By investigating (estimating and / or calculating) the percentage of available fresh water on Earth then discussing and exploring the implications of their findings, students understand that this resource is limited so must be conserved and managed sustainably, on personal, local and global scales.

Use this activity with "Comparing Apples and Earth" to introduce or stimulate discussion about the themes of sustainable resource management.

Materials:

»	water
»	globe and /or world map
»	1000 ml beaker / cylinder
»	100 ml graduated beaker
»	small dish or beaker
»	dropper or glass stirring rod
»	food dye
»	salt
»	small bucket
»	copies of Water Availability table

Method:
Note: Discussion points in italics

1.	Fill a 1000ml container with water. If demonstrating to a class, colour the water with a few drops of food dye so it is easier to see. This represents all the water on Earth. Ask where most of this water is located - refer to globe or map. Ask students to estimate the amount of salt water on the Earth's surface.
2.	Pour 30 ml from the 1000 ml into the graduated beaker - this represents the 3% of the Earth's water that is fresh. Put salt into the remaining 97% to simulate the water in the oceans, unsuitable for human consumption. Consider the 30ml remaining. In what state is that remaining 3%? What is found at the Earth's poles? Again ask for an estimate of how much water is frozen at the Poles.
3.	Pour 6ml of the fresh water into the small dish or beaker. The remaining 24ml can be placed in a freezer or frig if one is nearby, or otherwise simulate ice, eg. pour into an ice cube tray. Almost 80% of the Earth's fresh water is frozen in ice caps and glaciers. The amount of water in the small container (approximately 0.6% of the original amount) represents non-frozen fresh water. Only about one quarter of this is surface water; the rest is underground.
4.	Use a dropper or stirring rod to take a single drop of water. Release this into a small container, eg a small metal bucket so students can listen for the "drop". This represents clean, fresh water that is not polluted or otherwise unavailable for use - about 0.003% of the total. This precious drop must be managed with care.
5.	Discuss the conclusions students have drawn from the demonstration. Many will have concluded that there is only a very small amount of water available for humans. In fact, on a global scale the single drop actually represents a large volume of water - but … See suggestions for further discussion and activities.
6.	Use the Water Availability table to calculate the actual amount of fresh water available per person.
7.	Have some fun with the poem "Recycled".

Water Availability Table:

Discussion:

»	Discuss global distribution of water. Why does more than one-third of the world's population not have access to clean water?
»	Investigate the factors affecting water distribution on Earth (land forms, vegetation, proximity to large areas of water, role of oceans, etc). Have class work in small groups and report back to share their findings.
»	Explore other environmental and natural influences on the availability of water (droughts, floods, pollution, etc). Research current events, conditions and activities affecting the availability of water, - locally, in Australia and elsewhere in the world.
»	Discuss long term events, activities and behaviours which will reduce the amount of fresh, potable water available for human consumption. Consider at a local and global scale. Consider other users of water, apart from humans.

Resources:
SaveWater website is a good place to start, providing links to other resources and some great ideas for discussion and action.
» www.savewater.com.au

See The Water Cycle activity and other resources available on our website:
» http://www.landlearn.net.au
» http://www.landlearn.net.au/print/water_cycle.htm

Acknowledgment: This activity is adapted from Project Wet Curriculum & Activity Guide 1995 Montana State University.

Answer Key:

Water Availability table based on a global population of 6.3 billion