Index: p. 365-367.

The end of the 20th century was marked by increasing global awareness of the importance of preserving the environment. The 21st century now faces great challenges, one of which is providing drinking water to all inhabitants of the planet. Due to runaway population growth and pollution, pure water is becoming rarer and rarer. Water, source of life and of death, ally or enemy, is inextricably associated with the history of mankind. It is a vital resource that we must learn to manage and distribute. Many conflicts in the modern world are, upon closer examination, linked to water ownership. For the past few decades, we have been living through wars over black gold, but wars over blue gold are already taking place. Hydrogeology is relevant to many aspects of society. And yet, even though there is no more commonplace action than opening a faucet or flushing a toilet, the provenance of that water often remains cloaked in mystery. Tortuous passageways, immense subterranean lakes, dowsing rods, pendulums, all populate our fellow citizens' tales. Pagnol1 is not so distant when one sees local authorities prefer the dowser to the hydrogeologist when deciding on the future of their community; one then understands the enormity of the work yet to be done in shaking the obscurantism that persists over this field, which is nevertheless so important to us.