Résumé
Among the water resources on earth, groundwater is a resource hidden in the rocks of the earth's crust. For various reasons, notably the fact that this water is not directly visible but also as a consequence of education and longstanding traditions, the properties and physical laws governing groundwater are not well known outside the circle of hydrogeologists, the scientists specialists of the survey, management, and protection of groundwater resources. This resource has lots of advantages, notably when compared to surface water, and is thus largely used worldwide for many purposes: agriculture, tap water, industries, bottling, etc. In fact, this resource is available year-long, even during the dry season and in arid countries, and is well protected from surface contaminations. It needs, however, to be appropriately managed and protected to ensure its sustainability (quantity and quality). Thus, this study intends to provide the basics of the groundwater science, "hydrogeology." It is illustrated by examples taken from the Evian Natural Mineral Water, that is groundwater, and the way it is managed and protected. The groundwater resource is a sustainable water resource belonging to the earth's water cycle, which flows thanks to the natural energy provided by the sun. The main physical processes of the groundwater water cycle are the infiltration of rainwater into the soil, its slow flow within the pervious rocks from the earth's crust, called "aquifers," and finally its natural outflow at springs and into rivers. It can also be reached with man-made wells and pumped. Groundwater contains dissolved minerals that are mostly the results of interactions between the water and the aquifers' rocks.