Water

Water (Latin aqua) is a substance whose molecule is made up of two atoms of hydrogen and one of oxygen (H2O). The term water generally refers to the substance in its liquid state, although it may be in its solid form called ice, and in its gaseous form called vapor. It is a fairly common substance in the universe and the solar system, where it is mainly in the form of vapor or ice. It is essential for the survival of all known forms of life.

Water covers 71% of the surface of the earth's crust. It is mainly located in the oceans, where 96.5% of the total water is concentrated. Polar glaciers and ice caps account for 1.74%, while underground deposits (aquifers), permafrost and continental glaciers account for 1.72%. The remaining 0.04% is distributed in descending order among lakes, soil moisture, atmosphere, reservoirs, rivers and living beings.2 Water circulates constantly in a cycle of evaporation or transpiration (evapotranspiration), precipitation and displacement towards the sea. The winds carry in the clouds like water vapor from the sea and in the opposite direction so much water as the one that is poured from the rivers in the seas, in an approximate amount of 45 000 km³ a year. On the mainland, evaporation and transpiration contribute 74 000 km³ per year, resulting in total rainfall of 119 000 km³ per year.3

Approximately 70% of freshwater is estimated to be devoted to agriculture.4 Water in industry absorbs an average of 20% of world consumption, being used in refrigeration, transportation and solvent work in a wide variety of industrial processes. Domestic consumption absorbs the remaining 10 percent.5 Access to drinking water has increased over the past decades in virtually all countries.6 7 However, FAO studies estimate that one in five developing countries will have problems Water shortages before 2030; In these countries it is vital to reduce water expenditure in agriculture by modernizing irrigation systems.