Science 7–10 · Year 8

Aquifer in a tank: water table, wells and a leaking pollutant

Science understanding: Earth and space sciences (NSW Science 7-10 has no content point on groundwater; coded to the Stage 4 focus area Change through its content point on comparing the observable properties of rocks, here the permeability of gravel, sand and clay layers, and to ACARA's use of sedimentary rocks, AC9S8U04)

PracticalLow risk

The idea

Rain soaks into permeable layers and collects above impermeable ones; a well draws the water table down into a cone, and anything spilled at the surface follows the flow to the well.

What you need

1 clear plastic tank (about 30 x 20 x 20 cm) per class or group
layers as in the Earthlearningidea sponge model (two or three porous sponges with one sponge sealed in a plastic bag as the impermeable layer) or a sand-gravel-clay build: 4 cm gravel, a 1 cm clay band on half the width, 6 cm sand
1 clear straw or rigid tube as the bore, 1 20 mL syringe for pumping, food colouring as the pollutant, a watering can or jug as rain
1 ruler taped to the tank wall to read the water table

How to do it

Predict, then pour dyed water slowly over the surface and watch it fill the pores from the bottom up; read the water table height on the ruler after each 200 mL.
Insert the bore to the base and pump with the syringe; read the water level in the bore and beside it as the cone of depression forms, then watch it recover.
Add three drops of a second colour at the surface uphill of the bore and rain lightly; record how long the colour takes to reach the bore water.
Where a sealed sponge or clay band sits, note where water flows around it and where a perched water table forms above it.
Sketch the tank with the water table, the cone of depression and the pollutant path.

What you should see

The water table rises about in proportion to the volume added divided by (tank area x porosity); pumping lowers the level most at the bore and less with distance, the cone shape the Earthlearningidea describes, and the level recovers after pumping stops. The pollutant colour travels with the flow toward the bore and appears in the pumped water, faster in gravel than sand; water does not enter the bagged sponge or clay band and either flows around it or perches above it. The learner knows it worked when the bore water changes colour after the surface spill and the cone is visible in the dyed water while pumping.

What changes

What you change: pumping rate and position of the spill
What you measure: water table shape and time for the pollutant to reach the bore
What you keep the same: layer thicknesses
rain volume
tank size

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

Groundwater is an underground lake or river; it fills pore spaces.
A bore takes water from directly beneath it only; it draws from a cone that reaches out from the bore.
Pollution stays where it is spilled; it moves with the groundwater to bores and rivers.

Safety card

Low riskLearners carry it out

Hazards

water spills
food colouring stains

Controls

work over a tray
aprons

Note

No hazardous chemical and no flame or heating apparatus: a generic classroom risk assessment (CSIS 1.7 or RiskAssess) covers trips, spills, warm lamps and sharp edges.

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

Science 7-10 Syllabus (2023), NSW Education Standards Authority (implemented from 2026; codes read at curriculum.nsw.edu.au on 22 and 23 September 2026)SC4-CHG-01 SC4-WS-02 SC4-WS-04
Australian Curriculum v9AC9S8U04AC9S8I02

Sources

The pages the author read to write this activity.

All Concept Studio activities