The irrigation corresponds 73% of the water consumption, 21% for use of the industries and only 6% destine it the consumption domesticate. The ambient degradation elapses of the uncontrolled population growth and the superexploration of natural resources. In 1940, 30% of the Brazilians liveed in the cities, today 81% live in the great urban centers, and great part is in the areas of sources, generally slum quarters, that is, busy areas in secrecy, arrive and go destroying forests and crowded in the springs of the rivers and playing its lixos and sewers without any care, with this the water are each time more poluda compromising the exploitation of the same one for the consumption. In devoid countries the water scarcity will affect the food production if they will not be adopted measured urgent to raise the hdrica productivity. The water scarcity crosses borders because of the international trade of cereals. To produce a ton of these foods consumes a thousand tons of water, thus to import them is the way most efficient to import water.
Some countries use cereals to balance its hdricas accounts in similar way, to commercialize them in the future in certain way, to make it with the water of the future. The water lack already harms the harvests in some countries, between them China, world-wide producing greater of cereals. To prevent the water scarcity a commission of the organizations of United Nations of 1987 suggests: – To limit the population growth; – To guarantee feeding in long stated period; – To preserve biodiversity and ecosystems; – To diminish the energy consumption that uses renewable source; – To increase the industrial production in the countries not industrialized to the technology base ecologically adapted; – To control the wild urbanization, to make the integration between lesser field and cities; – To guide the politics of necessary actions, also to include mechanisms natural of rain water exploitation; – The dessalinizao of sea water.