In light of the climate crisis, the term “carbon footprint” is well known. But the concept of a “water footprint”, the environmental stakes of which are just as high, is much less well known.
Calculated by a process similar to that of carbon footprint, it refers to the total volume of fresh water (m³) used to produce all the goods and services we use, including domestic, agricultural, industrial and other uses.
Theorised in 2002 by the 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 multinational company,” reads the Water Footprint Network (WFN) website, a platform founded in 2008 by researchers at the University of Twente (Netherlands), which includes Hoekstra.
In addition to raising awareness about water waste and the need to save this essential resource, WFN 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, as it covers domestic, agricultural, energy and industrial uses. It’s what we use to wash, feed ourselves, and grow plants.
Less well known is green water, the water that is held in soil and available to plants. It represents 60% of the mass of precipitation (vs 40% 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 treatment plants.
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 WFN 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 next year.
Launched by Ademe in 2022, this method aims to inform consumers about the environmental impacts of products or services, based on a scale similar to that used for building energy efficiency ratings, using letters ranging from A to E.