Historic droughts in France, Mediterranean heatwaves, empty reservoirs in parts of Spain, and international tensions over water sharing in river basins such as the Nile or the Mekong:
freshwater is now at the center of environmental crises. In September 2023, a global warning was issued:
the planetary boundary for freshwater has been crossed.
This means that humanity now exceeds sustainable thresholds
in the use of two essential resources:
• Blue water, which refers to water withdrawn from rivers, lakes or aquifers to irrigate crops, supply industries, produce energy or meet domestic needs;
• Green water, which refers to rainwater absorbed by soils and used by vegetation before naturally evaporating.
To shed light on these issues, Nicolas Flipo, hydrologist, biogeochemist and modeller, Director of Research at the École des Mines de Paris, provides his insights by answering five essential questions.
1. How is the water cycle disrupted today?
The water cycle is based on constant exchanges between oceans, atmosphere and continents. Each year, about 500,000 km³ of water evaporates from the oceans and 450,000 km³ falls back as rain.
The deficit (50,000 km³) is compensated by continental precipitation. Plants continuously evaporate water due to heat, around 70,000 km³ annually, which circulates in the atmosphere and returns as rain along with fluxes from ocean surfaces.
“Today, humanity has become one of the major drivers of climate evolution, disrupting the relative stability of the Holocene and pushing us into a new climate era fully controlled by our activities, with major consequences for the water cycle,” explains Nicolas Flipo.
Human activities—deforestation, intensive agriculture, urbanization, industrialization—modify rainfall distribution, soil quality, and thus water availability. The result is entire regions shifting into permanent water stress, a situation where water demand persistently exceeds available resources. Globally, more than one billion people already live in areas with chronic deficits.
2. Which human activities consume the most water?
Agriculture is the main consumer of freshwater, accounting for about 80% of global withdrawals. Irrigation requires huge volumes of water, often pumped from groundwater, with direct impacts on strategic reserves.
“Agricultural water is 80% green water, because it is the plants themselves that consume and transpire it into the atmosphere.”
The energy sector is the second largest user: water is used to cool thermal and nuclear power plants. In Europe, this represents about 30% of blue water use, compared with only 5% at the global scale. Industry (textiles, electronics, food processing) and domestic uses (drinking water, hygiene) complete the picture. But there is an often-overlooked distinction:
“Water that is withdrawn is not always consumed. A power plant may withdraw large amounts of water for cooling, but return it to the environment, whereas agricultural irrigation consumes almost all it withdraws, as the water returns to the atmosphere.”
3. What risks does this create for businesses and territories?
Water scarcity generates systemic impacts:
• On agriculture and food, with harvests threatened by droughts and declining groundwater levels.
• On energy, with power plants forced to reduce output due to insufficient cooling, as happened with nuclear reactors in Europe during the summer of 2022.
• On industry, particularly in water-intensive sectors such as textiles or electronics.
“The digital economy may also be challenged by water shortages, since data centers and microchip production require colossal volumes of extremely pure water,” adds Nicolas Flipo.
The water footprint of products is becoming a strategic issue. A cotton T-shirt requires 2,500 liters of water, while 1 kg of red meat can require up to 10,000 liters (compared to 1,000 liters for 1 kg of vegetables). “Our water footprint extends beyond borders,” explains Flipo. France, for example, imports “virtual water” via Brazilian soy used for livestock feed, creating pressures elsewhere in the world.
4. What solutions can restore the water cycle?
The top priority remains mitigating climate change, since every degree of warming increases droughts and hydrological extremes. “Stabilizing the climate is key. Adaptation will not be enough if temperatures keep rising.”
On the ground, several levers exist:
• Slowing runoff with hedgerows, grass strips, and agroforestry to promote soil infiltration.
• Restoring wetlands and floodplains to recharge aquifers.
• Reducing losses and waste in agriculture and urban water networks.
• Moving towards more plant-based diets, since “reducing animal protein intake can cut the water footprint by tenfold.”
For businesses, this means rethinking value chains and pooling efforts with territorial actors. “Water management cannot be individual. It must be collective and territorial,” stresses Nicolas Flipo.
5. What scientific perspectives and innovations lie ahead?
Research is moving toward integrated models, capable of linking the water cycle to food, energy and industrial systems.
“We are working on modeling transition scenarios that integrate water flows, climate and human uses.”
On the technology side, desalination and ultrafiltration plants are expected to multiply, despite their energy costs and ecological impacts.
“In some island or arid regions, desalination is already the only viable solution. But it must be powered by renewable energy to reduce its carbon footprint,” notes Nicolas Flipo.
The key also lies in territorial reorganization: companies must collaborate with local authorities to restore flood expansion zones, slow water flows, and share resources.
The water crisis is not only an environmental issue: it is a systemic crisis that engages agricultural, energy, economic and social models. In a world constrained by planetary boundaries, water becomes a critical factor of resilience.
Nicolas Flipo concludes: “We cannot make it rain. But we can slow, store, and reorganize water. That is where our power to act lies.”
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About the expert
Nicolas Flipo is Director of Research at the École des Mines de Paris, part of Université Paris Sciences et Lettres.
A hydrologist, biogeochemist and modeller, he studies interactions between the water cycle, climate dynamics and human pressures.
He led for ten years, until 2024, the interdisciplinary program PIREN-Seine,
which investigates water resources in the Seine basin, the largest groundwater reservoir in Europe, in the context of global change.
His research focuses on multi-scale modeling of water flows and stocks, the evolution of water uses at the territorial level,
and quantifying impacts linked to agriculture, energy and urbanization.
A recognized specialist in systemic approaches, he develops multi-scale modeling tools to connect the physical, ecological and social components of the hydrological cycle.
He actively contributes to research on water footprints, planetary boundaries, and nature-based adaptation strategies.
