In many parts of our country we are experiencing a huge drought - we do not always realize how important water is to us until we do not have it.
- Can you think of reasons why water is important to humans, plants and animals?
How long a person can survive without water. A human can go for more than three weeks without food (Mahatma Gandhi survived 21 days of complete starvation), but water is a different story. At least 60 per cent of the adult body is made of it, and every living cell in the body needs it to keep functioning
It is very important that we save water and not waste it. We cannot just think 'It will rain again', because it can be a long time before the rain comes and the dams will eventually run dry.
There are many ways in which we can do our small part to save water.
But where do we get our water from and how does it rain?
Water keeps on going in a circle - from the Earth (see, dams and rivers) into the air, it forms clouds and the rain comes down and then the circle starts again - this is called the 'water cycle' or 'hydrologic cycle'.
The hydrologic cycle begins with the evaporation of water from the surface of the ocean. As moist air is lifted, it cools and water vapor condenses to form clouds. Moisture is transported around the globe until it returns to the surface as precipitation.
Each part of the cycle goes through a specific process
- The liquid water from the rivers and dams and the sea turns into a gas because the sun is shining on it and heating it up - this is called 'evaporation'.
- The gas goes up into the air and in turns back in to a liquid (small water droplets) and this is called 'condensation'.
- The droplets form clouds and when the cloud gets too heavy it starts raining, snowing or hailing, which is called 'precipitation'.
- Now the water falls down to earth and runs down the hills into the rivers, dams and the sea or go into the ground.
- Make sure you can explain this cycle in your own words as well as using the words in bold in your explanation.
Most of earth's water is stored in the ocean, rivers, ice caps, in the ground or the atmosphere. These are all called 'water bodies'.
- Have a look at the video and answer the questions that follow
- How much of earth is covered by oceans?
- Why is the water from an ocean not safe to drink?
- Which ocean is the largest?
- What is the difference between an ocean and a sea?
- Name a few oceans on Earth.
- Where does a river start and what is it called?
- Where does a river end and what is it called?
- Which river is the longest on earth?
- What is a lake?
- Why do lakes need a continuous source of new water?
You will build a model that shows the water cycle (or make a poster of it) and you can do an experiment to show how evaporation and condensation takes place. Watch the video if you would like to do the experiment.