An Endangered Ressource

Santiago, Cape Town, Karachi, Los Angeles, Mombasa... All of these cities are preparing for "day zero", when not a single drop of water will come out of the tap. Subjected to unprecedented anthropic pressures, this resource is now amongst one of the planetary boundaries that have been crossed, which has major impacts on ecosystems, health, food resilience or peace in the world. Solutions do exist, however. There is an urgent need to rethink our relationship with water and to collectively rewrite its history.

The shortage concerns worries

100 kilometers north of Barcelona, the Sau reservoir that supplies the city and its surroundings is at its lowest level ever. Catalonia has been experiencing a drought for more than two and a half years. In the streets, posters calling for water sobriety are displayed and the first restrictions on agriculture, industry and individuals have come into force. The situation is worrying, as the report of the Joint Research Centre of the European Commission underlined in March 2023. Indeed, its combined drought index has gone into the red for Catalonia as for many other territories. Not only are there summer droughts, but now winter droughts are a reocurring reality as well - water is becoming a constant concern.

Today, according to UN-Water, 2.3 billion people live in water-stressed countries, including 733 million at high or critical levels. About 4 billion people, i.e. almost 2/3 of the world's population, suffer from a severe water shortage for at least one month of the year. Dry rivers, lakes at historically low levels, insufficient snow accumulation on the summits, forest fires from spring onwards... The reality is becoming more obvious every year.

The myth of inexhaustible groundwater reserves

Unlike surface water, whose scarcity is visible to man, groundwater, which accumulates as a result of rainfall, is very difficult to measure. It represents the primary source of daily water supply for a quarter of the world's population and some water tables cover very large areas. In South America, for example, the Guarani aquifer extends over four countries and is estimated to contain up to 40,000 km3 of water.

These reservoirs are undergoing massive extraction across the globe. One of the regions that pumps the most groundwater is the Asia-Pacific region, where 7 of the 10 most extracting countries account for 60% of all withdrawals. But these territories are far from being exceptions and more than 20% of the world's aquifers are overexploited. In Europe, every year the volumes withdrawn exceed the level of precipitation. The aquifers have been decreasing continuously since the beginning of the 2000s and the pace is accelerating. Globally, groundwater withdrawals have tripled in 50 years (between 1970 and 2020). A rarefaction of the resource, invisible, but real.

Green water, a planetary boundary/limit exceeded

Among the nine planetary limits/boundaries initially identified in 2009 by researchers from the Stockholm Resilience Center, the use of freshwater was not a matter of concern since it did not exceed the critical threshold established. However, this diagnosis only took into account the so-called blue water (lakes, rivers and groundwater). But a study published in Nature last year has raised the crucial importance of green water. This water, absorbed by plants and present in the soil and in biomass, stands actually at a much more worrying level. The study shows that green water is the sixth planetary boundary that humanity has breached. It plays several fundamental roles for the planet and for living beings, such as diluting pollutants, preserving biodiversity and mitigating floods through wetlands.

Multiple water pollution

Beyond the quantitative aspect, the quality of the resource is also a major concern. Antibiotics, hormones, microplastics, synthetic fertilizers, heavy metals, chemicals of all kinds..., water is loaded with multiple pollutants all along its journey. A study published last August in the journal Environmental Science and Technology, identifies the presence of toxic synthetic products exceeding the thresholds of recommendations in water. These are called, in technical language, the "PFAS" (for "per and polyfluoroalkyl") and their planetary boundary has already been exceeded too. Even rain is contaminated... The main author of the study, researcher and professor at the University of Stockholm Ian Cousins, makes a clear statement: "There is nowhere on Earth where rainwater would be safe to drink, according to the data we have used.” Whether we are in Tibet or on the Marquesas Islands, rainwater is polluted and therefore not drinkable!"

Climate change - the main culprit

In February 2022, the sixth IPCC report highlighted the impact of climate change on freshwater resources worldwide. Scientist