The Earth is currently the only known planet where water is present all at once in its liquid, solid and gaseous forms. Rather than providing an exhaustive account of current research on this topic, this CNRS Info supplement aims to highlight certain aspects of the recent research, primarily on fresh water, carried out by the CNRS in France and elsewhere. The study of polar ice has enabled paleoclimatologists to reconstitute the history of the Earth's climate over a period of several hundred thousand years, and thus to predict future climate change with greater accuracy. Since water vapor has an impact on the greenhouse effect, climatologists are studying the atmospheric part of water cycles and biosphere-atmosphere exchanges in order to improve their understanding of the factors controlling climate.
Liquid water is both a resource and lifeblood.
It is rare and precious, and essential to agriculture, industry and domestic consumption. Its quality must therefore be preserved and its use must be managed. The biological diversity of streams and lakes depends on the quality both of water and related infrastructures. Biological indicators must be established in order to assess the state of health of these hydrosystems. Indeed, in some areas, water has become a source of conflict, and appropriate ways of managing such situations must be sought.