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Understanding water to protect it better: the work of the Geosciences Centre

Published on 22 March 2026

Water shapes our landscapes, sustains our ecosystems and shapes our societies. Yet behind this seemingly unchanging public good lies a highly complex system, sensitive to climatic variations, human activities and biological processes invisible to the naked eye. To mark World Water Day, Mines Paris – PSL is highlighting the work of Nicolas Flipo, a lecturer and researcher at the Centre for Geosciences, whose research helps to better understand, model and predict the functioning of continental hydrosystems for the sustainable management of this resource.

Water: a dynamic and invisible system

When we talk about water resources, we naturally think of rivers, lakes or groundwater. But these systems never operate in isolation. Water circulates constantly between the surface, the subsurface, the atmosphere and living ecosystems, carrying with it matter, energy and chemical elements.

It is precisely this integrated view of water that Nicolas Flipo focuses on. A hydrologist and hydrogeologist by training, he studies the fate of water resources across different regions, the exchanges between surface water and groundwater, the biogeochemical processes taking place within them, and their response to climatic and anthropogenic drivers. The aim: to provide robust scientific tools to inform public policy decisions and support the transition towards more sustainable water management.

Simulation of nitrate concentrations (mg/L) in the groundwater of the Seine-Normandy basin. Produced using the CaWaQS modelling tool, developed at the Centre for Geosciences, this map shows nitrate concentrations in the region’s main aquifers, in the areas most vulnerable to surface pollution. The values shown correspond to a simulation at the end of 2022 and illustrate the spatial distribution of this type of major contamination. Map by Nicolas Gallois.

Climate change: far-reaching effects on groundwater

One of the key issues addressed recently is the impact of long-term climate variability on groundwater levels. A recent study, conducted in collaboration with M2C – Continental and Coastal Morphodynamics – UMR 61430, CNRS – University of Rouen Normandy, shows that interannual and decadal climate fluctuations can cause variations of several metres in groundwater levels in the Seine basin.

These findings are crucial: they reveal that subtle changes in rainfall variability can increase the frequency and severity of groundwater droughts or, conversely, groundwater-related flooding. A better understanding of these mechanisms enables us to anticipate future risks and adapt the management of drinking water, agriculture and infrastructure.

Microscopic life in water: a climate and environmental issue

In situ sensors now enable high-frequency measurements of water quality, particularly of dissolved oxygen in rivers. Whilst this data is invaluable, conventional models often assume constant biological parameters, even though the activity of microorganisms varies over time.

To address this limitation, as part of multidisciplinary research conducted at the Centre for Geosciences, in collaboration notably with Thomas Romary and PhD students Shuaitao Wang and Masihullah Hasanyar, the ProSe-PA software was developed. This unique tool uses methods to assimilate dissolved oxygen measurements with the RIVE biogeochemical model to estimate changes in the physiological properties of microbial communities present in river waters, such as phytoplankton and bacteria.

This approach significantly improves the simulation of dissolved oxygen, particularly during algal blooms, with parameters consistent with the scientific literature. However, there is still scope for improvement in better integrating the latest-generation sensors to enable more precise monitoring of organic matter fluxes, which are one of the drivers of microbial activity and strongly influence oxygen concentrations during low-flow periods.

Observe, share, decide: science serving society

Beyond fundamental research, Nicolas Flipo is involved in innovative observation systems, such as the MOLONARI ecosystem, which measures water and energy exchanges between rivers and their beds in situ. He has also contributed to the international SWOT satellite mission (NASA/CNES), designed to observe surface waters on a global scale.

This integration of observations, modelling and dialogue with public stakeholders illustrates the commitment of Mines Paris – PSL: to produce rigorous, open and useful science, capable of informing collective decisions in the face of water-related challenges.

Understanding water better to protect it more effectively

In an era of climate change and the increasing scarcity of certain resources, Nicolas Flipo’s work highlights a scientific and societal truth: we can only properly protect what we understand. By revealing the hidden dynamics of hydrosystems, Mines Paris – PSL is actively helping to build a more resilient water management system, one that is equal to the challenges of the 21st century.