Water

There is the same amount of water on earth now as there was when the earth was formed, and there will always be the same amount in the future. It may seem as though the amount of water has declined due to huge reductions in our water reserves, however these reductions are only a result of an increase in the number of uses for water.

Water is contained in many forms on earth, not just as what comes out of your tap. All living organisms (animals and plants) contain large percentages of water. Therefore, water is never really lost, it is just being stored for another purpose. Reductions in our water reserves are also due to human induced changes in the landscape, such as irrigation and damming which use vast quantities of water for agriculture, industry and domestic use, and due also to a boom in population growth. The more things that require water inevitably lead to a reduced share of it per capita, which is why the amount of potable water on earth has become an issue.

Water is now regarded as one of our most precious resources, due to its scarcity and dependence on it for survival. It is now widely understood that current water wastage practices need to stop, and we need to identify how we can use it more wisely for the same result. To find out how you can save water at home, visit the Melbourne Water - Home Water Investigator website.

The Hydrologic Cycle explains the processes involved in cycling water around the globe. This cycle is a naturally occurring process involving the constant movement of water above, on and below the earth’s surface. This movement of water is only made possible due to the changes in its structure from liquid to gas to solid. Water evaporates from the large water masses on earth, such as oceans, seas and lakes, and rises to form vapour in the air, which can eventually be seen as clouds when the droplets increase in size. When the moisture droplets become too heavy, they fall on the earth as precipitation, which either infiltrates into the soil or runs off the land surface into creeks and rivers. The water in the creeks and rivers eventually flows back out into the ocean, where evaporation into the atmosphere occurs again.

Water which infiltrates into the soil is either used by plants for growth and survival, or it moves past the root zone of plants to become groundwater. Groundwater is stored in aquifers, which may be anywhere from a few metres to many kilometres under the earths surface. It is for this reason that aquifers can take hundreds of years to renew storage levels.

Water on earth is contained as either salt water or fresh water (Figure 1). 97% of water on earth is saltwater and 3% is freshwater. The 3% of freshwater is made up in the following parts: 2.25% in polar ice caps and glaciers, 0.6% in underground aquifers and 0.15% in streams, lakes and the atmosphere. In comparison to the total amount of water on earth, it is hard to imagine how available freshwater storage levels could continue to provide for the needs of the present, let alone the needs of future generations and growth in the global population.