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An aquifer is like a sponge

About this lesson

Students are introduced to the concept of groundwater by experimenting with sponges and observing how they retain water like an aquifer.


Year level: 1, 2

Theme: Water supply


Learning objectives

Students can:
  • explain where groundwater is located
  • describe how a sponge holds water
  • discuss the results of their predictions and findings.

Curriculum links

Science

  • Pose and respond to questions, and make predictions about familiar objects and events ACSIS024ACSIS037
  • Use informal measurements to collect and record observations, using digital technologies as appropriate ACSIS026

English

  • Use interaction skills including turn-taking, recognising the contributions of others, speaking clearly and using appropriate volume and pace ACELY1788

Sustainability

Things you will need

  • Different sized sponges including a natural sponge
  • Ice-cream containers (equal to the number of sponges)
  • Polystyrene cups with holes in the bottom
  • Why does a sponge hold water? activity sheet
  • Different sized measuring cups

Lesson description

Discuss

  • What happens to water when it rains? 
  • Where does rain go?
  • What do you think happens to water that soaks into the ground?
  • Do you think we could collect this water and use it?
  • Show students the Groundwater animation video (3:43) to help them understand where water goes.
  • Explain to students that the class is going to do an experiment to find out more about how water is stored in the ground. The ground under our feet has similarities to a sponge.

Activity

  • Hand out dry sponges to the students. Ask – what does it feel like? (This is the ground before it rains).
  • Have students predict how much water their sponge will hold either using formal or informal measures.
  • Using the activity sheet in groups, predict which sponges will hold the most water.
  • Place each sponge into an ice cream container and use a cup with holes in the bottom to 'rain' water onto the sponges.
  • Get students to think about: Where did the water go? What happened when the sponge was 'full'? How could they tell?
  • Squeeze each of the sponges as tightly as possible to release all of the water into the ice-cream container.
  • Measure the volume of water collected by each sponge by pouring the water from the ice-cream container into a measuring beaker or use informal measuring (e.g. yoghurt pots).
  • Get students to record the volumes on the activity sheet. Were their predictions correct?
  • Now repeat the experiment with damp sponges and discuss: did they hold as much water as the first time when the sponge was dry? Why not?

Reflect & summarise

  • Where was the water in the sponges?
  • Did the largest sponge hold the most water? Did the natural sponge hold more water than a similar sized synthetic sponge?
  • What happens when the sponge gets too full of water? Can they explain how the sponge is like the ground? How is this related to what happens when we get too much rain?
  • Show the Australian floods video (1:02) (optional).

Extension activities

Book your class into a Water supply incursion.

Teacher background information

What is groundwater?

Groundwater is water that occupies the spaces between particles of soil (sand, silt and clay) or rock beneath the earth’s surface. The source of groundwater is rain, which infiltrates the soil. Groundwater moves quickly through sandy soils where it reaches the water table. As a result, large volumes of groundwater can often be pumped from wells (bores) sunk in sandy soils. Limestone is more porous than granite and holds more groundwater. Groundwater is found in unconfined (shallow) aquifers and confined (artesian) aquifers. Unconfined groundwater occurs near the land surface and receives direct rainfall recharge. Confined groundwater occurs beneath a layer of impervious material and may be under pressure.

The water table

The top surface of unconfined (shallow aquifer) groundwater is called the water table. The water table is usually below the ground surface. However, when the water table is high enough, groundwater comes to the surface naturally in springs, lakes and ponds (wetlands). The level of the water table may fluctuate, rising in winter after rainfall has recharged the aquifer, and falling during periods of low rainfall, when the volume of groundwater pumped increases or is drawn upon by vegetation.

Perth’s groundwater supply

Perth’s groundwater comes from artesian bores and two major groundwater mounds: the Gnangara Mound in the North and the Jandakot Mound in the South. This water is treated by Water Corporation at the following treatment plants prior to distribution to consumers: Wanneroo, Mirrabooka, Gwelup, Jandakot and Lexia. In addition to public water supply, privately owned bores in the Perth urban area draw another large groundwater supply. Groundwater pumped from these bores is used for irrigating domestic gardens, market gardens and public open space.

Resources

Did you know?

Groundwater is obtained from large natural underground storages called aquifers.

Key vocabulary

  • Aquifer: an underground layer of rock or sand that can absorb and hold water
  • Bore: a hole or passage in the earth made by a drill
  • Catchment: the surface area from which runoff flows, sometimes via drainage systems, to a river, dam or wetland
  • Groundwater: water that is held underground in the soil or rock
  • Porous: filled with holes that can absorb water
  • Saturated: holding as much liquid as can be absorbed
  • Surface water: water that is collecting either on the ground, in a stream, river, lake ,wetland, dam or ocean
  • Water table: the boundary between water-saturated ground and unsaturated ground