Water and Our Living Environment

Water and ecosystems

An ecosystem is a group of living things and the place they live in, all linked together. Water is part of every ecosystem. A pond, a river, a wetland, a forest and a desert all have water in some form, even if only a little.

• Living things are mostly water. Plants and animals need it inside their bodies to live.
• Water is a home. Fish, frogs, insects and water plants live in it.
• Water moves things. Rivers carry food, soil and seeds from one place to another.
• Water changes the weather. It evaporates, forms clouds and falls as rain.

If the water in a place goes down or becomes dirty, many kinds of living things are hurt, and the ones that eat them are hurt too. That chain is why we say water keeps an ecosystem healthy.

History of water and humans

Early people stayed near rivers and lakes, because water was needed every day. The story of how we got water has four easy stages:

1. River and spring. People walked to the water and carried it home.
2. Wells and tanks. People dug down to reach underground water and made ponds to store rain.
3. Canals and pipes. People moved water over long distances to fields and towns.
4. Taps and treatment. Modern towns clean the water and send it through pipes to every home.

Each step brought water closer, so more people could live in one place. It also meant we used more water and had to protect the source.

Water as a resource

A resource is something we use. Water is used for drinking, cooking, washing, growing food, making things in factories and making electricity.

Look at the 100 cubes in the 3D. About 97 cubes are in the oceans and are salty. About 2 are ice in glaciers and ice caps. About 1 is liquid fresh water, mostly underground. Rivers and lakes together are much less than even one-tenth of a cube. So the water that is easy for people to use is very small.

The amount of water on Earth does not run out, because the water cycle keeps moving it. But clean fresh water in the right place at the right time can run short. Some places get lots of rain and some are dry, and a growing number of people share the same supply.

These numbers are rounded. Different books give slightly different values, but the big picture is the same.

Efficient use and water quality conservation

Efficient use means getting the same job done with less water.

• Fix leaks: a tap that drips all day wastes litres.
• Take shorter showers and turn the tap off while brushing.
• Reuse water, for example use the water from washing vegetables on plants.
• On farms, give plants water only where roots are and only when needed.

Water quality conservation means keeping water clean in the first place.

• Do not throw rubbish, oil or chemicals in drains, rivers or ponds.
• Treat sewage before it goes back to a river.
• Use fertiliser and pesticide carefully so rain does not wash them into water.
• Keep trees and plants near rivers, because roots hold soil and catch dirt.

Cleaning water costs energy and money, so stopping pollution is cheaper than fixing it later.

Try it: count your buckets

At home, put a 10-litre bucket under the tap or shower and count how many buckets you fill for one shower or one wash. Write it down. Then try the habit changes from the 3D (shorter shower, no leaks) for three days and count again. Did you save a bucket? Predict first, then check.

Key formulas and definitions

• Water on Earth ≈ 97% salt + 2% ice + 1% liquid fresh (rounded)
• Daily use of a group = people × litres per person
• Buckets = litres ÷ 10
• Days a store lasts = store (L) ÷ daily use (L)
• Key terms: ecosystem, resource, fresh water, efficient use, water quality

Worked examples

Common mistakes

• Thinking Earth has lots of water we can drink. Most of it is salty or frozen.
• Thinking water is used up. It moves through the water cycle, but clean water in the right place can run short.
• Believing a small drip does not matter. Many drips over a day add up to litres.
• Forgetting that dirty water harms living things in a pond as well as people.