THE WATER ROUTES

The water cycle is one of the biogeochemical cycles that take place on our planet. As water flows over and into the rocks and sediments of the Earth, it collects and carries soil particles and other sediments, as well as mineral salts and other organic and inorganic chemical compounds dissolved in it.

The oceans are salty due to the transport of salts from the mainland over millions of years, salts that remain in the sea when the water evaporates.

The water cycle is one of the life cycles of the Earth system. Water travels continuously between different reserves through physical processes. A reserve represents the water contained in one of the different steps of the cycle. The largest reserve is represented by the OCEANS, which collect 97% of the planet's water. But there is also water in solid form from glaciers. The one contained in organisms represents the smallest reserve. Physical processes are the changes in physical state (liquid, gaseous and solid) that accompany the continuous exchanges of water between the atmosphere, geosphere (earth's crust) and hydrosphere. The science that studies the water cycle is hydrology.

The volume of fresh water reserves, particularly those available for use by humans, is called WATER RESOURCE. But each reserve, on average, contains water only for a certain period of time called RESIDENCE TIME which we can consider a measure of the average age of the water contained in that reserve. Groundwater can spend over 10,000 years under the surface of the soil and, if the residence times are particularly long, become FOSSIL WATER. The water stored in the soil remains there for a short time, because it is distributed in a thin layer over the entire surface of the continents and is rapidly lost by evaporation, transpiration, surface flow or infiltration into the underground aquifers. When water evaporates from the surface of seas and oceans or from the mainland, it remains in the atmosphere for an average of 12 days before falling back to the ground or sea.

Water is essential for survival, therefore human history is inextricably linked to this resource. The availability of drinking water has always represented a very important parameter for the choice of building a city or any human settlement. Cities have linked their birth or development to the presence of rivers and sources of drinking water.

The scientific and technological evolution has led man in the last two centuries to an unprecedented industrial and demographic development that have gradually determined an increasing need for fresh water. Water is used, in addition to nutritional purposes, in agriculture and industry. Water, fresh or salt, is often the recipient of treated and untreated wastewater. This substance, in addition to not being uniformly distributed on the territory, is certainly not unlimited and often requires adequate works to be made available for multiple uses and in multiple places. So although water is infinitely recyclable and therefore inexhaustible, what actually changes are its quality (potability) and its quantity (availability). Each passage of physical or chemical state requires time, whether it is a few seconds or thousands of years, if only natural processes are taken into account. But the need to have water availability in ever greater quantities and of good quality force man to use increasingly expensive exploitation or purification processes, thus determining its value on the market. The substance essential to man and the ecosystem in which he lives is both abundant and available or scarce and unavailable. The water resources on Earth are in fact distributed in a very irregular way. Of all the countries in the world, only 11 have 50,000 or more cubic meters of fresh water per year per inhabitant, while the majority have less than 5,000 cubic meters.

So if we take into account that producing 1 kg of beef requires about 16 000 liters of water, 140 liters for a cup of coffee and 900 liters for 1 kg of corn, we can understand how the water market is most important in the world.

Each year, approximately 247,000 million m3 of water are extracted from the EU's surface and groundwater reserves (streams, lakes and rivers).

A large share of the extracted water (44%) is used for cooling processes in the energy production sector, and flows for the most part into rivers. The processes related to agriculture and food production also demand their share, using 24% of the water extracted, a percentage that in some southern regions can rise up to 80%. Many highly profitable farms operate on a small portion of irrigated land. In Spain, for example, over 60% of the total value of national agricultural production originates from 14% of agricultural land subject to irrigation.

17% of the water extracted is destined for public supply (domestic users, the public sector and small businesses) and 15% is used for industrial purposes. Half of the water used for productive uses is used in the chemical sector and in oil refineries, while most of what remains goes to the metallurgical, food and paper industries.

Directive 2000/60 / EC (Water Framework Directive) which establishes a framework for community action in the field of water has introduced an innovative approach in European legislation on water, both from an environmental and administrative-managerial point of view. . The directive pursues ambitious objectives: to prevent qualitative and quantitative deterioration, to improve the status of water and to ensure sustainable use, based on the long-term protection of available water resources. Directive 2000/60 / EC aims to achieve the following general objectives:

• expand the protection of water, both surface and underground;

• achieve the status of "good" for all waters by 31 December 2015;

• manage water resources on the basis of river basins independently of administrative structures;

• proceed through an action that combines emission limits and quality standards;

• recognize the right price for all water services that takes into account their real economic cost;

• make citizens aware of the choices made on the matter.