3.5 Uses and abuses of underground water

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USES AND ABUSES OF UNDERGROUND WATER


Curriculum Alignment ACT ELAs 2, 14, 18, 19, 20 NSW KLAs Years K-6: Science and Technology, Mathematics, HSIE. Years 7-10: Geography, Science, History Years 11-12: Agriculture, Community & Family Studies, Geography, Earth and Environmental Science, Society and Culture QLD KLAs SOSE, Science, Geography SA ELs Futures, Interdependence, Thinking VELS Science, Thinking Processes, Geography

Objectives
>Students gain an understanding of how water is stored in an aquifer
>Students get to demonstrate how groundwater can become contaminated
>Students are made aware of how surface water and groundwater are connected

Duration
30 minutes

Materials required
>One clear plastic cup or bowl per student
>One piece of modelling clay or floral clay that will allow a flat ‘pancake’ to be made for their cup by each student
>White play sand that will measure 1cm in the bottom of each cup
>Red food colouring
>One bucket of clean water and small cup to dip water from bucket
>Aquarium gravel (natural colour if possible) or small pebbles (approximately 1/2 cup per student)

As many small rocks
may have a powdery
residue on them,
you should rinse the
aquarium gravel
and dry it on a clean
towel prior to use. It is
best if they don't add
cloudiness to the water.

Many wetlands on floodplains are connected to groundwater systems as well as surface waters. Photograph: Bill Phillips

Background
Many communities obtain their drinking water from underground sources called aquifers. Water suppliers, landholders, parks and gardens managers etc, drill through soil and rock into aquifers to access groundwater reserves for domestic uses, stock watering and irrigation, depending on the quality.

Unfortunately, groundwater can become contaminated by a range of products and from various sources. These chemicals can permeate through the soil and rock, polluting the aquifer. Such contamination can pose a significant threat to human health.

In Australia, surface water and groundwater are intimately connected in many locations. An emerging issue in some regions is determining whether or not the groundwater reserves are being used sustainably. Over-extraction can have ‘ripple’ effects for river and wetland health.

Efforts are now being made to map aquifer systems and establish their sustainable yield. In some areas there are now programs to cap bores to reduce the drawdown of water levels. State, and some local governments are also introducing licensing arrangements to manage the number of bores and the volumes of water being extracted.

Vocabulary
Confining layer
Aquifer
Groundwater

Procedure
1. Pour 1cm of white sand into each bowl completely covering the bottom of the container. Pour water into the sand, wetting it completely (there should be no standing water on the top of the sand). Let students see how the water is absorbed into the sand, but remains around the sand particles as it is when stored in the ground and forming part of an aquifer.

2. Have each student flatten the modelling clay (like a pancake) and cover 1/2 of the sand with the clay (have each student press the clay to one side of the container to seal off that side). See illustration below. The clay represents a ‘confining layer’ that keeps water from passing through it. Pour a small amount of water onto the clay. Let the students see how the water remains on top of the clay, only flowing into the sand below in areas not covered by the clay.

3. Use the aquarium gravel to form the next layer of ‘earth’. Place the gravel so it completely covers both the sand and clay. To one side of your bowl, have the students slope the gravel, forming a high hill and a valley (see illustration). Explain to the students that these layers represent some of the many layers contained in the Earth’s surface.

Now pour water into your aquifer until the water in the valley is even with your hill.

Stream salinisation. Land clearing in the surrounding area has seen the watertable rise and now highly saline water is sitting in the stream bed. The surrounding trees have been ‘poisoned’ by the saline groundwater. Photograph: Bill Phillips

4. Students will see the water stored around the gravel. Explain that these ‘rocks’ are porous, allowing storage of water within the pores and openings between them. They should be able to observe a ‘surface’ supply of water (a small lake) has formed. This will give them a view of both the ground and surface water supplies.

5. Use the food colouring and put a few drops on top of the ‘rock’ hill as close to the inside wall of the bowl as possible.

6. They will see that the colour spreads not only through the ‘rocks’, but also to the surface water and into the white sand at the bottom of their cup. This is one way pollution can spread throughout the aquifer over time.

Extension
Get the class to assume that there is an aquifer under the school (as there probably is!) and have the students list the activities happening in the school and across the surrounding community that could potentially pollute their aquifer.

Secondary pathway
Have students walk around their own neighbourhoods noting signs in gardens indicating ‘Bore water is in use’. How many are there? Get them to inquire with the relevant authorities how to go about getting approval for getting a bore? What did they discover about how easy or difficult this is?
Ask them to speculate on the impact of this use of groundwater on local waterways, assuming there is a close connection between the groundwater and surface waters in rivers, streams and wetlands.