Water is the most important resource on Earth; it is able to change our planet in geological and landscape terms and it is thanks to its presence and abundance that it has been possible for life to emerge. Water is the most abundant chemical compound on Earth, it is found in all environments and is an integral part of all living organisms. Our planet is about 70% water, while only 30% is land. Seen from space, the Earth appears as a blue planet.

Water is the most important resource on Earth; it is able to change our planet in geological and landscape terms and it is thanks to its presence and abundance that it has been possible for life to emerge. With its 10 trillion cubic metres, water covers more than 70% of the Earth's surface while only 30% is occupied by dry land. Seen from space, the Earth appears as a blue planet. The first cellular life forms appeared in the oceans some 3.5 billion years ago, only 1 billion years after the birth of our planet, and they have changed over time into more and more complex forms, colonising the land too, but still depending on water: there is no life without water. All living beings are made up of water in percentages ranging from 50% to over 95% (in some organisms such as jellyfish).

The vast majority of water on Earth, 97%, is sea water or salt water, unusable for drinking, but used for working, irrigating and most industrial uses. The remaining 3% is fresh water, and therefore potentially drinking water, a resource that is becoming increasingly precious to the point of being defined as 'blue gold'. Most of fresh water is found in glaciers and perennial snow (68.7%), and is not available for human consumption, while 30% is confined underground in groundwater aquifers, up to tens of metres deep, from which water of high purity and quality can be drawn, but only if pumps or other facilities are available. Only 0.3% is easily accessible in rivers and lakes.

Chemical properties of water

Water is an odourless, tasteless and colourless liquid. Each water molecule consists of two hydrogen atoms bonded to one oxygen atom (H2O). Each hydrogen atom has only one electron that is shared with oxygen which, in turn, takes part in the bond with one electron. Since electrons and protons are present in equal numbers, each water molecule is therefore neutral as a whole. Water molecules are said to be 'polar' because they have a weakly positive pole near oxygen and a weakly negative pole near hydrogen; in fact, oxygen is able to hold electrons closer to itself than hydrogen can, and the water molecule is thus negatively charged at the oxygen atom and positively charged at the hydrogen atom.

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The physical properties of water

Water has a high specific heat, i.e. it needs a lot of heat to heat up and takes long to lose the stored heat and get cold. This is why it is used in cooling systems (for instance in car radiators or to cool industrial equipment). And this is also why in coastal (or lake) regions the temperature of the air is milder: in these areas, as seasons change, the temperature of the water ‘mitigates’ the temperature of the air, since it decreases or increases more slowly than that of the air. Water has a high surface tension: that means that, once poured on a smooth surface, it tends to form spherical drops instead of expanding into a thin film.  

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Water cycle

In the oceans, water is in the liquid state. Solar heating causes a portion of surface water to evaporate and turn into steam, go up into the atmosphere and be carried by the wind. When a mass of water, that is already rich in water vapour, receives more water and saturates, or when it encounters a colder mass of air, water vapour condenses in the atmosphere, i.e. vapour turns into water again (or snow and ice, depending on how cold it is). This is how precipitations originate, through which liquid or solid water (rain, snow or hail) partly reaches the continents and partly gets straight back to the oceans.

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Hydrological cycle

The amounts of water that are moved through the hydrological cycle can also be estimated and evaluated in numerical terms. The tool we use is the global hydrogeological balance of the Earth. The total amount of water that evaporates from the surface of the oceans is more than the water that gets straight into them from precipitations. The difference is part of the amount of water that falls down on the continents. The total amount of water that falls on the continents actually consists of that which has evaporated, not only from the seas or oceans, but straight from the soil as well. 

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Drought and desertification

Due to the extent of damages and the number of people involved, drought is the number one natural catastrophe. A dry period is marked by less frequent precipitations compared to the annual average of the area. Drought is considered as serious when the average farming production decreases by 10% and catastrophic when it decreases by over 30%. Dry periods have become more frequent and more intense over the last few decades, involving almost all of the emerged areas.  

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What distinguishes the Earth from the other planets is the presence of the seas and oceans. Satellite pictures show the Earth as a “blue” planet, because two thirds of its surface are covered by huge masses of water. The whole of the earth’s environments where water is present in its liquid, solid or gaseous state is called hydrosphere. Most water can be found in the oceans, underground waters and in its solid state as ice in polar hemispheres. Water contained in the atmosphere as water vapour is instead just a very small part of the total amount.  

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Continental waters

Continental waters consist of water bodies like glaciers, rivers and lakes. Differently from seawaters, they are characterized by a low salinity and they move towards the sea because they are not too deep. See the different landscapes that we can encounter when we have a walk on the beach, on the mountains or on the hills. Glaciers form above the permanent snow line due to the accumulation of water at a solid state (snow that transforms into ice). The line varies according to the latitude on which continental glaciers (that uniformly cover wide areas) and mountain glaciers (that occupy mountain valleys) form… 

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The main characteristics of seawater are: salinity, melted gases, temperature, brightness. Salinity refers to the total salt content in 1000 grams of seawater and it has a value of around 35 grams. The percentage of the different substances that are present in the solution depends on the river contribution, on chemical reactions that occur in sea sediments, on volcanic activity and on the decomposition of organisms… 

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Sea currents

Huge masses of water displace for long distances due to the wind action. The direction of the movement is determined by the earth rotation (Coriolis force), which creates circular movements. In the Atlantic Ocean, regular and constant winds, the trade winds, move superficial water masses towards the Equator where they are diverted to the west by the Coriolis force (North-Equatorial current); when they reach the American continent they are pushed to the north and accumulate in the Gulf of Mexico.

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Water is vital and indispensable for humans and all living things. The importance of water for the human body is due to the fact that it makes up 60% of the body, a percentage that varies depending on age, body mass index and gender. Our heart and brain are about three quarters water while this proportion rises to 83% in our lungs. Even apparently 'dry' bones are made up of 31% H2O. Water in our bodies performs many functions, such as regulating temperature, lubricating joints and nourishing our brains. This is why, each day, every human being needs to drink enough water to maintain the water balance between inputs and outputs, avoiding dehydration which, when excessive, can even lead to death. In fact, we can go weeks without eating but survive only very few days without drinking. The minimum requirement of a human being to ensure survival is about 4.5 litres of water per day, taken either in liquid form (water or other drinks) or in food. However, for daily activities (such as, for example, personal hygiene and washing clothes) it is possible to consume more than 100 litres per day!

People are particularly interested in drinking water, which is becoming increasingly scarce in relation to the growing world population and due to pollution. In various parts of the world, installations that make seawater drinkable are in operation, especially along the coasts of arid regions, to make up for the lack of drinking water on the continents. The variability of climatic and hydrogeological conditions makes the availability of water vary considerably from one region to another. Even those countries with a high supply of fresh water run the risk of facing water scarcity. Lack of water, in fact, is a relative concept, as it can refer either to an absolute lack of water or to the difficulty of accessing safe water supplies. On all continents, water resources are being exploited to an increasing extent by the growing demand for irrigation for agricultural purposes, urbanisation and industrial use. Economic development and urban growth often cause damage to freshwater streams through increased pollution. This reduces the amount of good quality water available for primary uses such as drinking, feeding and personal hygiene.

During the last century, the world's consumption of fresh water has increased almost 10-fold, and about 70% of the water consumed on Earth is used for agricultural purposes. This is a decreasing percentage because consumption for industrial (22%) and domestic (8%) uses is increasing. In less developed regions, the percentage of water used for agriculture is higher, while in more developed regions the percentage of water used for industrial and domestic purposes is higher. The more we move towards low-income countries, the more the percentage devoted to crops increases to an average of 82%. High-income countries, on the other hand, allocate less water to agriculture (30% on average), but use more for industry and households, 59% and 11% on average.  

Drinking water in the world

The availability of drinking water varies according to geographical area, with significant differences between the North and the South of the world. The World Health Organisation (WHO) has estimated the personal daily requirement to be at least 50 litres, and ensuring availability and sustainable management of water and sanitation for all is Goal 6 of the 2030 Agenda for Sustainable Development. Unfortunately, treatment and management of fresh water requires huge investments and appropriate policies and, often, in territories where fresh water is 'scarce', the problem regards not only availability but also economic and political issues. 

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Water and agriculture

Agricultural use of water to irrigate fields represents the main form of consumption of global hydric resources and involves two thirds of global availability of fresh water. Water is not evenly distributed on our planet, hence, very often, human intervention is necessary to modify the natural flows of rivers and build artificial canals to bring water where it’s needed. Hydric requirements in agriculture depend on numerous factors among which are climate, soil characteristics, crop practices, irrigation methods, type of farming and many others. 

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Water employed for breeding

By 2025 more than 60% of the world population will live in water-stressed conditions. The zootechnical sector substantially contributes to water consumption and its pollution both directly and indirectly: 8% of world hydric consumption concerns the zootechnical sector that employs water mainly to irrigate fields farmed to produce fodder. Just think that 15 thousand litres of water are required to produce 1 k of beef! To produce 1 kg of chicken we need 3,500 litres of water whereas the production of cereals requires less water, that is 3,400 litres for rice, 2 thousand for soy, 1,400 for wheat. 

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Water and industrial activities

Man uses water also for industrial activities. The amount of water used in industrial activities depends on many factors, such as the kind of activity and technology used. Generally speaking, the uses you can make of water can be grouped into three types: for production (used as a raw material in the production process: for instance, the water required to make pasta or fruit juices), to cool machinery (basically, just like the radiator of our cars) and finally to wash equipment. 

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Water and energy

In addition, water is a renewable source of energy: the production of energy in hydroelectric plants does not involve real water consumption, but reduces the availability of water in other sectors (such as farming or civil sectors). Water is also used in thermoelectric plants, where it is not directly used to produce energy, but only to cool machinery. Water from industrial uses can also be polluted, even if now many industrialised countries have issued strict laws that limit the concentration of pollutants… 

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Water, sea and fish

Oceans are important not only for the plentiful food they can offer to man through fishing. From an ecological point of view, they provide over one half of the goods and services required to maintain the vital balance of the planet and host more animal species than any other system on Earth. In addition, through their volume and density, they absorb, store and carry large amounts of heat, water and nutritional substances. Fishing covers on average 25% of the world’s consumption of animal proteins. 

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Water is a vital resource for humankind and a precious commodity which must be safeguarded. According to the latest United Nations World Water Resources Development Report, the world could suffer from a 40 percent overall water scarcity in 2030. In fact, the availability of drinking water is gradually decreasing as a result of ongoing climate changes and global warming but also as a result of increased needs due to population growth and increasing consumption by industry and agriculture and as a result of its deterioration due to the negative impact of many human activities and our excessive use and waste of it.

It tends to be considered a renewable resource because, after being used, it returns to the water cycle entering seas, rivers and groundwater, but the quantity and quality of freshwater available on the planet is decreasing every year. From industry to agriculture, solutions are being sought to reduce consumption and prevent pollution through increasingly advanced purification systems.

Water saving in agriculture

Often a great part of water drawn for irrigation purposes doesn’t reach crops due to leaks along the pipes that transport water from the withdrawal point to the fields. Only part of the water reaching fields is used to grow crops, the rest is lost due to evapotranspiration and infiltration in the soil. Different strategies exist to save water in agriculture which, when integrated among them, can increase water saving.

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Industrial water saving

It is estimated that by 2050 the industrial sector will increase its water demand by 150%. Saving water not only means saving a precious resource at an environmental level but also entails a real costs saving. Besides specific technological measures for every type of industry, tactics as reuse and recycle can be put into practice. Reusing means using waste water after treating it, for example, municipal waste water which is treated for irrigation of green areas. 

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Give your contribution to water saving

There are many things we can do to save water and give our contribution to save and preserve water resources. Here are some suggestions. I drink tap water! Prefer tap water to bottled water. Tap water, infact, doesn’t need packaging. Drinking it means reducing the use of petrol to produce plastic bottles…

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Water Knowledge

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