Definition: Water around the world

Water around the world – key figures – water in all its forms:

On our planet, water exists in various forms:

- glaciers and snow,

- lakes and bodies of water,

- rivers and streams, which are fed by rainwater running off the land,

- wetlands (bogs, marshes and wet heaths),

- groundwater, which is fed by rainwater and river water infiltration,

- oceans and seas, composed of salt water,

- clouds,

- water vapour in the atmosphere.

Water is almost as old as our planet: it appeared 3 or 4 billion years ago. Since then, its volume has remained stable overall. It is always the same water that circulates and is constantly transformed through the water cycle.

Water cycle

Water is everywhere around us and is one of the fundamental elements of our planet. All this water is constantly transforming and circulating in the atmosphere, on the surface and underground. This is the water cycle.

Water covers 72% of the 509 million km² of the Earth's surface. Its volume is estimated at around 1.4 billion billion litres of water!

This volume of water is stable.

The water on the blue planet is distributed as follows:

97.20%: salt water

2.15%: polar ice

0.63%: groundwater

0.019%: surface water (lakes, rivers and streams)

0.001%: water in the atmosphere.

Only 0.65% of this water is neither salty nor frozen, and therefore potentially drinkable by humans.

Humans are demanding creatures; they only drink and use fresh water, i.e. water that is not salty.

All land animals and plants need fresh water to live.

Water appeared at the same time as the formation of the Earth and was formed in the universe. Today, thanks to the atmosphere, which acts as a giant lid over the Earth, it cannot escape from our planet (i.e. beyond the clouds, it does not leave the universe). It is always the same water that completes the water cycle. Water is used by humans, animals and plants, but it always returns to nature.

For example, water used to water the garden returns to the earth and into the groundwater, and the water that humans drink "comes out" of their bodies through perspiration and urine. Unfortunately, our urine, garden fertiliser, etc. will damage (pollute) this water before it returns to nature.

Water is a gift from nature; it is not "manufactured" on earth.

79% of precipitation falls on oceans, 2% on lakes and only 19% on land.

From the earth to the sky

97.2% of the water on the planet is found in the form of salt in the seas and oceans. Molecules on the surface capture solar energy, evaporate and return to the atmosphere in the form of vapour. This continuous evaporation from the oceans, under the effect of the sun, is the primary source of fresh water. To this must be added evaporation from rivers and lakes, as well as from plants.

Condensation is the process by which vapour rises, cools and condenses into particles, thus changing to a liquid (droplets) or solid (ice crystals) state. These particles, driven by the wind, then gather together to form clouds.

The Pacific Ocean accounts for almost half (45.9%) of the world's oceans. It also holds the record for depth: more than 11,000 metres in the Mariana Trench (by comparison, the Himalayas are 8,846 metres high at Everest, and the Alps are 4,807 metres high at Mont Blanc).

Water renews itself if given enough time: 1,000 years for groundwater, 4,000 years for an ocean, and 15,000 years for a glacier!

- Salt water accounts for 97.2% of the planet's water. Most of the 2.5% of fresh water is locked up in glaciers.

Water use

- Agriculture is by far the largest user of water, accounting for 70% of total consumption. Unless there is a significant improvement in irrigation systems, this share could rise to 90%.

- Industrial uses account for 20% of total consumption, compared with 10% for domestic uses.

Three physical states of water, but in various forms

Water in its liquid, solid or gaseous state is everywhere around us and is one of the fundamental elements of our planet.

Liquid state

rain: water droplets from clouds,

Clouds: formed by the accumulation of tiny water droplets high in the atmosphere.

fog: water droplets suspended in the air,

not forgetting, of course, the water in rivers and the sea.

Solid state Snow:

consisting of tiny star-shaped ice crystals. Snowflakes are formed by the accumulation of crystals,

frost: formed by the freezing of fog,

ice: results from the freezing of water that has fallen to the ground or into rivers,

glaciers: these are caused by the accumulation of snow in high mountains, which settles under its own weight.

Gaseous state

water vapour: this is a gas that becomes visible when it condenses.

Water around the world

It is estimated that more than 80 countries around the world (representing more than 40% of the global population) experience serious water shortages.

Inequalities

A country's water poverty can have several causes. Sometimes water resources are insufficient for the number of inhabitants. On the other hand, the absence and irregularity of rainfall can also give rise to deserts in arid areas.

Today, it is estimated that more than 1.7 billion people worldwide do not have access to drinking water, while more than 1.3 billion are deprived of adequate sanitation facilities (overpopulation, pollution, poor water supply and lack of money may be the causes).

Water as a source of conflict

The sharing of water is at the root of certain conflicts around the world, either between different users within the same country or between different countries sharing the same resource.

The solution to these global inequalities often lies in cooperation between countries, with the richest showing solidarity with the poorest.

Ecological balance and pollution issues must be addressed on a global scale. Certain international organisations, such as UNESCO (United Nations Educational, Scientific and Cultural Organisation) and WHO (World Health Organisation), as well as various associations, are already working towards this goal.

The future of the blue planet will necessarily require global awareness: water does not belong to any particular country, it is the heritage of all.

Growth in demand

- With the world's population growing by around 80 million people per year, demand for fresh water is expected to increase by 64 billion cubic metres per year by 2050.

- 90% of the 3 billion people who will be added to the world's population by 2050 will be in developing countries where, today, the population does not have adequate access to drinking water and sanitation.

- Groundwater extraction increased fivefold in the 20th century.

Water-related diseases

- By 2030, more than 5 billion people will still not have access to adequate sanitation.

- Three million people die prematurely each year from water-related diseases in developing countries.

Climate change

- By 2030, 47% of the world's population will live in areas subject to significant water stress.

- In Africa, by 2020, 75 to 250 million people could be exposed to increased water stress due to climate change.

Feature

UNESCO Courier published a detailed study in its 3rd issue of 2009 entitled "Our beloved water, mistreated", which we recommend. Editorial by Agnès Bardon (UNESCO) - Water between the field and the fork by Jens Lubbadeh, journalist at Spiegel, Germany - The Blue Scorpions strike by Linda Nordling, Swedish journalist living in South Africa - The Yangtze or a journey through time, interview by Katerina Markelova (UNESCO Courier) - Water management: Australia turns the page by Åsa Wahlquist, Australian journalist - Water in a changing world by DR Olcay Ünver, coordinator of the World Water Assessment Programme, answering questions from Cathy Nolan (UNESCO).