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Nutrients in our waterways – how much is too much?

About this lesson

Students investigate the effect of nutrients in our waterways and demonstrate their understanding through a written or visual project.

Year level: 7

Theme: Stormwater and waterways

Learning objectives

Students can:
  • discuss pollution and the effect it has on water in the environment    
  • understand what nutrients are and how we can reduce them reaching our waterways
  • plan, draft and produce a project, exhibit or performance to demonstrate their understanding of nutrients and their effect on waterways.

Curriculum links


  • Some of the Earth's resources are renewable, including water that cycles through the environment, but others are non-renewable ACSSU116
  • Science understanding influences the development of practices in areas of human activity such as industry, agriculture and marine and terrestrial resource management ACSHE121


  • Plan, draft and publish imaginative, informative and persuasive texts selecting aspects of subject matter and particular language, visual, and audio features to convey information and ideas ACELY1725

Things you will need

  • Butchers paper and marker pens
  • Computers

Lesson description


  • What is pollution? Have a student lead a brainstorm and list all ideas.
  • Ask students to think about water pollution specifically – are there additional pollutants that we need to add to the list?
  • Watch the videos Water quality and pollution (2:47) and What is non-point source pollution (2:48).
  • Break students into groups of 4 and have them discuss the key points raised in the films. A scribe should make notes on paper. Main points to discuss include:
    • Water contamination can be classified into 2 groups:
      • point source contaminants that come from industrial discharges or sewage treatment plants
      • diffuse source (non-point source) contaminants, which includes runoff from agriculture and urban environments.
    • Frogs are bio indicators and are being impacted by water pollution.
    • Water pollution can come from water that flows off the land (runoff) contaminated with chemicals, pesticides, fertilisers and animal waste, mud from construction projects, leaf and grass clippings and items poured down storm drains.
  • Have a speaker from each group report back to the class on their findings.


  • As a class discuss – what are nutrients?
  • Explain to students they are to investigate the issue of nutrients, which runoff from agriculture and urban sources into our waterways.
  • Students are to plan, draft and produce a project, exhibit or performance to demonstrate their understanding of the topic. Suitable formats could include a written report, video, presentation, community educational game, a 3D model, play or opera. Their work must answer the following questions:
    • What are nutrients and where do they come from?
    • What effect do they have on our waterways?
    • Why must we reduce them and how can it be done?

Reflect & summarise

  • Students perform or explain their work to the class.
  • Together with students, summarise the points raised and provide feedback.

Extension activities

Teacher background information

Our rivers and estuaries are under increasing pressure from land use change, altered aquatic habitat, competition from exotic species, changes to flow regime, pollution and a changing climate.

What are nutrients?

Nutrients are elements or compounds including nitrogen, phosphorus and organic carbon. They enter rivers from 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.


Eutrophication (high concentrations of nutrients) can be either natural or caused by human impact. When humans alter the landscape by clearing vegetation there may no longer be enough vegetation around rivers and estuaries to absorb excess nutrients before they enter these waterways. This problem is exacerbated by the addition of extra nutrients onto the land in the form of fertilisers and animal manure and by changing the types of plants present.

What is the problem with nutrients?

Nutrients are essential for plant growth, including algae. However excess nutrients fuel algal blooms and can promote harmful algae. When an algal bloom collapses, the algal cells fall to the riverbed. Here, bacteria break down the algal organic matter from the catchment. This process takes oxygen out of the water and the greater the amount of organic matter in the system, the greater the amount of oxygen that is removed from the water. This can result in low oxygen conditions.

Low oxygen conditions can result in nutrient release from the river sediments, which can favour toxic algal blooms. Low oxygen conditions and toxic algal blooms may result in fish deaths.

What can we do to help?

  • Fertilise wisely by limiting fertiliser application and only applying a river-friendly variety. Ensure that you never overwater.
  • Do not dispose of items in drains, as these lead to our waterways.
  • Wash your car on the lawn to keep detergents out of the stormwater drainage system.
  • Grow local native plants, which need less water and fertiliser.
  • Take your rubbish home when you are out enjoying the rivers.
  • Pick up your dog’s waste and put it in a bin.
  • Check with your local council where to dispose of paint, oil and chemicals.
  • Use phosphorus-free detergents when washing clothes or dishes.
  • Compost your leaves and grass clippings.

Did you know?

In the early days of the Swan River Colony it was common for household rubbish, including sewage to be dumped into the Swan River.

Key vocabulary

  • Biological (bio) indicator: Species that can be used to monitor the health of an environment or ecosystem
  • Contaminate: To make something impure by exposing it to or adding in a poisonous or polluting substance
  • Eutrophication: The condition where a river or estuary has a high concentration of nutrients
  • Nutrients: A substance that provides nourishment essential for the growth and maintenance of life
  • Pollution: The act of contaminating or polluting the environment with unwanted substances or items (either intentionally or accidentally)
  • Surface runoff: The water flow that occurs when the soil is infiltrated to full capacity and excess water flows over the land