With water increasingly scarce, sustainable management has become essential to preserving both the quantity and quality of this vital resource. The estimates that “at least one in four people will live in a country with chronic or recurring fresh water shortage by 2050”.

According to the French Environment and Energy Management Agency (ADEME), average water consumption in France stands at 148 litres per person per day. While the figure speaks for itself, this is only so-called ‘domestic’ consumption – the water we use for drinking, washing, looking after the house or watering the garden. However, the cars we drive, the household appliances and energy we use, the clothes we wear and food we consume all need a large volume of water for their production.

Developed analogously to the concept of the environmental footprint, the water footprint aims to gauge the volumes of water used to fulfil the needs of a population (food, clothing, housing, transport, etc.) to quantify the pressure that human usage – both direct and indirect – places on the resource. It aims to improve water management policies.

To this end, it factors in virtual water, the water we consume indirectly, which has considerable impact on availability of the resource on our planet.

Virtual water: definition

Virtual water is the water required for the end-to-end production of the goods and services consumed by populations, whether the goods are local or imported. This water usage can neither be seen directly, nor is it visible in the end product. However, it is essential to the manufacturing, distribution or transportation of the product, so is consumed ‘indirectly’. In meat production for example, volumes required are considerable with water being used to hydrate the animals, irrigate the feed crops, clean facilities at the farm, process the meat, and so on.

Why this concept? Simply because it highlights the invisible or hidden amounts used by humans. It helps to more precisely measure the water footprint of a country, organisation or individual; in other words, the pressure actually exerted on this precious resource by our lifestyles and, more broadly, by human activities whether domestic, industrial, agricultural, commercial and tourist.

Different methods for calculating the water footprint

Until 2006, approaches to calculating the water footprint were purely volumetric, the best-known undoubtedly being the Water Footprint Network method, developed by Arjen Hoekstra. This calculated the volumes needed to manufacture a product, irrespective of the type of water – blue (irrigation), green (precipitation) or grey (used to dilute pollutants) – or where it was consumed.

The volumetric approach has developed to include the actual amount consumed (not returned to the natural environment), local water stress (from a geographical and seasonal perspective, as not all regions have the same amount of fresh water available) and the effects of water scarcity on ecosystems, human health and resources for future generations.

The water footprint now accounts for all impacts relating to the consumption and pollution of the resource, in a life cycle assessment (LCA) extending from the extraction of raw materials through to the processing, transportation, usage and end-of-life of a product. It factors-in the volumes consumed and emission of pollutants to assess the impact of water scarcity and pollution of aquatic environments on human health, the health of ecosystems and the availability of water for future generations. Blue water becomes an indicator of water scarcity, green water is dispensed with and grey water is replaced by LCA pollution indicators (ecotoxicity, eutrophication, toxicity to humans, etc.).

The AWARE (Available WAter REmaining) method is recommended by the United Nations Environment Programme (UNEP) and the Product Environmental Footprint (PEF), developed by the European Commission. Since 2016, ISO 14046 has provided guidelines aiming to standardise water footprint measurement.

Virtual water consumption in numbers

Results will differ depending on the method of calculation used (for example the Water Footprint Network developed by Hoekstra, or AWARE).

However, in its Illustrated Guide, the French National Research Institute for Agriculture, Food and Environment (INRAE) suggests the following volumes:

  • 1,300 litres for a T-shirt, equivalent to 70 showers.
  • 3,100 litres to manufacture a washing machine.
  • 30 litres to produce a hamburger.

Accordingly, through the import and export of agricultural products and manufactured goods, the trade in virtual water is a means of offsetting shortages by redistributing the resource globally, enabling countries where the resource is low to consume water-intensive products they would otherwise be unable to produce (so protecting their food security), for example.

The impact of virtual water on water management and the environment

By importing goods and services, the consuming countries outsource not only the production of these goods and services, but also the risk of water shortages. As such, the virtual water trade raises the issue of sustainable management of the resource.

For example, according to the annual report of the French Ministry for the Ecological Transition (key figures on water and aquatic environments, 2020 edition), France’s water footprint is more than double the amount of the resource drawn domestically. This means that more water is consumed abroad to produce the goods and services imported into France than is required to produce the goods and services exported from France.

As a result, importing countries use water taken not from their own resources, but from regions that may be arid and experiencing water stress. In so doing, they can increase pressure on vulnerable areas, which often have no conservation policies for this rare resource.

Virtual water is essential for calculating water footprint

The water footprint is a strategic tool for tackling increasing water scarcity, structuring management policies and encouraging sustainable production and consumption practices. This is subject to the condition however that it factors in water consumed ‘virtually’.

Virtual water helps to calculate the volume of water actually consumed in the form of goods and services exchanged internationally and to distinguish the major flows between the various regions of the world. By including this in the calculation, the water footprint can quantify the impact of actual consumption on global water availability, and can be used to determine the environmental sustainability of lifestyles, agricultural practices and industrial activities.

This enables us to address the issues facing the water sector and to better manage this vital resource for the future of the planet.



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