On trips terrestrial water cycle, which basically include the freshwater inland reserves (lakes, glaciers, subsurface, etc.) play a key role as regulators. Without them, the natural flowing water would be as irregular as meteoric precipitation inputs that engender and there would be no permanent water reservoir. Early studies on reserves and the quantification of volumes focused on understanding its regulatory function and to evaluate the possibilities of mobilizing take advantage of renewable water resources uneven. Among the various reserves, while large lakes and glaciers are effective regulators in the basins where they are, underground water tables and aquifers are much more frequent, with most regular flowing water on every continent, estimated at 12 billion m3 / year on average (ie 30% of the total flow of the rivers in the world, estimated at 40 billion m3 / year, (4 'is due to underground water courses. In fact, water permanent surface waters which have circulated on the first floor and the subsoil.

Mine Water independent of the water cycle. To what extent and under what conditions natural water reserves can be used not only as regulators, but operated as non-renewable resources, style deposits of mineral raw materials (including oil, gas, minerals, etc.)? In general, the distinction between renewable and nonrenewable resources is well defined: some are in the form of flux and reproduce or regenerate naturally, the others are reservations not reconstituted human scale. In the case of water, nature offers both flows and stocks, and the distinction between renewable and nonrenewable resources depends on the length scale of human economic activities.