Keep Water Clean

Why it matters

A clean river sparkles with life. But dump waste into it and the fish start to die. Some of our actions harm water, and some help keep it clean.

Predict first

Which of these makes water DIRTY and unsafe?

Untreated sewage pours germs and waste into water and pollutes it badly. Planting trees, fixing leaks and using gentle soaps all help protect water instead.

• Planting trees along the river bank
• Letting untreated sewage flow into the river — correct
• Fixing a leaking tap at home
• Using biodegradable soap

What you do

Sort each action into whether it pollutes water or protects it.

Check yourself

When fertiliser washes off farms into a lake, tiny plants and algae grow wildly and the water loses its oxygen. What is this harmful process called?

Fertiliser run-off feeds algae, which grow out of control. When they die and rot, the water runs out of oxygen. This is eutrophication, and it kills fish.

Why does farm fertiliser washing into a lake end up killing the fish?

Fertiliser causes algae to bloom. As the algae die and decay, they use up the oxygen dissolved in the water, so the fish cannot breathe and die.

To keep our drinking water safe, what should we avoid doing near a source of drinking water?

We should not bathe or wash near drinking-water sources, because soap, dirt and germs from washing pollute the water and make it unsafe to drink.

• Eutrophication — correct
• Desalination
• Sedimentation
• Chlorination
• It causes so much algae to grow that the water runs out of oxygen for the fish — correct
• The fertiliser feeds the fish so well they burst
• It turns the water into salt water
• It makes the water too cold
• Bathing or washing clothes in it — correct
• Looking at it from a distance
• Planting trees beside it
• Building a fence around it