composed of many pieces created in multiple steps, and each step consumes water. Numerous resources, materials and parts go into smartphone manufacturing …
- … in the case of the smart phone, [grey water which is the water used to clean and dilute the wastewater] makes up the largest portion of its total water footprint.
- When the water required for all the steps to make a smart phone is added up, the water footprint of the production of a single phone is an estimated 3,190 gallons.
- Closely linked to the water footprint concept is the virtual water concept.
- Virtual water is defined as the volume of water required to produce a commodity or service.
- Virtual water trade (also known as trade in embedded or embodied water) refers to the hidden flow of water if food or other commodities are traded from one place to another.
- … the virtual-water content of a product (a commodity, good or service) is “the volume of freshwater used to produce the product, measured at the place where the product was actually produced”. It refers to the sum of the water use in the various steps of the production chain.
- The water is said to be virtual because once … wheat is grown [for example], the real water used to grow it is no longer actually contained in the wheat.
- The concept of virtual water helps us realize how much water is needed to produce different goods and services.
Direct & Indirect Water Use
Direct water is the water used directly by an individual or company, whilst indirect water is the water that was used at a previous stage i.e. earlier in the supply or manufacture chain/process.
One example is with a manufacturer who might use water directly in their factory as part of their manufacturing process, or for cleaning. But, they may use water indirectly if the materials they bought from supplier have used water in the extraction or making of those materials.
Another example is at the household level:
- Direct water – water used for drinking, bathing, cleaning, gardening and lawns etc.
- Indirect water – households also eat food and use electricity. Water is used at the farm level for irrigation, and at the power plant level for electricity generation. The household level does not see this war usage, even though they get the end product – food, or electricity
- … the direct water footprint … is the water used directly by the individual(s) and the indirect water footprint … [is] the summation of the water footprints of all the products consumed.
There’s also this explanation for manufacturing:
- Direct water usage – bringing water into a manufacturing facility for an industrial process
- Indirect water usage – when a manufacturing facility is buying items from the supply chain that were manufactured by someone else using water, then incorporating those materials into the finished product
The industries that use the most direct water are:
- In terms of direct water usage, nobody beats the agriculture and power-generation industries, which together are responsible for 90 percent of direct water withdrawals.
- Yet a majority of water usage (about 60 percent) is indirect.
- About 96 percent of industry sectors use more water indirectly than directly in their supply chains.
Limitations Of The Water Footprint Concept, & Virtual Water, & Putting It Into Context
The consensus seems to be that whilst a water footprint or virtual water statistics can provide some perspective on water use, it can’t be used a sole indicator of water use.
They may be best used in an integrated approach with other water usage stats, tools and information, whilst also weighing up other relevant factors.
How water footprints can be used:
- Virtual water volumes, for example, are used to calculate water footprints — estimates of direct and indirect water use by producers and consumers — which have been used as an outreach tool to raise awareness of sustainability concerns.
- And both virtual water analyses and water footprints have been cited by many as potentially valuable tools for influencing trade and water policies to promote conservation and combat water scarcity [but they aren’t a magic bullet]
- … virtual water is a useful, albeit limited tool for addressing water issues …
- … calculations of virtual water are inconsistent or inaccurate
- … volumetric indicators ignore important local socioeconomic factors related to water consumption
- … and … if used to guide trade or water allocation policies, they could end up hurting the very populations at risk from water scarcity.
- Some countries like Spain and India have used the concept for help in forming regulations and policies
- [Other countries like Australia and the Netherlands have taken the opposite approach – saying virtual water has little practical value for governmental decision making]
- … virtual water and water footprints can be good [for public awareness]
- [One problem with] purely volumetric measures [is that they] lack vital context … especially the local socioeconomic and environmental conditions where … food or clothes are produced [prior to being exported, often to developed countries]
- You have to know: Where does the product come from? Is there water scarcity there? Are there human rights injustices there? Is there pollution there during the growing of the crops? …
- A high water footprint is not a bad thing … [when it comes from a] water-abundant region or from a region with sound water management in place does no harm
- [Sri Lanka is an example of a place where rain is abundant, and people depend on water for employment and their livelihoods]
- Virtual water and water footprints should ideally be embedded in a broader narrative around water management, productive water use, domestic and international trade
- A sustainability index or indicator should capture all the important elements of a problem you are trying to solve. Virtual water and water footprints, which don’t capture all of the necessary elements, have been misused as sustainability indices.
- Water footprints consider only the volume of water used in production, without considering other inputs or opportunity costs.
- Water volumes, alone, are not sufficient indicators of the benefits or costs of water use in any setting.
- The benefits and costs are functions of complex interactions involving physical, economic, and social dimensions that are not contained or reflected in estimates of water footprints.
- Comparing two water footprints across activities, locations, or time is not a helpful exercise if one does not have information regarding water scarcity conditions, the opportunity costs of water, and water’s role in supporting livelihoods in each setting.
According to Wikipedia:
Key shortcomings of virtual water measures are that the concept:
- [Not all water types or sources are of] equal value.
- [Just because less water is used in one activity, it doesn’t mean that saved water can be used in another activity, and additionally, the alternate use for the water might not be economically friendly]
- It fails as an indicator of environmental harm nor does it provide any indication of whether water resources are being used within sustainable extraction limits. The use of virtual water estimates therefore offer no guidance for policy makers seeking to ensure that environmental objectives are being met.
For specific parts of the world, such as the MENA (Middle East & North Africa) region, there would also be specific short comings in using virtual water measures.
See also these resources for more reasons that the virtual water footprint concept can be limited:
- Some Reservations About Virtual Water (globalwaterforum.org)
- Water Footprint Can Be One Dimensional In Some Ways (globalwaterforum.org)
How A Water Footprint Might Be Used More Effectively
According to earthmagazine.org:
- [Water problems need to be solved on the local level – not globally]
- Water footprints need to target individual countries, states, river basins or even cities [for accuracy and relevance]
- Patterns of water use are really driven not by countries, they’re driven by cities
- Virtual water should have to do with what you are using the water for, what value you are creating, in terms of jobs and money, what you are getting for your water use, and how we are dependent on our neighbors at a very small scale. It should also distinguish among green, blue and gray water (because they are not all equal from a financial, cultural and environmental perspective)
- How best to measure gray water and how comparable it is to green and blue water is one reporting area that can be refined. Polluted water/grey water may need to be separated out from the virtual water reporting
- How far upstream through supply and production chains one accounts for in calculations, for instance, will clearly affect the results of virtual water reporting, as will the quality of data available in different areas. However, as long as the scope and goals of virtual water and water footprint assessments are clearly laid out and acknowledged, confusion over such inconsistencies can be mitigated.
- Standardisation of virtual water reporting may help
- … Volumetric indices alone are not sufficient to determine the sustainability of water use related to any particular crop, product, company or country, but they are the most essential pieces of info
- Water footprints and stats on virtual water may be really important for multinational corporations and businesses – to help them understand how much virtual water they are importing and in what river basins their footprints are located, and what the risks are to their supply chains
- A business is going to be more secure and more profitable if you eliminate risky and unsustainable suppliers from your supply chain
- You might want to know if you’re doing business with a supplier whose water footprint and virtual water trade are really creating problems for the local water supply
- A number of major companies — SABMiller, PepsiCo and Nestlé among them — have adopted the approach – producing reports of their own virtual water usage
- Businesses are typically in a better position than governments to identify unsustainable hot spots in supply chains, where water resources are being threatened through overuse or pollution, because they know in detail where their materials and services are originating
- The problem with regulations obliging companies to report and possibly minimize virtual water usage is that “every company is different and every country is different
- [All parties and levels of society must come together] to recognize and deal with water issues
What Causes An Increase In, Or Puts Pressure On The Water Footprint?
A few factors can be:
- Population growth
- Increased total consumption
- Increased consumption of water intensive products and services
- The local and global economies
- A changing climate
- Poor water management strategies for cities as a whole
- Water pollution
Explained in more detail:
- As population size increases, so too does water use for everything – products and food included
- Using water intensive food, electricity and consumer goods increases the water footprint
- By the year 2030, experts predict that global demand for water will outstrip supply by 40 percent.
- [A changing climate has already led] to changes to the water cycle, leading to prolonged periods of drought (and, conversely, more extreme rainfall) in some areas.
- Reduced water supplies could add to water insecurity …
- … human impacts on freshwater systems can ultimately be linked to human consumption, and … issues like water shortages and pollution can be better understood and addressed by considering production and supply chains as a whole
- Water problems are often closely tied to the structure of the global economy
- Many countries have significantly externalised their water footprint, importing water-intensive goods from elsewhere. This puts pressure on the water resources in the exporting regions, where too often mechanisms for wise water governance and conservation are lacking.
- Not only governments, but also consumers, businesses and civil society communities can play a role in achieving a better management of water resources
Ways To Reduce A Water Footprint
Just a few ways across society might be:
Reducing water use
Reducing water leaks, loss and waste
Buying fewer new products and reducing overconsumption
Buying second hand
Recycling water intensive materials and products
Avoiding purchases of disposable, low-quality goods
Reducing or becoming more efficient with energy and electricity use – energy and electricity production uses a lot of water
Increasing efficient manufacturing practices, most factories have reduced water use by 12 percent since 2005, and 33 percent since 1970 (watercalculator.org)
Reduce food waste
Businesses can track and manage water usage better
More efficient agricultural irrigation systems
Water Footprints Are Often Local & Individualized
Different countries can have different water footprints for the food they produce, and products they make.
You can read more in:
- Water Footprint Of Different Products (waterfootprint.org)
- Virtual Water Of Different Products (wikipedia.org)
Importing Virtual Water, & Virtual Water Trade Between Countries
Importing water intensive products can save a country’s own water supplies.
- China is one of the biggest importers of virtual water in the world [and China also trades between it’s States]
- China is the world’s top soybean buyer, importing tens of millions of metric tons per year. And behind each ton is more than 2,000 cubic meters of water — either rainfall or irrigation — needed to grow, harvest and prepare soybeans for use. In the case of soybeans and other crops, the majority of this water is lost to the atmosphere through evaporation and transpiration during the plants’ lifetime, and none of it — save the tiny amount still hydrating the final product — actually makes it to China. Yet, to an extent, this virtual water represents an enormous volume of real water that China need not pull from its own shrinking endowment.
- Importing water intensive foods or products can be a replacement for having your own water
- It can ease stress on the countries’ own limited resources, and they can use those resources on other industries and direct consumption
- Virtual water trade refers to the idea that when goods and services are exchanged, so is virtual water.
- When a country imports one tonne of wheat instead of producing it domestically, it is saving about 1,300 cubic meters of real indigenous water.
- If this country is water-scarce, the water that is ‘saved’ can be used towards other ends.
- If the exporting country is water-scarce, however, it has exported 1,300 cubic meters of virtual water since the real water used to grow the wheat will no longer be available for other purposes.
- Water-scarce countries like Palestine discourage the export of oranges (relatively heavy water guzzlers) precisely to prevent large quantities of water being exported to different parts of the world
Global Virtual Water Trade Is Growing Over Time
By two fold, and sometimes four fold:
- The total virtual water volume associated with global food trade has more than doubled during a 22-year study period between 1986 to 2007
- International food trade has led to enhanced savings in global water resources over time by transferring commodities grown in countries that use water more efficiently — either because of more favorable climates or better technology — to less water-efficient countries; and that virtual water trade patterns had shifted substantially in some respects.
- Virtual water trade within North America quadrupled …
Examples Of Water Footprints In Different Foods & Products
We put together a guide of the water footprints of some different products and foods.
Examples of the different types of water footprints and how they make up the different food and product overall water footprints can also be seen here:
- Product Water Footprint Gallery (waterfootprint.org)
- Virtual Water Tracking Of Goods & Resources (earthmagazine.org)
Water Footprint Stats Of Different Countries
- China …
- The water footprint of Chinese consumption is about 1070 cubic metres per year per capita. About 10% of the Chinese water footprint falls outside China.
- Japan with a footprint of 1380 cubic metres per year per capita, has about 77% of its total water footprint outside the borders of the country.
- The water footprint of US citizens is 2840 cubic meter per year per capita. About 20% of this water footprint is external. The largest external water footprint of US consumption lies in the Yangtze River Basin, China.
- The global water footprint of humanity in the period 1996-2005 was 9087 billions of cubic meters per year (74% green, 11% blue, 15% grey). Agricultural production contributes 92% to this total footprint.
- The average American’s daily water footprint for all the (non-food) household goods they purchase, use and throw away is 583 gallons.
You can find more stats on water footprints and water use here (waterfootprint.org)
Water Footprint Assessment & Calculation Tools
You can find more tools for assessing and calculating water footprints here (waterfootprint.org)
There’s also a Water Footprint Calculator at GRACE (gracelinks.org)
Otherwise, what you can do with food specifically, is:
- Find out the weight of the food you are eating (e.g. an 8oz beef steak), or count the number of that item of food you are eating (e.g. two eggs)
- Google the amount of water that food takes to produce per unit of weight
- Multiply the weight or number of the food item by the litres per weight or number to get the water footprint
Why Is A High Water Footprint Not Always A Bad Thing (With Examples)?
If you are just looking at the total water used to make or deliver something – this can be misleading.
You’ve got to look at the type of water involved, and the conditions/variables for each specific water footprint.
Let’s look at some examples to see what we mean (there’s probably other examples too):
- Mainly Rain Fed Crops & Food vs Irrigated Crops & Food
Irrigation in agriculture is one of, if not the biggest freshwater user in society.
But, some types of farming such as organic farming may focus on having mainly rain-fed crops and food.
You could have an irrigated farm and rain fed farm with similar water footprints, but the rain fed one might be considered more sustainable as you don’t have to touch or deplete freshwater sources (blue water) to do it – which means more freshwater is available for drinking water, industry, power generations and households.
- Industry & Power Generation Using Recycled Waste/Grey Water vs Freshwater
Power plants and energy production (including both electricity production and refining petroleum for vehicles) requires water.
Turbines in power plants for example need a lot of water for cooling.
Power plants using ‘once through’ cooling, or using freshwater sources for cooling vs. a power plant that uses water more than once and is able to make use of treated waste water or other types of water than fresh water – would be considered more sustainable.
Watercalculator.org writes about once through and closed cycle systems
The same can be said for factories and industrial activities that can capture, treat and re-use waste and grey water.
- Water Scarce vs Water Abundant Countries & States
Ideally you’d like to minimise fresh water use if you can, but using more water in water abundant states and countries may not be as much of a problem.
Dry countries, and countries that are already water scarce would be ill advised to see having water footprints as high as water abundant countries for similar products.
Russia and Brazil for example are countries with large renewable fresh water supplies (compare that for example to dry water scarce countries in the Middle East).
Where Do The Water Footprint, & Virtual Water Concepts Come From?
- The water footprint concept, sources and methodology come from the Water Footprint Network (WFN).
- The concept was created by Dr. Arjen Hoekstra who, along with the others at the WFN, developed the framework and established the international organization as the foremost research network in the discipline.
- Tony Allan, a political geographer and Middle East scholar at King’s College London, coined the term “virtual water” in 1993 to help explain why long-predicted “water wars” driven by water and food security had not occurred among the arid nations of the Middle East and North Africa.
- Allan noted that Egypt, Israel, Jordan and other countries in the region were buying millions of tons of grain each year from water-rich countries to supplement their own food production and buoy prosperity (countries in the Middle East can save their scarce water resources by relying more on import of food).