Teacher background information
Water is continuously circulated through a global cycle powered by the sun and the rotation of the earth. This is called the water cycle. With exposure to the sun and the wind, water evaporates from the ocean and is blown by the wind over land as vapour in clouds; given the right conditions, it then precipitates as rain, hail or snow.
The water can then either:
- return to the atmosphere through evaporation or transpiration by vegetation
- flow back into the sea via streams and rivers
- be stored in lakes and dams
- infiltrate into the ground, where it may be stored, or move slowly to eventually be discharged back into the sea.
Our water sources
Drinking water in WA comes from 3 major sources: surface water, groundwater and desalination. The Perth metropolitan area is supplied by the Integrated Water Supply Scheme, which also supplies Mandurah, Pinjarra, Harvey, Waroona, Binningup, Myalup, Yarloop and towns serviced by the Goldfields Pipeline. It is called an integrated scheme because water is drawn from an integrated network of dams, groundwater and seawater sources.
In some northern metropolitan areas, water supplied is from groundwater sources alone, while in other areas of Perth, the supply may be from dams or a mixture of sources. Water from all sources is treated by Water Corporation to ensure it meets stringent drinking water quality regulations.
Dams servicing the metropolitan area include Canning, Serpentine, North and South Dandalup, Wungong, Victoria, Bickley and Churchmans Brook. Mundaring Weir provides water to towns along the Goldfields Pipeline, to agricultural districts, and at times to Perth.
Other major dams in WA include Harris Dam, which supplies water to 32 towns in the Great Southern region, and Harding Dam near Roebourne, which supplies towns in the West Pilbara region including Karratha.
Groundwater is water that occupies the spaces between particles of soil (sand, silt and clay) or rock beneath the earth’s surface. The source of groundwater is rain, which infiltrates the soil. Groundwater moves quickly through sandy soils and reaches the water table. As a result, large volumes of groundwater can often be pumped from wells (bores) sunk in sandy soils.
The Perth Seawater Desalination Plant began operating in 2006. Located in the Kwinana industrial area, the plant supplies desalinated water to the Integrated Water Supply Scheme. In 2011 a second seawater desalination plant was built at Binningup in the South West.