A water footprint is one way of measuring or expressing the water required for something.
In this guide, we explain explain in further detail what a water footprint is, how it can be used, and also what virtual water is.
Summary – Water Footprints, & Virtual Water
One concept or tool used by some organisations and individuals to do this is a water footprint
A simplistic way of defining a water footprint is the amount/volume of water it takes to produce or do something
It can be measured for anything that requires water – food, a t shirt, a car, running electricity for a specified period of time, or even the water footprint of an entire country
There’s a number of ways to express a water footprint – total volume of water used, per capita water used, water used per weight of production, and so on
Calculations might take into account only withdrawn or consumed water, but can also take into account water lost (or not recoverable) to evaporation, contamination and pollution, and other water that becomes unusable or is removed from the water supply
A water footprint can include water used for the entire lifecycle/lifetime of something, or just one or several stages of the lifecycle (material production, manufacturing, use phase, and end-of-life disposal + any other stages)
Water footprints can be made up of direct and indirect water use, which is also called visible and invisible water.
Direct water is water that is used on site or seen by the user
Indirect water is unseen, and is usually used off site somewhere else up or down the supply and production chain
Virtual water is the same or very similar to indirect and unseen water
Water footprints can calculate water use generally, but some footprints split up blue, green and grey water use
Blue water is water from surface water and ground water sources
Green water is rainfall
And, grey water is water used to dilute waste water
Not all types of water are of equal value, and some are far more renewable and sustainable than other from a resource depletion perspective
There’s a difference between withdrawn and consumed water
Withdrawn water is usually returned to the water source after use
Consumed water is usually permanently removed from the water supply
Different countries and regions can have different water footprints for the same type of product – beef is one example of this because farming systems and processes (and resource inputs) can differ from place to place. The same can be said for different crops which might need more water in climates that are dry and hot
Similar to the use of carbon footprints, there are a number of limitations with using a water footprint, and we’ve listed these limitations below
Because of the limitations of water footprints, several sources indicate that they are a general tool only, and that other more advanced water usage tools and processes should be used in an integrated approach when making key water management decisions
Corporations however might find some use in water footprints
Some countries have used the concept of water footprints for help in forming regulations and policies, whilst other countries have taken the opposite approach
Water footprints can be exported and imported between countries and even States and territories (or provinces) via trade
This allows more water efficient and water abundant countries to trade to countries who are less water efficient or more water scarce
Trans boundary sharing or trading of water resources is also possible (Australia is an example of a country that does transboundary water trading between States and territories)
What Is A Water Footprint?
In simple terms, a water footprint is one representation of the amount/volume of water it takes to produce, or do something.
It can be one reference tool for getting an idea of how much total water something uses, or how much of a specific water type of water (blue, green, grey) something uses.
The watercalculator.org and waterfootprint.org resources in the list below have further definitions of what a water footprint is.
Calculating A Water Footprint
A water footprint can be expressed in many ways – usually total volume of water used, but can also be expressed in terms of water used per weight of production, per dollar of production, per gram of protein produced, per calorie produced, and more
Some calculations might only take into consideration withdrawn and consumed water
Other calculations might also include evaporated water, polluted/contaminated water, and any other water that becomes unusable (such as degraded water, or water that needs to be treated for re-use), or is immediately removed from the water supply.
What Things Can Have A Water Footprint?
A water footprint can apply to anything that uses water.
A few examples might be:
– A piece of food
– A product like a t shirt, or pair of shoes
– An activity like washing hands, or flushing a toilet
– It can even apply to an entire country, and each country might have their own water footprint to consider and compare
– Other wide applications of a water footprint might be for an individual’s food diet, or for whole households, companies, and cities
A Lifecycle vs Individual Stages
A water footprint can take into account either:
– An entire lifecycle
– Or, a specific stage of a lifecycle (or a selection of stages)
A few examples of different life cycles and stages of different products are:
– A car
A car is made up of materials that have to be sourced and/or refined (such as steel, rubber, plastic, leather, foam, etc).
A car is then manufactured, including not only the body of the car, but different parts like the tires.
A car is then driven and needs to be maintained – including re-fuelling, servicing, repairs, modification, cleaning, and so on
A car then reaches the end of it’s life at some point, and make go to the scrap heap.
… while manufacturing for example might be one stage of a car’s life cycle, all of the above stages can be added together to get a more accurate view of a car’s lifecycle water footprint.
– A unit of electricity
Electricity can be sourced from different energy sources, with one being coal
Coal has to first be mined
Coal might then be refined
Coal is then combusted for energy at a coal power plant
Coal energy then has to be converted to electricity, travel through the power grid, and can then be used in buildings and at home
… the water used at the power plant might be one stage of the coal energy electricity water footprint, but, the entire lifecycle includes all stages, and will have a much larger water footprint when considering water used in mining, etc.
thewaterweeat provides a good example of the water hidden in a piece of beef
The vast majority of it comes from the feed required to feed cattle, and the remainder comes from water the cattle need to drink, and finally water for servicing farmhouses and slaughterhouses.
Direct vs Indirect Water (& Visible & Invisible Water)
Direct water use is the water we see, or that is used on site somewhere.
Indirect water can also be called invisible water, because it’s used indirect either further up the supply/production chain, or off site somewhere.
An example of indirect water is that most industries and homes use electricity.
The water footprint of electricity is usually classified as indirect or invisible water use, because it took water to produce that electricity off site, before it could be used further down the supply chain elsewhere at another location.
What Is Virtual Water?
Virtual water is the hidden water that is not felt or seen, that goes into making something.
It’s essentially the same thing as indirect or invisible water
watercalculator.org gives an example of a smartphone having a large virtual water footprint:
… 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.
Apart from watercalculator.org, waterfootprint.org and wikipedia.org also discuss the concept of virtual water.
The Types Of Water In A Water Footprint
The three main types of water that can be categorized in a water footprint might be:
– Blue water
The amount of surface water and ground water used.
It can be used directly, or evaporated.
– Green water
The amount of rainfall used.
It can be used directly, or evaporated.
– Grey water
The amount of freshwater used to dilute waste water from manufacturing.
Diluted waste water usually has to meet water quality standards determined by regulations in the area.
These water footprints can be categorized separately, or can be added together for a total water footprint.
They can give a more accurate idea of what is happening in terms of water management in a specific area.
Green water might be most preferable from a sustainability perspective, but blue water can be used sustainably in areas with consistent rainfall and larger natural supplies of freshwater.
Wikipedia.org also indicates that [Not all water types or sources are of] equal value
The watercalculator.org, waterfootprint.org, and earthmagazine.org resources listed all go into greater detail explaining each of these types of water in a water footprint.
The waterfootprint.org, and earthmagazine.org resources both give examples of how the types of water make up different shares of different products. earthmagazine.org also further discusses how China, Mongolia etc. use blue, green and grey water in their article
As one example for beef from waterfootprint.org:
The production of one kilogramme of beef requires approximately 15 thousand litres of water (93% green, 4% blue, 3% grey water footprint).
[But] There is a huge variation around this global average [and it] … depends on factors such as the type of production system and the composition and origin of the feed of the cow.
Withdrawn vs Consumed Water
There’s a difference between withdrawn, and consumed water, in a water footprint.
Withdrawn water is water that is used, but returned to the water supply.
An example of withdrawn water is water used for hydroelectricity that is returned to the river after it’s use.
Consumed water is water that is removed permanently from the water source.
Consumed water might be considered as non recoverable water.
An example of water consumption is the water used to irrigate crops, that is either absorbed, or evaporated.
One example of consumptive water use vs withdrawals, according to watercalculator.org, is:
… agriculture accounts for 38 percent of the [United States’] freshwater withdrawals but it accounts for approximately 80 to 90 percent of the nation’s consumptive water use
Water Footprints For The Same Type Of Product Can Differ Between Countries
It’s interesting to note that the exact same type of product can have a different water footprint in one country compared to another.
This is the case with beef and other food products, where variables like the predominant farming systems used, climate, and other factors, can lead to different water footprints in different products.
waterfootprint.org and wikipedia.org discuss this in further detail, and give examples.
Limitations Of Using A Water Footprint As A Water Measuring Tool
There can be a number of limitations to using a water footprint to measure water use.
These limitations mainly relate to the variables, factors, and challenges involved in calculating a water footprint, and also the limited nature of one purely volumetric measure of water used.
A decision to use water may also take into account a range of social, economic and environmental considerations, and not just the environmental side.
For these reasons, a water footprint should be one of many tools used to measure water use, and not the only tool.
Water footprints are a general estimate or reference only, and might be looked at to get an idea of general water use trends, and to make general comparisons. They may be best used in an integrated approach with other far more advanced and detailed water usage stats, tools and information, whilst also weighing up other relevant factors.
They are not a comprehensive or catch all calculation or tool.
Several sources suggest they shouldn’t carry any real relevance when making key water management decisions at the government level (or a similar level).
Some of the limitations might include:
– Not all water footprints have the same exclusions and exclusions, or are calculated and composed the same way
Some water footprints may just include the water usage for one stage of a lifecycle, whilst some may include the water for a whole lifecycle.
Additionally, some water footprints may only include blue water use, whereas others may include all three of blue, green and grey water use.
There can be other instances of inclusions and exclusions, and methods of calculation, like these.
Because of this, comparing different water footprints can become unreliable, and some water footprint figures may be inaccurate (if they don’t include all water use)
– Data collection can be expensive and challenging
It’s not always possible to collect all water use data for a particular process or product.
Sometimes, it’s impossible to collect water use data because none is available, or some is unavailable (due to restrictions or not enough resources).
In this instance, a water footprint may only tell part of the water use picture, and not all of it.
– Water footprints tend not to make a distinction between water use in water abundant and water scarce regions
Not all water use is unsustainable.
Water use in a water abundant region with either large volumes of natural water supplies, or consistent rainfall, generally isn’t going to be as unsustainable as water use in water scarce regions with smaller natural water supplies, and a dry, arid and hot climate.
From this perspective, the same water footprint number for the same type of product might be sustainable in one region, but not in another. But, water footprints don’t tend to make this distinction.
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).
– Water footprints tend not to make a distinction about good or poor water management in an area
In addition to water abundance or scarcity, the management of water supplies in a city or geographic region are important.
Water use may not be as unsustainable if the city has a good water management plan in place, and has a history of sustainably managing their water supplies.
A water footprint tends not to make this distinction though.
– Water footprints don’t represent other local variables, context, and the various tradeoffs (pros and cons) of water use in a geographic area
Water is used as a resource, and the use of water has tradeoffs (pros and cons).
Therefore, not all water use is bad.
Further to this, each local area will have different tradeoffs to their water use.
One example of where it may be acceptable to use water in areas with scarce water supplies is in low income regions.
Water use in this instance can provide local jobs and entire livelihoods to people i.e. there are socioeconomic benefits.
[Sri Lanka is an example of a place where rain is abundant, and people depend on water for employment and their livelihoods] (earthmagazine.org)
A water footprint generally does not take into account the pros and cons of water use, or the local conditions and context of water use – it usually only provides a single water footprint number.
A water footprint usually doesn’t outline the other inputs and resources used to produce or do something, and doesn’t outline the opportunity cost of doing something else with the water in a geographic region.
There’s many many factors that can be considered in regards to water use in a region (economic, social, environmental, and also relating to the use and management of other resources other than water)
– Doesn’t make a distinction between better or worse water use
Some water use might be better than others
Some examples might include using rainwater (which is renewable) over irrigated water for crop farming, using recycled water or abundant saltwater over freshwater for once through cooling at power plants (Watercalculator.org writes about once through and closed cycle systems), and using water in water abundant vs water scarce areas.
– There may not be a distinction between exported and imported water footprints
Another factor a purely volumetric water footprint may not take into account is what portion of total water use is imported water, and what part is exported water
Some countries produce and export a lot more products and goods than others, and some countries import and consume a lot more goods
When you consider that a country could be more water scarce than another, but have to use a much higher % of their available fresh water supplies for exports, a water footprint that doesn’t communicate this point may do a poor job of outlining the real picture when it comes to sustainability in this regard
– Does not explain environmental harm or the impact of alternate uses of water
[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]
[A water footprint] fails as an indicator of environmental harm nor does it provide any indication of whether water resources are being used within sustainable extraction limits.
earthmagazine.org discusses the limitations of a water footprint in greater detail. Read more about this issue in that resource.
globalwaterforum.org, globalwaterforum.org and wikipedia.org also discuss the issue of the limitations of a water footprint in their resources
How A Water Footprint Might Ideally Be Used
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.
earthmagazine.org goes into far more depth about how water problems might ideally be solved, and how water footprints can be changed to be a tool/method of measurement to help address that. A few points they discuss are (paraphrased):
Patterns of water use happen on the local level (like cities), and not as much the country or global level
So, water footprints and solutions to water problems need to be solved on the local level, for individual cities, and their sources of water
Factors like what water is being used for, the value being created, what a city is getting for their water use, how effective the water use is, and other factors like water dependency should be incorporated into water measurements
The types of water that make up a water footprint should be reported
The stages of the supply and production chain included in the water footprint should be specified
Confusion can be largely eliminated, and inconsistencies minimized, if the scope and goals of the virtual water footprint assessment are clearly laid out in a brief
Standardization of virtual water reporting may help
Water footprints may be of use to corporations (if they produce their own reports) – to understand where their water comes from, to help them identify potential risk, and help them understand various other things about their water use
Businesses may be in a better position than governments to pick up unsustainable water use, or other water issues (like overuse and pollution), because they have more data on where the materials and things that use water are coming from
Every country, and every company, faces a different set of challenges in managing water use – this is where regulations on reporting on, and managing water use, can be ineffective
Examples Of The Use Of Water Footprints By Countries
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]
Importing & Exporting Water Footprints
earthmagazine.org makes note that some arid, dry and water scarce countries can get around their water problems by importing most of their water footprint for food (like wheat for example) from water rich countries
One example of this is China importing soybeans according to earthmagazine.org, and ‘… countries like Palestine discourage the export of oranges (relatively heavy water guzzlers) precisely to prevent large quantities of water being exported’ according to wikipedia.org
Wikipedia.org also notes that ‘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.’
In regards to how much of a country’s water is sourced externally, one set of data by Wikipedia.org indicates:
China – About 10% of the Chinese water footprint falls outside China.
Japan – Has about 77% of its total water footprint outside the borders of the country.
US – About 20% of [its] water footprint is external. The largest external water footprint of US consumption lies in the Yangtze River Basin, China.
Global Water Trade Is Growing Over Time
earthmagazine.org outlines that virtual water volume associated with global food trade has doubled from 1896 to 2007, and virtual water trade in the US has quadrupled.
More favorable climates and also technology might be a few reasons that less efficient or more water scarce countries trade.
The overall result might be better water efficiency between countries.
Examples Of Water Footprints In Different Foods & Products
A few examples of water footprints in foods and products are:
waterfootprint.org and earthmagazine.org also have other examples in their resources
Per Capita Water Footprints Of Different Countries
Wikipedia.org outlines that the US has a much higher per capita water footprint than China or Japan:
The water footprint of Chinese consumption is about 1070 cubic metres per year per capita.
Japan with a footprint of 1380 cubic metres per year per capita.
The water footprint of US citizens is 2840 cubic meter per year per capita.
Water Footprint Assessment & Calculation Tools
You can find more tools for assessing and calculating water footprints at waterfootprint.org
There’s also a Water Footprint Calculator at GRACE (gracelinks.org)