IN light of the climate crisis, the term carbon footprint is now well known. But the concept of the water footprint, whose environmental stakes are just as high, is much less well known.
Calculated by a process similar to that of the carbon footprint, it refers to the total volume of fresh water (m³) used to produce all the goods and services we use, from A to Z, including domestic, agricultural, industrial and other uses.
Theorised in 2002 by Dutch professor Arjen Hoekstra, the water footprint aims to gauge these almost “invisible” quantities of water, in order to provide benchmarks to help governments, businesses or individuals consume in a way that minimises waste.
“It can be measured for a single process, such as growing rice, for a product, such as a pair of jeans, for the fuel we put in our car, or for an entire multi-national company,” reads the Water Footprint Network website, a platform founded in 2008 by researchers at the University of Twente (Netherlands), including Professor Hoekstra.
In addition to raising awareness about water waste and the need to save this essential resource, the Water Footprint
Network proposes a method for calculating a water footprint, taking into account three different types of water: blue water, green water and grey water.
Blue water is the best known, since it covers domestic, agricultural, energy and industrial uses. It is what we use to wash, to feed ourselves and to grow plants.
Less well known, green water is the water that is held in soil and available to plants. According to France’s National Research Institute for Agriculture, Food and Environment, INRAE, it represents 60 per cent of the mass of precipitation (versus 40 per cent for blue water). It therefore includes rainwater and is one of the nine planetary boundaries to be monitored and respected by humanity.
Grey water, on the other hand, refers to wastewater reprocessed in wastewater treatment plants.
Taking “virtual” water into account
The water footprint can be measured on the scale of an individual, a company, a city or a country. You can calculate your own by visiting the Water Footprint Network platform, which allows individuals to evaluate their water footprint by providing a few precise details, including their annual income, their country of origin and their diet.
According to the French Environment and Energy Management Agency, ADEME, French people consume an average of 148 litres of water per person per day. But this estimate only covers domestic water use (hygiene, housework, food, etc) and not the water used to produce the food they eat or the clothes they wear. For example, the production of a single T-shirt can require around 2,500 litres of water.
When the calculation is applied to a company specialising in textiles or the food industry, for example, it will take into account the amount of water needed to produce the garments or the foods in question.
This so-called “invisible” or “virtual” water consumption also applies to the calculation of a country’s water footprint, since it encompasses both the production of goods and services.
In line with a recent announcement by the French government outlining its “water plan”, the water footprint should be included in environmental labelling from 2024.
Launched by ADEME in 2022, this method aims to inform consumers about the environmental impacts of products or services. It is based on a scale similar to that used for building energy efficiency ratings, using letters ranging from A to E. – ETXDailyUp
