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Human activities are always linked to water use. At a global scale, most of the water use occurs in agricultural production (approx 90%), followed by the industrial and finally the domestic sectors. Water use occurs through irrigation, bathing, washing, cleaning, cooling, processing, transportation, etc. These activities can result in the pollution of water. The Water Footprint quantifies the usage of water by human activities in terms of volumes. Moreover, it considers where, when and what kind of water sources are used. This information is then used to assess the sustainability of an activity i.e. whether a certain product/person/nation etc. contributes to specific hotspots of water scarcity or pollution as well as social and economic consequences. By assessing the sustainability of the impact, response strategies can be formulated to directly target activities that lead to water scarcity and pollution. Consequently, Water Footprint Assessment can be used to improve water source protection and SSWM. Virtual Water is a similar concept to the Water Footprint but looks only on volumes and is applicable to products only.
The water footprint of a product is an empirical indicator of how much water is consumed, when and where, measured over the whole supply chain of the product (see also using indicators to measure progress and performance). Thus, the water footprint is a multidimensional indicator, showing volumes but also making explicit the type of water use (evaporation of rainwater, surface water or groundwater, or water pollution) and the location and timing of water use.
Water is known to be a renewable resource as it is cycling through the environment (see water cycle). So, why do we bother making a water footprint? For almost all human purposes such as drinking, irrigation, energyproduction, transportation, cooking, washing, etc. freshwater is needed. Salt water, which dominates the earth’s surface and the available water resources, cannot be used for these purposes (see also the water cycle or introduction to water sources). Even though freshwater is a renewable resource, it is not unlimited and counts for only about 3% of the earth’s water resources. Most of these 3% are not directly accessible; water in lakes and river accounts for less than 0,01% of global water resources.In a certain period, precipitation is always limited to a certain amount and water can get scarce. The same holds true for the amount of water that recharges groundwater reserves and that flows through a river. In these periods, one cannot use more water than the amount that is being recharged into the water body (see also water balance estimation, water resources assessment, or water allocation). As humankind is strongly dependent on freshwater, making a water footprint can help identifying products that can be risky to produce at a certain location and at a certain period of time.The water footprint of humanity has exceeded sustainable levels at several places and is unequally distributed among people. A water footprint canhelp achieve a more sustainable and equitable use of fresh water. More possibilities to optimise water use can be found in the section on water use for households, industry and agriculture.
As already mentioned, the concept of water footprint cannot only be used for products (as is the case with virtual water) but can also be applied to persons, businesses, communities, nations, geographically delineated areas and for humanity in total.
Possible applications are:
Depending on the application, different units are calculated with a water footprint:
Volume per unit of time
Volume per unit of time per capita
Volume per unit of time / volume per unit of time divided by turnover
Geographically delineated area
Volume per unit of time
Volume per unit of time per capita
Various standards for water footprints exist. Probably the most well-known standard is the Global Water Footprint Standard developed by the Water Footprint Network (WFN). The International Organization for Standardization (ISO) is currently working on a procedural standard on how to incorporate water footprint in a product Life Cycle Analysis (LCA). This ISO standard will be linked to the Global Water Footprint Standard. While the ISO 14046 is still a draft and expected to become a standard in 2014, the WULCA working group (a group of researchers from North America, Europe and Australia) is currently working on a methodology for this standard. Find more information on the methodology on the group’s website.
The Global Water Footprint Standard accounts for:
The green water footprint is the consumption of water that refers to precipitation on land that does not run off or recharge the groundwater but is stored in the soil or temporarily stays on top of the soil or vegetation. Green water is usually used for crop growth. The green footprint includes:
The grey water footprint is an indicator of the degree offreshwater pollution that can be associated with a process step or a product or consumer, etc.It is the volume of freshwater that is required to assimilate the load of pollutantsbased on natural background concentrations and existing ambient water qualitystandards.
In terms of the water used to make a product, the water footprint can also be referred to as the product’s virtual water content. Virtual water is the total amount of water, which has been used to produce a good as well as the water indirectly used (e.g. the water required to produce the feed for an animal when calculating the water footprint of the animal’s meat). It is called virtual because the final good no longer contains the amount of total water, which was used to produce it. The two differences between virtual water and a water footprint are that:
Comparing agricultural products, animal products generally have a larger water footprint than crop products both for litres per ton as well as per calorie. The average water footprint per calorie for beef is twenty times larger than for cereals or starchy roots. This large difference is due to various factors. Firstly, animals need more time to grow and then they need to be fed: 98% of the water footprint of animals refers to the feed for the animals (HOEKSTRA 2012).
Traditionally, national water plans are made in order to plan the provision of sufficient water to all water users. Yet, this national view neglects the “imported water” that is attached to a product that was produced outside of the country. Externalising a nation’s water footprint by importing a lot of “water-intensive” products threatens the sustainability of a national consumption, as they might be attached to depletion and pollution of the producing country. Also, this might increase the dependency on foreign freshwater resources.
Consumption of agricultural products largely determines the global water footprint related to consumption, contributing 92% to the total water footprint. Consumption of industrial products and domestic water use contribute 4.7% and 3.8% respectively.
The total water footprint per year per capita varies, among others, by differences in consumption patterns: countries with high consumption of bovine meat – one of the highly water-intensive commodities – usually also have a higher national water footprint. It can also vary due to the water consumption and pollution per unit of product per country, e.g. in the USA, the average water footprint of one kg of consumed bovine meat is 14500 m3/ton, while in the UK this is 9900 m3/ton (MEKONNEN & HOEKSTRA 2011).
The Water Footprint itself provides us with mere facts on the quantity, location, time and kind of water source.
Yet, the important information we want to retrieve from calculating the Water Footprint is to find out whether the impact of the Water Footprint is sustainable! This is done with the help of the Water Footprint Sustainability Assessment.
A Water Footprint Assessment is conducted as follows:
The severity of the environmental impact of water consumption and pollution can be assessed by comparing the water footprint of a product/person/nation etc. with the availability of water in the affected water bodies at the location and time of withdrawal. Water Risk Maps can be used as a basis for comparison. Find a selection of Water Risk Maps under Weblinks below. It is also informative to assess whether a certain product/person/nation etc. contributes to specific hotspots of water scarcity or pollution, but also whether it contributes unnecessarily to the global water footprint of humanity.
A Water Footprint Sustainability Assessment does not only assess the environmental impact of a product/person/nation etc. but also the social and economic impact. By assessing the impact, response strategies can be formulated to directly target activities that lead to water scarcity and pollution.This way, water footprint assessment can be used to improve water source protection and sustainability of water use.
HOEKSTRA, A.Y.; CHAPAGAIN, A.K.; ALDAYA, M.M.; MEKONNEN, M.M. (2011): The Water Footprint Assessment Manual. Setting the Global Standard. London/Washington: Earthscan. URL [Accessed: 03.09.2013]. PDF
MEKONNEN, M.M.; HOEKSTRA, A.Y. (2011): National Water Footprint Accounts. The Green, Blue and Grey Water Footprint of Production and Consumption. (= Value of Water Research Report Series, 50). Delft: United Nations Educational, Scientific and Cultural Organization-Institute for Water Education (UNESCO-IHE). URL [Accessed: 03.09.2013]. PDF
HOEKSTRA, A.Y. (2012): The Hidden Water Resource Use Behind Meat and Dairy. In: Animal Frontiers 2, 3-8. URL [Accessed: 03.09.2013]. PDF
CHAPAGAIN, A. K.; HOEKSTRA, A.Y. (2004): Water Footprints of Nations - Volume 1: Main Report. (= Research Report Series No. 16, 1). Delft: UNESCO-IHE, Institute for Water Education. URL [Accessed: 12.10.2010]. PDF
The study tries to analyse and to collect the water footprints of nations. The water footprint of a nation consist of the total amount of used domestic water resources plus the virtual water flows entering the country minus the flows leaving the country.
MEKONNEN, M.M. ; HOEKSTRA, A.Y. (2010): A Global and High-resolution Assessment of the Green, Blue and Grey Water Footprint of Wheat. In: Hydrology and Earth System Sciences 14, 1259-1276. URL [Accessed: 12.10.2010]. PDF
A paper which deals with the virtual water content of wheat. The assessment is made on a global level and includes the exploring of green, blue and grey water used during wheat production.
This document contains information about Switzerland’s role in the global virtual water trade.
WBCSD (Editor) (2009): Water for Business. Initiatives guiding sustainable water management in the private sector. Geneva: WBDSC and IUCN. URL [Accessed: 19.10.2010]. PDF
The future of any business depends on the sustainability of water resources, which are increasingly under pressure. At the same time, consumer awareness and investors' increased scrutiny of corporate water risks have resulted in stronger expectations that companies should reveal their ‘water performance'. To respond effectively, the business community needs guidance, tools, standards and schemes to enable change to more sustainable practices. This is what this publication aims at providing.
MEKONNEN, M.M.; HOEKSTRA, A.Y. (2012): A Global Assessment of the Water Footprint of Farm Animal Products. In: Ecosystems 15, 401-415. Luxembourg: Springer-Verlag. URL [Accessed: 04.09.2013]. PDF
This paper provides a comprehensive account of the water footprint of animal products, considering different production systems and feed composition per animal type and country.
MEKONNEN, M.M.; HOEKSTRA, A.Y. (2011): The Green, Blue and Grey Water Footprint of Crops and Derived Crop Products. In: Hydrology and Earth System Sciences 15, 1577-1600. Goettingen: Copernicus Publications. URL [Accessed: 09.09.2013]. PDF
This study quantiﬁes the green, blue and grey water footprint of global crop production in a spatially-explicit way for the period 1996–2005.
KEKERITZ, T. (2010): Water Footprint. Virtual Water Embedded in Products. Enschede: Water Footprint Network (WFN). URL [Accessed: 09.09.2013]. PDF
This poster visualises the water footprint of twelve selected commodities.
The poster shows the water footprint of daily life and options for reduction.
This presentation provides a short introduction to the concept of water footprinting.
http://www.waterfootprint.org/ [Accessed: 09.09.2013]
The Water Footprint Network provides explanations, publications, case studies and its own framework for waterfootprinting. You can also find the free Water Footprint Assessment Tool online.
http://www.wulca-waterlca.org/ [Accessed: 24.09.2013]
This is the website of the WULCA working group. This group works as an international working group focusing on water use assessment and water footprinting taking the life cycle perspective. The WULCA working group’s overall goal focuses on providing practitioners, from both industry and academia, with a coherent framework within which to measure, assess and compare the environmental performance of products and operations regarding freshwater use.
http://waterriskfilter.panda.org/ [Accessed: 09.09.2013]
This tool allows quantifying water-related risks for all industries in all countries.
http://aqueduct.wri.org/ [Accessed: 09.09.2013]
This tool by the World Resources Institute measures and maps water risks around the globe.
http://www.wbcsd.org/ [Accessed: 09.09.2013]
This tool by the World Business Council for Sustainable Development (WBCSD) is designed for companies and organisations to map their water use and assess risks relative to their global operations and supply chains.