Mixtures and water resources

  • Why is it important for humans, plants and animals to have access to clean water?
  • What is the difference between clean water and polluted water?
  • What are the different things that pollute water?
  • Why should wetlands be protected?

We have learnt that water can dissolve many substances - water is a good solvent. When water has unhealthy substances in it, we say the water is polluted. Polluted water is not clean.

Water pollution

When is water clean? We could say that clean water is free of pollutants.

What are pollutants? Pollutants are substances (or objects) that do not naturally belong in the water and are harmful to us and to the environment.

Pollutants may be any of the following:

  • Insoluble pollutants: these are things that do not dissolve in the water but make it dirty, such as oil, garbage and toilet waste (sewage).
  • Soluble pollutants: these are chemicals (eg. soaps, fertilisers) and poisons (eg. insecticides).
  • Living germs (bacteria) that can cause people or animals to get sick.

There is an interesting term in the video clip on Water Pollution: "natural pollutants". It is a nice topic for a short discussion. Even things that are quite natural can act as pollutants when released in large quantities. Human sewage is an extreme example. Most ecosystems are "buffered" against abnormal amounts of such substances, but only up to a certain point.

In the next activity we will discuss pollution and where it comes from.

Thinking about pollution


  1. We are going to discuss pollution.
  2. The following pictures of different polluted water sources, and the questions that follow, are meant to guide the discussion.
Pollution in a pond
A polluted river
Pollution on the coast
People have been using this stream to dump rubbish.
An oil spill


Look at the pictures above and make a list of all the objects that do not belong in the water.

Plastic bags, tyres, paper, polystyrene, bottles, shopping trolley, tins, metal rubbish bin, oil

What are the three main categories of pollutants found in water?

Insoluble pollutants

Soluble pollutants

Disease-causing bacteria (germs)

Which category of pollutants would you be able to see with the naked eye?

Insoluble pollutants

Which categories of pollutants would you not be able to see with the naked eye?

Soluble pollutants and germs

How do you think insoluble pollutants end up in water?

People allow garbage to fall into the water instead of placing it in a garbage bag for collection, and may even use the water as a toilet releasing germs into the water.

How do you think soluble pollutants end up in water?

There are many examples:

Rainwater can wash fertilisers and pesticides from farm lands into the rivers and other water sources.

People can allow their household water (that contain soap and detergents) to run directly into the rivers.

Industries can release polluted effluent into the rivers. (Effluent is the term for liquid waste or sewage discharged into a river or the sea.)

How do you think bacteria that cause illness like diarrhoea and cholera end up in water?

Bacteria get into the water mainly through people and animals using the water sources as a toilet. People and animals have bacteria that occur naturally in the digestive tract, but outside of this environment, they can be harmful.

How do you think oil ends up in the water, especially in oceans?

Cars drop oil and other chemical pollutants everywhere. These wash into the rainwater collection system and straight into rivers and seas. More dramatic disasters also pollute the ocean with oil. Oil may spill from a faulty oil rig in the ocean, or from a ship carrying oil which can leak or burst open.

What do all 3 categories of pollutants have in common?

Learners may say: 'They do not belong in clean water'. Help them to see that it is mainly through human activity that water sources become polluted.

Have you noticed that humans and their activities are often the reason why water becomes polluted?

As humans, we often forget that we are sharing this natural resource with many other organisms. Many of our activities can change the quality of the water in a way that affects the health and behaviour of other organisms.

So, as humans, we have a very important responsibility to look after our water resources.

Importance of wetlands

Nature has special methods of cleaning polluted water. In nature, water is purified in natural environments called wetlands. Wetlands are very efficient natural 'water treatment' facilities, and in this section we will learn how they work.

What are wetlands?

Some useful documents are available at these links and are free to use as long as you acknowledge them as the source. A suggestion is to get your school to print them in colour.

http://www.wetland.org.za/ckfinder/userfiles/files/2_1-%20MWP%20wetland%20basics%20presentation%201%281%29.pdf and http://www.wetland.org.za/ckfinder/userfiles/files/2_2-%20MWP%20wetland%20basics%20presentation%202.pdf

An area is a wetland if it has the following:

  • waterlogged soil,
  • water-loving plants and
  • a high water table.

If soil is waterlogged, it means that it is full of water. The water table refers to the level in the ground where all the soil below this level is waterlogged (full of water). If an area has a high water table, then this level is close to the surface. This means water will not filter down into the ground but remain on the surface forming a wetland.

Examples of wetlands are:

  • marshes
  • floodplains
  • swamps
  • lakes and pans
  • seeps and springs
  • estuaries
  • river banks

Look at the pictures of different wetlands.

Wetlands are not necessarily wet throughout the year.

  • Atemporary wetland is wet between 1 and 4 months of the year.
  • A seasonal wetland is wet during the rainy season. This means it will be wet between 5 and 11 months of the year, depending on the length of the rainy season.
  • A permanent wetland is wet throughout the year.

Why are wetlands so important?

Wetlands are very special places that should be protected. Why are they so important?

Three unique abilities of wetlands make them very important.

  1. Wetlands are like giant sponges:

Wetlands soak up water and store it. During a drought, when there is not much rain, this stored water can help to keep rivers and streams flowing so that animals and plants can stay alive.

  1. Wetlands slow down flood waters:

Water that is 'in flood' flows so strongly and quickly that it becomes dangerous. It can drown people and animals and it can cause damage to property and also to the environment, through soil erosion. Floodwater slows down when it flows into a wetland, because the wetland is a large area that can hold a large amount of water.

  1. Wetlands are natural filtration systems for purifying water:

As water flows through the wetland, it is filtered. Plants in the wetland trap soil particles and sediments, nutrients, as well as pollutants and disease-causing organisms which make the water unsafe.

With regards to the pollutants being filtered from wetlands, it is only certain kinds, and only in certain loads. Insoluble wastes such as plastics should not end up in a wetland. Bacteria and other germs are neutralized. Chemical pollutants such as heavy metals are trapped, but if they become concentrated in too large amounts, they need to be taken out by removing plant matter that has absorbed them.

Making a model of a wetland

Teacher note: The reason for doing this activity is to help learners understand how different surfaces, especially those covered in plants, allow water to drain at different rates allowing soil to retain much of the water, and other surfaces to lose a lot of water. This will also show how wetlands help to slow down water and filter it.


  • grass moss or other garden moss
  • bricks
  • sand
  • soil
  • shallow plastic trays (about 7-10 cm deep)
  • hardboard
  • watering can
  • measuring tool to measure 2 litres of water
  • hand or electric drill (to be used only under STRICT ADULT SUPERVISION)
  • watch or stopwatch
  • plastic window box

The watering can must be the kind with a 'shower-type head' at the front that will simulate rain falling


  1. Drill a hole in the middle and at the bottom of one side of the plastic box.
  2. Pack 2 layers of bricks, the window box, and the hardboard as shown in the illustration.
  3. Position the hole you drilled in the tray over the centre of the hardboard so you do not accidentally lose water over the sides that should run into the window box.
  4. Fill your watering can with 2 litres of water.
Setup for the drainage experiment
  1. Moss is found in many wetland areas like marshes, bogs and waterways. Place the moss inside the tray over moist soil. Pour the 2 litres of water slowly and evenly over the moss. Time how long it takes for the water to filter through the moss and run into the window box.
    1. How long did it take the water to run into the window box?

    2. Why do you think it took the water this long to drain off?

Moss holds water very well and that is why it took so long for the water to drain off.

Perhaps someone should remain timing that experiment while the rest move on to the others.

  1. Repeat this experiment with sand - this is what happens to rainwater in the Namib or Sahara Deserts.
    1. How long did it take the water to run into the window box?

    2. Why do you think it took the water this long to drain off?

Sand does not hold water very well at all. That is why the water drained off so quickly.


What did you learn from doing this experiment about the relationship between plants and water drainage in a wetland?

Learner-dependent answer.

Wetlands are also important as they provide a habitat to many different plant and animal species. Wetlands are important because of their biodiversity.

Ask the learners why biodiversity is important. This is a link back to what they did in Life and Living.

Do you remember studying habitats in Gr. 4 and Gr. 5? What does a habitat provide to an organism?

A habitat provides food, water, shelter, a place to raise young, a place to hide from predators.

Discuss with your partner what you understand by the term 'biodiversity' and write it down below

Biodiversity refers to the variety of organisms (plants and animals) in a specific area. An area with a high biodiversity will have many different species of plants and animals.

Let's now do some research about the wetlands in South Africa and their importance.

Before doing the following activity, it is recommended that you show this Powerpoint presentation to the learners:


If this is not possible, the presentation could be given to the learners in printed format.

Researching the different wetlands in South Africa


  • pamphlets, posters and any other reading material on wetlands
  • books or other reading material from home, or printed pages from the internet
  • poster material: cardboard, glue, colour pencils, scissors, pictures, etc

Arrange a visit to a nature reserve to study a wetland area firsthand. Or invite a speaker from a nature conservation site (such as SANParks) to talk to your class about wetlands. BEFORE the visit: tell learners to read through the information brought to school and some of the books and reading material in your class. From this information, set at least 5 questions that you could ask the Nature Conservation Officer when s/he comes to visit your class, or when you go on the outing to the nature reserve. At least 2 of these questions should focus on the dangers to wetlands.DURING the visit: Tell learners to REMEMBER to take many notes while listening to the Nature Conservation Officer.AFTER the visit: In their groups, learners must make a poster about wetlands, using the questions to guide them. NB. If you do not manage to visit a wetland, learners must still complete the research task by reading up on the internet and in books to answer the questions and present a poster.


  1. You might get to visit a wetland near your school or hear a talk by a conservationist.
  2. If you do not get this opportunity, you must still complete the project by doing research in books, pamphlets and on the internet and answer the questions below.
  3. Present your report as a poster.


  • What is a wetland?
  • What does a wetland do for the environment?
  • What does a wetland do for plants and animals?
  • What does a wetland provide for humans?
  • What are the environmental dangers that wetlands face?
  • Choose a specific wetland and assess the habitats, biodiversity and water quality of this wetland.
  • What would the impact be to biodiversity and water quality if this wetland was lost?

Wetlands should be protected because:

  • they are natural water-purification systems;
  • they act like sponges to store water in the wet season and supply water in the dry season; and
  • they slow down flood water to prevent damage to property and the environment.
  • Clean water is vitally important to ensure the health of humans, animals and plants.
  • Water can be polluted by insoluble substances, soluble substances and disease-causing germs.
  • Wetlands act as natural water purifiers because they can absorb soluble and insoluble impurities from water and they regulate water flow across the landscape.

  1. Look at the picture below of the bird covered in oil and answer the questions.
A bird covered in oil. http://www.flickr.com/photos/19378856@N04/2037098785/

How do you think the oil got into the water that this bird lives in?

An oil spill from a ship or oil rig

Is oil a soluble or insoluble water pollutant?

Oil is insoluble as it floats on top of the water.

How will the oil damage this bird and other sea animals?

The oil coats their feathers or skin making it hard for them to fly. It is very sticky and very difficult to remove. The oil can get into their lungs and stomachs which will kill them. Oil also kills fish (possibly the bird's food source) because it prevents oxygen from the air dissolving in the water (oxygen is insoluble in oil).

List some of the dangers that wetlands face.

Learners could list any of the following:

  • drainage of wetlands for pastures and crops
  • overgrazing that leads to soil erosion
  • incorrect burning that leads to soil erosion
  • timber production
  • incorrect siting of dams
  • pollution
  • mining activities in wetlands
  • urban development

All the above human activities can affect the water flow and water quality of the wetland and this can ultimately destroy the wetland.

Search the wordsearch puzzle for the types of animals found in wetlands.

See if you can find:

  • clam
  • crayfish
  • mosquito
  • heron
  • frog
  • egret
  • dragonfly
  • turtle
  • fish
  • shrimp
  • crab
  • salamander
  • duck