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What's in your school drainage system?

About this lesson

Students study natural and processed items that enter and pollute the school drainage system.

Year level: 4, 5

Theme: Stormwater and waterways

Learning objectives

Students can:
  • explain the difference between wastewater and stormwater
  • predict items to be found, and the relationship between rainfall and pollutants
  • undertake a study of pollution entering the drainage system
  • understand natural and processed items and their impact on the environment.

Curriculum links


  • Natural and processed materials have a range of physical properties; these properties can influence their use ACSSU074
  • Science knowledge helps people to understand the effect of their actions ACSHE062
  • Science involves making predictions and describing patterns and relationships ACSHE061
  • Scientific knowledge is used to inform personal and community decisions ACSHE217
  • Things you will need

    Lesson description

    This lesson is best run when rain is expected.


    • Explain the difference between stormwater and wastewater
    • Ask students the following questions: Where does stormwater end up? What types of objects and materials can get into drainage systems? What problems do they cause?
    • Watch the video Healthy waterways plastic pollution revolution (3:15).   


    • Discuss the types of items students would expect to see at the entrance to a drainage system.
    • As a class, discuss the questions on the Drainage systems study activity sheet and have students complete their predictions about what will be found, and the relationship between rainfall and pollutants.
    • Divide students into groups and allocate them a part of the school drainage system to monitor for the week.
    • Students monitor the rainfall on Drainage system collection activity sheet.
    • Students separate items into natural and artificial/processed and record these and the quantity on the activity sheet.
    • Using gloves or litter pickers students collect the items at the entrance to drainage systems, place them in a plastic bag and put them in a rubbish bin.
    • Students answer the questions on the Drainage system collection activity sheet.

    Reflect & summarise

    • At the end of the week discuss the items that were found. Which were the most unusual? Which were the most common? Which were the least common? Results can be made into a chart.
    • Discuss whether the natural items found are a form of pollution? (Yes, they are nutrient rich and can promote algal blooms).
    • Focus on the artificial or processed items identified and discuss their potential impact on the environment.
    • What can be done to educate the school and the general community about what should not enter drainage systems?

    Extension activities

    • Investigate where the school's drainage system leads too. Invite Sercul to run a 'Clean Drains River Gains' incursion.
    • Example the 4 Rs: Refuse, Reduce, Reuse, Recycle and use the school newsletter to reduce the community's use of plastic.

    Teacher background information

    What is wastewater?

    Wastewater is a hidden part of everyday life and is collected from households, commercial businesses and industries. It is directed by sewers to treatment plants and treated to an environmentally acceptable standard.

    The treated wastewater is then either:

    • returned to the marine environment via ocean outfalls
    • reused in horticulture or to irrigate recreational areas
    • allowed to infiltrate back into the ground or evaporate.

    In WA, Water Corporation is responsible for the treatment and disposal of wastewater. It operates more than 100 wastewater treatment facilities around the State.

    Drainage systems

    Drainage systems consist of pipes or open-channel drains that convey storm water runoff and groundwater to natural water bodies such as rivers, wetlands, and the ocean or to compensating basins. They often follow the route of natural watercourses that existed before any land development or clearing took place.

    Drainage systems prevent flooding of developed land from surface runoff and from rising groundwater levels. In areas or high water tables, drainage systems lower the groundwater level so that land can be developed.

    Storm water

    Storm water is not treated and in some cases leads directly to our water bodies such as rivers, lakes, wetlands or the ocean. Alternatively, the water seeps back into the ground and is taken up by plants, evaporates or gradually trickles down into the groundwater. Storm water runoff easily collects pollutants along its path.

    Impact of littering

    Litter is a serious pollution issue that affects our waterways, coastline and ocean impacting on wildlife, human health and the marine environment. In 2015 it was estimated that 8 billion tonnes of litter and waste debris enters the world’s oceans annually and most of this comes from the land. Plastics create up to 99% of this debris. Rivers, streams and storm water drains transport litter hundreds of kilometres to the ocean where currents and wind carry them all over the world.

    Nutrients can be pollutants

    Nutrients are elements or compounds including nitrogen, phosphorus and organic carbon. They enter the rivers from the catchments through drains, surface runoff and groundwater. The most common sources of nutrients entering our rivers include fertilisers, plant matter (e.g. grass clippings, leaves), detergents, sewage and animal waste.

    Nutrients are essential for plant growth, including algae. However excess nutrients fuel algal blooms and can promote harmful algae, which take oxygen out of water. Low oxygen conditions and toxic algal blooms can result in fish deaths.


    Related lessons

    Where does storm water go at school?

    How pollution affects our catchment

    Did you know?

    Plastic pollution affects every waterway, sea and ocean in the world. Disposable plastics are the greatest source of plastic pollution and include plastic bags, straws and bottles.

    Key vocabulary

    • Catchment: The surface area from which runoff flows, sometimes via drainage systems, to a river, dam or wetland.
    • Compensating basin: A sandy basin where storm water is temporarily stored and re-enters the groundwater system.
    • Drainage system: A system of drains.
    • Groundwater: Water that is held underneath in the rock or soil.
    • Stormwater: Surface water caused by rain.
    • Wastewater: Water that has been used inside a home, business or industry that travels to a wastewater treatment plant.