Why is water so vital? Facts about water that will surprise you
Water is vital because every form of life depends on it, the human body is up to 60% water and there is no economy without it. And it is scarcer than it looks: only 2.5% of Earth's water is fresh, and almost 70% of that is frozen. See 10 facts about water that will surprise you, what they mean for Brazil and the role of companies.
By T&D Sustentável 7 min read
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Water is vital because no known form of life exists without it: it makes up as much as 60% of an adult’s body, regulates the climate, sustains ecosystems and drives the production of food, energy and goods. And it is scarcer than it looks. According to the United States Geological Survey (USGS), only 2.5% of Earth’s water is fresh, and 68.7% of that fresh water is locked in glaciers and ice caps.
In short:
- More than 96% of Earth’s water is salty; only 2.5% is fresh, and most of it is frozen or underground.
- Lakes and rivers add up to less than 0.01% of all the water on the planet.
- An adult’s body is up to 60% water; the lungs, about 83%.
- Brazil has about 12% of the planet’s surface water availability, but almost 80% of it is in the Amazon basin.
- Even so, 2.1 billion people worldwide lack safely managed drinking water.
Why is water so important for life?
Because it takes part in almost everything a living being does. Water carries nutrients and waste, regulates temperature, is the medium in which cells’ chemical reactions happen and gives shape to tissues. In ecosystems, it sustains rivers, forests, wetlands and marine life and regulates the climate. In the economy, it irrigates crops, cools industries and thermal plants, generates energy in hydropower plants and supplies cities.
This dependence is why Brazil’s Water Law, Law No. 9,433/1997, treats water as a public good and a limited natural resource with economic value.
What are the facts about water that will surprise you?
Ten, all with a source:
- Almost all of Earth’s water is salty. More than 96% is in oceans, seas and bays, and only 2.5% is fresh (USGS).
- Most fresh water is frozen. Glaciers, ice caps and permanent snow hold 68.7% of the planet’s fresh water, and the ground, 30.1% (USGS).
- Rivers are a tiny fraction. Surface fresh water is a little over 1.2% of fresh water, and rivers hold only 0.49% of that share. Together with lakes, they come to less than 0.01% of all water on Earth (USGS).
- You are, in large part, water. Up to 60% of an adult’s body is water; the brain and heart are 73%, the lungs about 83%, and even bones are 31% (USGS).
- An adult man needs about 3 litres of water a day, according to the USGS.
- Brazil is a water superpower. Brazilian rivers hold about 12% of the planet’s surface water availability, according to Brazil’s National Water and Sanitation Agency (ANA).
- But the water is far from those who use it. Of the roughly 250,000 mÂł/s that flow through the country, almost 80% are in the Amazon basin (ANA, 2025). Rainfall ranges from less than 500 mm a year in the semi-arid Northeast to more than 3,000 mm in the Amazon.
- Food hides a lot of water. A kilo of beef takes, on global average, 15,400 litres of water along the chain, and a kilo of irrigated rice in Brazil about 1,050 litres in irrigation alone. See virtual water and water footprint.
- Almost 40% of treated water is lost on the way. In 2024, Brazil lost 39.53% of its treated water before it reached the consumer, according to Instituto Trata Brasil. See water losses in Brazil.
- 1 in 4 people in the world still lacks safe drinking water. That is 2.1 billion people, according to WHO and UNICEF, in a 2025 report.
How much water does the human body contain?
Up to 60% of an adult’s weight, according to the USGS, with variation between organs:
| Part of the body | Water |
|---|---|
| Lungs | about 83% |
| Muscles and kidneys | 79% |
| Brain and heart | 73% |
| Skin | 64% |
| Bones | 31% |
That is why dehydration affects energy, concentration and the body’s functioning so quickly, and why the quality of the water you drink matters as much as the quantity.
Why is water scarce if the planet is blue?
Because almost all of it is salty, frozen or underground, and the accessible part is badly distributed. This is how the USGS divides Earth’s water:
| Where it is | Share |
|---|---|
| Oceans, seas and bays | 96.54% of all water |
| Fresh water | 2.5% of all water |
| Glaciers, ice caps and permanent snow | 68.7% of fresh water |
| Fresh groundwater | 30.1% of fresh water |
| Surface and other fresh water | a little over 1.2% of fresh water |
In Brazil, abundance coexists with scarcity. The Amazon basin holds almost 80% of the water flowing through the country, while the Southeast accounts for 34.5% of withdrawals, according to ANA. The semi-arid region gets less than 500 mm of rain a year. And the crises of 2014, in São Paulo, and 2021, at the hydropower plants of the Paraná basin, showed that even the richest regions can run out of water, as told in water crisis in Brazil: 2014 and 2021.
Why does water matter to companies?
It is an input, a cost and a risk at the same time. In 2024, manufacturing accounted for about 10% of the water withdrawn in Brazil, and city supply, which serves offices, shops, hotels, hospitals and schools, about 22%, according to ANA. Each sector’s figures are in water use by sector.
For a company, the importance of water shows up on three fronts:
- Operations. Without water, kitchens, toilets, air conditioning, cleaning and processes stop.
- Cost. The water and sewage bill, the energy spent pumping and heating and, for those who abstract directly, the water use charge.
- Risk. In a water crisis come contingency tariffs, low network pressure and restrictions on abstraction, as shown in water crisis and companies.
How can a company protect water?
By measuring, cutting waste and using each litre more than once. In practice: knowing consumption by area and by hour, fixing invisible leaks, installing efficiency technology at points of use, reusing water where quality allows and tracking the results every month. The full roadmap is in water savings in companies.
T&D’s SEA 360º handles implementation, without building works, with a baseline under the IPMVP protocol, efficiency technology at points of use, electronic leak detection and repairs, and continues with ongoing management, with monthly efficiency and ESG impact reports. The ceiling observed in the full programme is a 70% reduction in consumption.
Frequently asked questions
Why is water important for living beings?
Because no known form of life exists without it. Water carries nutrients and waste, regulates temperature, is the medium for cells’ chemical reactions and makes up much of the body’s tissue: up to 60% of an adult’s body is water.
How much of the planet’s water is fresh?
Only 2.5%, according to the USGS. Of that fresh water, 68.7% is in glaciers, ice caps and permanent snow, 30.1% is underground and a little over 1.2% is on the surface and elsewhere, such as ground ice, lakes, soil moisture, the atmosphere, wetlands and rivers.
How much water is in the human body?
Up to 60% of an adult’s body is water, according to the USGS. The lungs are about 83% water, muscles and kidneys 79%, the brain and heart 73%, skin 64% and bones 31%.
Does Brazil have a lot of water?
It does: about 12% of the planet’s surface water availability, according to ANA. But almost 80% of the water flowing through the country is in the Amazon basin, far from most of the population and industry, and regions such as the semi-arid Northeast get less than 500 mm of rain a year.
Why does water matter to companies?
Water is a production input, a cost item and a source of risk. Without it, operations stop; the water bill, pumping energy and water use charges weigh on costs; and water crises bring surcharges and restrictions on use.
Sources
- USGS, Where is Earth’s water?: distribution of salty, fresh, frozen, underground and surface water
- USGS, The water in you: water and the human body: water in the human body and daily needs
- ANA, presentation on the state of water resources in Brazil at the ECLAC seminar, November 2014, in Portuguese: Brazil’s surface water availability compared with the planet
- ANA, Conjuntura dos Recursos HĂdricos no Brasil 2025, Water quantity and Water uses chapters, in Portuguese: flows, rainfall and withdrawals by sector and region
- WHO, “1 in 4 people globally still lack access to safe drinking water”, with UNICEF, 26/08/2025
- Law No. 9,433 of 8 January 1997, Article 1, in Portuguese: water as a public good and a limited resource with economic value
- T&D SEA 360Âş
