Large natural deposits are found in the glaciers of Greenland and the Antarctic and in Lakes of North America or Russia. Humid, tropical zones contain high percentages of the total world reserve. In other zones, it is necessary to take advantage of every drop in order to survive. It has been calculated that a man needs 50 liters or more daily in order to satisfy his personal and home needs. In developed countries, we use an average of 400 to 500 liters of water per person daily.
Water is a valuable and scarce resource.
We have seen that only a small portion of the planet's water is fresh. If we use our rivers and our seas as dumps for our trash and waste, more and more we will have less, and if water is life, more and more there will be less life. Acid rain, dumped wastewater, agricultural chemical products, heavy metals, etc., are incorporated into the river water volume. A river has a limited capacity for self-purification, and when this is surpassed, water becomes dangerous for human consumption, the aquatic flora and fauna die, the landscape is degraded. In lakes and subterranean waters, the problem is greater since they have very slow natural cycles, so that they take a long time to expel the polluting agents.