Water as a Resource

Outcomes:

Draw and label the water cycle
Identify the processes that drive the water cycle; evaporation, condensation, precipitation, transpiration
Identify that water is an important resource that cycles through the environment.
Explain the physical processes involved in the water cycle.
Demonstrate how understanding the water cycle has influenced water management practices.
Understand the application of separation techniques in treating sewage and making water suitable for drinking.
Explain how the water cycle affects households, industrial, agricultural uses of water and management practices.
Understand how Aboriginal and Torres Strait Islanders manage water resources.

About two-thirds of the Earth’s surface is covered with water, yet in Australia we have very little fresh water. How can this be?

Of all the water on the Earth, 97.5% is salt water—the remaining 2.5% is fresh water. If salt water is drunk it will make you very ill as it is too salty for the human body to digest. By drinking it you would become thirstier than before you drank. Sailors who made long journeys of exploration on sailing ships could collect rainwater but they did not have the technology to produce fresh water from sea water.

Of the tiny percentage of fresh water in the world, most of it is locked in ice caps and glaciers or in the soil. This leaves a very small percentage of the Earth’s water, less than 0.01%, that is suitable for drinking.

The Global Water Cycle

The water cycle describes how water evaporates from the surface of the earth, rises into the atmosphere, cools and condenses into rain or snow in clouds, and falls again to the surface as precipitation.

Water on the Earth has always been naturally recycled. Like many other resources, there is only a certain amount of water on the Earth. Even when water evaporates and becomes a gas, it has not stopped existing—it is just invisible to the eye. It will come back in another form. This process is called the water cycle.

The amount of water on earth has been constant for a very long time. Water travels the earth in a constant cycle through atmosphere, land mass and oceans. In the water cycle, heat energy from the sun evaporates water from lakes, rivers, oceans and the land itself. Water vapour is also lost from the leaves of plants in a process called transpiration and from animals through respiration. As the water vapour rises, it is cooled by the air and will condense into tiny water droplets. The water droplets rise in the atmosphere, form clouds and combine to form larger droplets, which fall as rain, hail or snow (the different forms of precipitation). In this way, the same water that evaporated is returned to the land (surface runoff), flowing through rivers and finally returning to the oceans. Some of the water may be stored underground in aquifers.

Factors affecting the speed of water through the water cycle:

- - state
  - air temperature
  - humidity
  - air movement
  - landscape
  - vegetation
  - sunshine

Australia is the one of the world’s driest continents. We store more water than any other country—more than 4 million litres of water per person! Australia requires such a large storage capacity to ensure a reliable water supply during regular and long periods of drought. Water is captured, stored and treated, then distributed through pipes. It is used in households, manufacturing, agriculture and mining.

Large dams and reservoirs have been built to collect and store water. The largest storage reservoir in New South Wales is the Warragamba Dam in Sydney (2 million megalitres, which is equivalent to 2 million million litres).

Water Uses

The main uses of water are for agriculture, industry and household use. Industrial use of water increases with country income, going from 10% for low- and middle-income countries to 59% for high-income countries. Source: WBCSD (2009)

Agriculture: In many developing nations, irrigation accounts for over 90% of water withdrawn from available sources for use. In England where rain is abundant year round, water used for agriculture accounts for less than 1% of human usage. Yet even on the same continent, water used for irrigation in Spain, Portugal and Greece exceeds 70% of total usage.

Industrial use: After agriculture, industry is the second largest user of water – be it for the production of electricity, as process water, for mining, as a means to dispose or discharge waste etc. The amount varies heavily depending on the type of industries, and so does the pollution resulting from its use.

Domestic use: By now, the water we use directly in our homes accounts for the smallest part of water use – yet it is essential for our survival: for drinking, preparing foods, and for washing ourselves. The consumption varies greatly – for example, from as little as 10 L per person an day in low-income areas in Ulan Bator (Mongolia) (World Bank 2010) to almost 600 L per person and day in the United States (WBCSD 2009). A minimum of 50 L per day as a basic water need is recommended (FALKENMARK 2005; WATER ENCYCLOPAEDIA 2010).

Water scarcity is a complex problem - it is one of unsustainable use, mismanagement and a lacking and holistic water governance. As so often, it is the life of the poor who are affected most: by water related disease, by degraded and dangerous environments, by a lack of food and water for hygiene. Almost one billion people do not have access to improved water sources, and 2.6 billion do not use improved sanitation options.

Aboriginal water management

Water treatment

Sydney Water: http://www.sydneywater.com.au/SW/index.htm

Water as a natural resource

Questions

Of all the water on Earth, how much can be used as drinking water?
How has the Australian government tried to preserve water sources?
Why is wastewater treatment important?
List the three major ways that humans use water.
What is the single biggest use of water in agriculture?
Give an example of an industrial use of water.
Why does golf use a lot of water?
What problems may result from serious water shortages?
More than 70 percent of Earth’s surface is covered by water. Why is scarcity of water the world’s most serious resource problem?
Relate droughts to water shortages. Explain why droughts are becoming more common.
Play the Melbourne Water Cycle Game: https://www.educationsoutheastwater.com.au/resources/melbourne-water-cycle-game

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