What is fresh water? And why isn’t it salty?

Fresh water is water that contains low amounts of salt. Fresh water has a salt level (‘salinity’) of 0.05% or less. That makes fresh water a lot less salty than the salt water you’d find in the ocean, which has an average salinity of 3.5%.

Over 40% of the world’s fish species are freshwater fish.

Where is fresh water found?

There are 3 main types of fresh water biomes:

  1. Ponds & lakes
  2. Streams & rivers
  3. Wetlands

Usually, fresh water is found in low altitude areas. This is because bodies of fresh water are created by rainfall or snowfall and this water collects in low-lying areas.

Why is fresh water not salty?

When water evaporates from the ocean, it leaves the salt behind. The water then falls to the ground in the form of rain, which forms lakes and rivers. These lakes and rivers aren’t salty, because the rainwater didn’t contain salt.

However, as the rivers flow towards the ocean, the water picks up salt from the soil and rocks. This salt is carried along in the river until it reaches the ocean, where the salt is distributed in the ocean water.

Oceans are therefore salty because they are the dumping ground that accumulates all of the salt. Whereas rivers and lakes are continually refreshed with salt-free rain water.

Why is fresh water important?

Around 40% of all fish species live in fresh water, even though fresh water makes up just 3% of the water on Earth (the rest is saltwater). This means fresh water is very important, as over 10,000 freshwater fish species depend on it to survive.

Of course, fresh water is also important to land animals, which drink fresh water from lakes, rivers and streams.

Is fresh water found in the ocean?

The ocean is saltwater, not fresh water. However, interestingly, there are bodies of freshwater buried underneath the ocean floor!

What is the largest fresh water body in the world?

Measured by volume, the largest fresh water body in the world is Lake Baikal in Russia. It is the deepest lake in the world and contains around 20% of all the fresh water on Earth.

Fresh water Lake Baikal
Lake Baikal, in Russia, holds the largest volume of fresh water anywhere on Earth. iStock.com/demerzel21

Where does our fresh water come from?

Most of the fresh water we drink comes from surface water. This is water that has fallen as rain or snow to form lakes and rivers. We take the water from the lake or river and send it to a treatment center to make it safe to drink.

The other place that our fresh water comes from is ground water. This is water that has fallen as rain or snow and then soaked into the ground. The water is then trapped in aquifers, which are underground layers of porous rock or materials such as sand or gravel.

Can you drink fresh water?

Humans can only drink fresh water and we need it to survive. If you drank saltwater instead of fresh water then you would quite quickly die of dehydration.

However, this doesn’t mean that it’s ok to drink fresh water directly from a lake or river. The water we drink has been processed at treatment centres to remove chemicals, bacteria and parasites that can make us sick. If you drink directly from a body of fresh water – even if it looks clean and crystal clear – you may be consuming some things that could make you very ill or even kill you.

Drinking directly from a natural fresh water source should only be done as a last resort. Wherever possible, drink properly processed water from your drinking water supply.

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