Freshwater is a scarce resource; its annual availability is limited and demand is growing. The water footprint of humanity has exceeded sustainable levels at several places and is unequally distributed among people. Good information about water footprints of communities and businesses will help to understand how we can achieve a more sustainable and equitable use of fresh water.

There are many spots in the world where serious water depletion or pollution takes place: rivers running dry, dropping lake and groundwater levels and endangered species because of contaminated water. The water footprint helps to show the link that exists between our daily consumption of goods and the problems of water depletion and pollution that exist elsewhere, in the regions where our goods are produced. Nearly every product has a smaller or larger water footprint, which is of interest for both consumers that buy those products and businesses that produce, process, trade or sell those products in some stage of their supply chain.

The Water Footprint Network aims to come to broadly shared global standards on water footprint accounting. We try to prevent what has happened in the case of the carbon footprint: a multitude of different definitions, approaches and methods, so that it is difficult to properly assess claims in this field. A unique set of global standards on the water footprint will make efforts of businesses and communities that strive for a reduction of their water footprint more transparent.

The Network has two work programmes: a technical and a policy work programme. Within each programme there are several projects. Many of the projects are executed by our partners and just run under the umbrella of the WFN to ensure fruitful exchange with other activities within the network. Some projects aim at further research and development, other projects aim at practical application of the water footprint in various settings. In addition there are activities that purely aim at communication, exchange and dissemination.

Yes, we will look how we can help you best, e.g. by linking you to another organisation within our network, by providing training, by carrying out some research ourselves or by offering to review your results.

Ideally, the relation works in two directions. The network helps you to find out how you can best apply the water footprint in your organisation. Your organisation feeds its experiences back into the network, so that others can profit as well. In this way you help to develop global standards and sector-specific guidelines on water footprint accounting.

Consumers can reduce their direct water footprint (home water use) by installing water saving toilets, applying a water-saving showerhead, closing the tap during teeth brushing, using less water in the garden and by not disposing medicines, paints or other pollutants through the sink.

The indirect water footprint of a consumer is generally much larger than the direct one. A consumer has basically two options to reduce his/her indirect water footprint. One option is to substitute a consumer product that has a large water footprint by a different type of product that has a smaller water footprint. Examples: eat less meat or become vegetarian, drink tea instead of coffee, or even better drink plain water. Not wearing cotton but artificial fibre clothes saves a lot of water. But this approach has limitations, because many people don’t easily shift from meat to vegetarian and people like their coffee and cotton. A second option is to stick to the same consumption pattern but to select the cotton, beef or coffee that has a relatively low water footprint or that has its footprint in an area that doesn’t have high water scarcity. This requires, however, that consumers have proper information to make that choice. Since this information is generally not available in the world of today, an important thing consumers can do now is ask product transparency from businesses and regulation from governments. When information is available on the impacts of a certain article on the water system, consumers can make conscious choices about what they buy.

Businesses can reduce their operational water footprint by saving water in their own operations and bringing water pollution to zero. Keywords are: reduce, recycle and treat before disposal. For most businesses, however, the supply-chain water footprint is much larger than the operation footprint. It is therefore crucial that businesses address that as well. Achieving improvements in the supply chain may be more difficult – because not under direct control – but they may be more effective. Businesses can reduce their supply-chain water footprint by making supply agreements with certain standards with their suppliers or by simply changing to another supplier. In many cases it probably means quite something, because the whole business model may need to be transformed in order to incorporate or better control supply chains and to make supply chains fully transparent to consumers. Among the various alternative or supplementary tools that can help improving transparency are: setting quantitative water-footprint reduction targets, benchmarking, product labelling, certification and water footprint reporting.

Traditionally countries formulate national water plans by looking how to satisfy water users. Even though countries nowadays consider options to reduce water demand in addition to options to increase supply, they generally do not include the global dimension of water management. In this way they do not explicitly consider options to save water through import of water-intensive products. In addition, by looking only at water use in the own country, most governments have a blind spot to the issue of sustainability of national consumption. As a matter of fact many countries have significantly externalized their water footprint without looking whether the imported products are related to water depletion or pollution in the producing countries. Governments can and should engage with consumers and businesses to work towards sustainable consumer products. National water footprint accounting should be a standard component in national water statistics and provide a basis to formulate a national water plan and river basin plans that are coherent with national trade policy and national environmental policy.

As a consumer, your water footprint is sustainable when (a) the total remains below your equal share of the available freshwater resources in the world, and (b) no component of the total water footprint presses at places where or times when local environmental flow requirements are violated.

This is a question that we receive from people that are familiar with the idea of carbon offsetting. In the case of carbon it doesn’t matter where mitigating measures are taken, so one can offset own CO2 emissions by helping to reduce CO2 emissions or enhancing carbon sequestration elsewhere. In the case of water, this is different, because water depletion or pollution in one place cannot be compensated by whatever measure in another place. The focus should therefore be on reduction of the own water footprint, at the places where and times when this water footprint causes problems. We should do all that is ‘reasonably possible’ to reduce the own water footprint, both the direct and indirect one. This holds for both consumers and businesses. Only in second instance, when everything has been done to reduce the own water footprint, one can consider offsetting. This means that the residual water footprint is offset by making a ‘reasonable investment’ in establishing or supporting projects that aim at a sustainable, equitable and efficient use of water in the catchment where the residual water footprint is located. The terms ‘reasonably possible’ and ‘reasonable investment’ include normative elements that need further quantitative specification and about which we need to reach societal consensus.

Generally the price paid for water is far below its real economic cost. Most governments subsidise water supply on a huge scale by investing in infrastructure like dams, canals, distribution systems, and wastewater treatment. These costs are often not charged to the water users. As a result, there is insufficient economic incentive for water users to save water. Besides, due to the public character of water, water scarcity is generally not translated into an additional component in the price of goods and services that are produced with the water, as happens naturally in the case of private goods. Finally, water users generally do not pay for the negative impacts that they cause on downstream people or ecosystems.

No, some components of the water footprint can have negative environmental impacts, but other components may be without any problem. Besides, it deserves consideration whether one has a total water footprint below or beyond one’s equal share of the available freshwater resources in the world.

The water footprint shows the plain volumes of water consumption and pollution, including where and when, in all phases of the supply-chain of a product. This is interesting from two perspectives. First, the water footprint tells the total water volume apparently appropriated for a certain product. Since freshwater availability on earth is limited it is important to know how it is allocated over various purposes, to feed debates such as water for nature versus food, water for food versus energy, or water for basic needs versus luxury goods. Besides, it is interesting to see how water is shared among people. Second, the water footprint forms the basis for a detailed impact assessment. The water footprint map (showing where and when what volumes of water are being appropriated) is the basis for assessing the local impacts of the various water footprint components. For this purpose the water footprint map can be overlaid with a map showing local water stress. In this way one can identify the hotspots where water footprint reduction is most urgent.

There is no general answer to this question, because it depends on the product, available technology, local context, etc. Besides, one has to keep in mind that the question includes a normative element, which implies that it needs to be answered in a societal-political context. A few general things can be said, however. First of all, one has to distinguish between reduction targets with respect to the green, blue and grey water footprint. As for the grey water footprint, which refers to water pollution, one can demand a reduction to zero for all products, at least in the long term. Pollution is not necessary. A zero grey water footprint can be achieved by prevention, recycling and treatment. Only thermal pollution (by water use for cooling) is difficult to reduce to zero. The blue water footprint in the agricultural stage of products can often be brought down by a factor two by reduction of consumptive water losses; in the industrial stage it will depend very much on the sector and what has already been done. Technologically, industries can fully recycle water, so that the blue water footprint can everywhere be reduced to the amount of water that is actually being incorporated into the product. Benchmarks can be developed for specific products by taking the performance of the best producers as a reference. Another general rule for any water footprint mitigation strategy is to avoid the water footprint pressing in areas or times where environmental flow requirements are violated. A final rationale for a water footprint mitigation strategy can be the fair sharing of water resources. This may be the basis for water footprint reduction particularly for large water users.

The two concepts nicely complement each other, each concept addressing another environmental issue: the carbon footprint addresses the issue of climate change, the water footprint relates to the issue of freshwater scarcity. In both cases, a supply-chain perspective is promoted. There are also differences, however. For a carbon emission it doesn’t matter where it happens, but for a water footprint is does matter. A carbon emission in one place can be offset by carbon emission reduction or sequestration in another place, which is not true for water: one cannot reduce the local impact of water use in one place by saving water in another place.

Desalination of salt or brackish water can only be a solution for freshwater scarcity in a limited number of applications, not because one cannot obtain the right quality of water for all purposes, but because desalination requires energy, another scarce resource. In fact, desalination is a way of substituting one scarce resource (freshwater) by another one (energy). If at a certain spot the freshwater issue is pressing even more than the energy issue, one can decide in favour of desalination, but in general it doesn’t make sense to propose desalination as a general solution to freshwater scarcity. Besides, apart from the energy argument, desalination is still expensive, too expensive for use in agriculture where most of the water is used. Finally, salt or brackish water are only available along coasts, which means that bringing desalinated water elsewhere would imply additional costs (again including energy).

In a world where many products are related to water depletion and pollution it is very useful to make the history of products more transparent. It is good to have the facts publicly available, so the consumer has a choice. Information can be provided on a label or can be made available through internet. This is most useful for products that often have large effects on water, like products that contain cotton or sugar. For consumers it would be helpful to integrate a water label in broader labels that include other issues as well, like energy and fair trade. Ideal would be a world in which we don’t need labels because we can trust that all products meet strict criteria.

The term “footprint” is often used as a metaphor to refer to the fact that humanity appropriates a significant proportion of the available natural resources (land, energy, water). However, just like the “ecological footprint” and the “carbon footprint”, the “water footprint” is more than a metaphor: there is a rigorous accounting framework with well-defined measurable variables and well-established accounting procedures to calculate the water footprints of products, individual consumers, communities, nations or businesses. We discourage people to use the water-footprint concept as a metaphor, because its strength lies in its effectiveness when used in a context of strict accounting and measurable reduction targets.

Water is a renewable resource, but that does not mean that its availability is unlimited. In a certain period, precipitation is always limited to a certain amount. The same holds to the amount of water that recharges groundwater reserves and that flows through a river. Rainwater can be used in agricultural production and water in rivers and aquifers can be used for irrigation or industrial or domestic purposes. But in a certain period one cannot use more water than is available. A river can be emptied and in the long term one cannot take more water from lakes and groundwater reservoirs than the rate with which they are recharged. The water footprint measures the amount of water available in a certain period that is consumed (i.e. evaporated) or polluted. In this way, it provides a measure of the amount of available water appropriated by humans. The remainder is left for nature. The rainwater not used for agricultural production is left to sustain natural vegetation. The ground- and surface water flows not evaporated for human purposes or polluted is left to sustain healthy aquatic ecosystems.

The methods for water footprint accounting have been published in peer-reviewed scientific journals. In addition, there are also practical examples available of how one can apply the methods to calculate the water footprint of a specific product, an individual consumer, a community or a business or organisation. In generic sense there is agreement about the definition and calculation of a water footprint. However, every time one applies the concept in a situation not done before new practical questions arise. These are practical questions like: what should be included and what can be excluded, how to deal with situations where the supply chain cannot be properly traced, what water quality standards to use when calculating the grey water footprint, etc. Discussion therefore focuses on how to handle those practical issues. There is also still discussion about the precise method of how to estimate the local impacts of a water footprint.

Freshwater availability on earth is determined by annual precipitation above land. One part of the precipitation evaporates and the other part runs off to the ocean through aquifers and rivers. Both the evaporative flow and the runoff flow can be made productive for human purposes. The evaporative flow can be used for crop growth or left for maintaining natural ecosystems; the green water footprint measures which part of the total evaporative flow is actually appropriated for human purposes. The runoff flow – the water flowing in aquifers and rivers – can be used for all sorts of purposes, including irrigation, washing, processing and cooling. The blue water footprint measures the volume of groundwater and surface water consumed, i.e. withdrawn and then evaporated. The grey water footprint measures the volume of water flow in aquifers and rivers polluted by humans. In this way, the green, blue and grey water footprint measure different sorts of water appropriation. When necessary, one can further classify the water footprint into more specific components. In case of the blue water footprint, it can be considered relevant to distinguish between ground and surface water use. In case of the grey water footprint, it can be considered valuable to distinguish between different sorts of pollution. In fact, preferably, this more specific pieces of information are always underlying the aggregate water footprint figures.

It depends on the question that one would like to address. The green water footprint measures total evaporation and is meant to feed the debate about the allocation of water to different purposes in a context of limited availability. Information about increased or reduced evaporation is relevant from the perspective of catchment hydrology and potential downstream effects.

Research has shown that crops can sometimes result in increased evaporation when compared to natural vegetation (particularly in the period of rapid crop growth), and other times in reduced evaporation (e.g. because of soil deterioration or reduced aboveground biomass). In many cases the differences are not very significant at basin scale. The change in evaporation is interesting from the perspective of catchment hydrology and potential downstream effects, but not for the debate on how limited freshwater resources are allocated over different purposes. The water footprint is designed for the latter debate. The purpose of the green water footprint is to measure human’s appropriation of the evaporative flow, just like the blue/grey water footprint aims to measure human’s appropriation of the runoff flow. The green water footprint measures the part of the evaporated rainwater that has been appropriated by human being and is therefore not available for nature. The water footprint thus expresses the cost of a crop in terms of its total water use.

The aggregate water footprint of a product, consumer or producer shows the total volume of fresh water consumed or polluted annually. It serves as a rough indicator, instrumental in awareness raising and for getting an idea of where most of the water goes. The water footprint can be presented as one aggregate number, but in fact it is a multidimensional indicator of water use, showing different sorts of water consumption and pollution as a function of space and time. For developing strategies for sustainable water use, one will need to use the more detailed layer of information embedded in the composite water footprint indicator.

The idea of ‘weighing factors’ sounds like an attractive idea, because not every cubic metre of water used has the same impact. However, we strongly discourage this approach for three reasons. First, weighing is and will always remain very subjective, because there are many different sorts of impacts, some of which cannot even be easily quantified. Second, impacts are always fully local-context dependent, which means that it is impossible to design universally valid weighing factors. As a matter of fact, the impact of one cubic metre of water withdrawn from one particular point in a river at a certain point in time depends on the characteristics of that river, like the volume and variability of water flow in the river, the competition over water at that point in the river at that particular moment and the effects of withdrawal on downstream ecosystems and other users. Third, weighing would take away the beauty of the current approach, namely that the water footprint figures actually mean something (they refer to actual volumes of water used).

In order to properly address the fact that different water footprint components do indeed have different impacts, we emphasize that the water footprint is a multidimensional indicator, showing volumes, but also the type of water use and the locations and timing of water use. The aggregate water footprint figure is always composed of various components, so that one can precisely tell where and when what type of water is used or polluted. ‘Water footprint accounting’ means that one quantifies the water footprint in all its details. This forms the proper basis for an impact assessment, in which one assesses the various impacts for each separate water footprint component in time and space. Obviously, the impact assessment will show that the impact is different for each separate water footprint component. For formulating water policy aimed to reduce water footprint impacts it is more useful to know how different water footprint components link to various impacts than to have a weighed water footprint indicator. The risk of making a seemingly advanced weighed water footprint indicator is that such indicator hides all information related to impacts instead of making the impacts explicit. Some people have suggested that weighing has been successful in other fields, like the weighing of different greenhouse gasses by looking at their so-called ‘global warming potential’. Suffice here to say that the cases are simply not similar, which makes copying the idea of weighing a thoughtless thing to do.

The water footprint can be an indicator in the life cycle assessment (LCA) of a product. Being applied in an LCA is one of the many applications of the water footprint. In an LCA, the multi-dimensional, spatial explicit water footprint should first be overlaid with a water-stress map in order to arrive at a spatial-explicit water footprint impact map. The various impacts should subsequently be weighed and aggregated in order to arrive at an aggregated water footprint impact factor. For LCA an important question is how impacts can be aggregated – which is a specific requirement for LCA and not relevant to other applications of the water footprint. Other applications of the water footprint are for example identifying hotspot areas of the water footprints of certain products, consumer groups or businesses, and formulating response strategies to mitigate water footprint impacts. For those purposes aggregation is not functional, because specification in type of water and space-time is essential in those applications.

The water-footprint concept is part of a larger family of concepts that have been developed in the environmental sciences over the past decade. A “footprint” in general has become known as a quantitative measure showing the appropriation of natural resources or pressure on the environment by human beings. The ecological footprint is a measure of the use of bio-productive space (hectares). The carbon footprint measures the amount of greenhouse gases produced, measured carbon dioxide equivalents (in tonnes). The water footprint measures water use (in cubic metres per year). The three indicators are complementary, since they measure completely different things. Methodologically there are many similarities between the different footprints, but each has its own peculiarities related to the uniqueness of the substance considered. Most typical for the water footprint is the importance of specifying space and time. This is necessary because the availability of water highly varies in space and time, so that water appropriation should always be considered in its local context.

The water footprint is a term that refers to the water used to make a product. In this context we can also speak about the ‘virtual water content’ of a product instead of its ‘water footprint’. The water footprint concept, however, has a wider application. We can for example speak about the water footprint of a consumer by looking at the water footprints of the goods and services consumed or about the water footprint of a producer (business, manufacturer, service provider) by looking at the water footprint of the goods and services produced by the producer. Furthermore, the water footprint concept does not simply refer to a water volume only, like in the case of the term ‘virtual water content’ of a product. The water footprint is a multidimensional indicator, not only referring to a water volume used, but also making explicit where the water footprint is located, what source of water is used, and when the water is used. The additional information is crucial in order to assess the impacts of the water footprint of a product.