Streamwatch: The managed water cycle
The natural water cycle has been modified by people to ensure a constant water supply and the safe disposal of wastewater.
The managed water cycle involves:
The water supply system, which
- uses dams to store water
- treats water at water filtration plants
- stores water in reservoirs
- can include using desalination to provide a more secure water supply
- provides water to our homes, schools and businesses through pipes and pumps.
The wastewater system, which
- removes wastewater from homes, businesses and industry through the wastewater system
- treats wastewater at wastewater treatment plants or water recycling plants
- returns treated wastewater to waterways or recycles it for further use.
The stormwater system, which
- returns stormwater to local waterways
- removes some debris and rubbish
- re-uses stormwater for industry and irrigation.
Secondary storage dams hold water, which is available for transfer to the major storage dams. Water storage dams
hold large amounts of water for use over time, particularly in dry conditions. The dams also allow time for many of the contaminants, which are picked up by the water as it runs through the
catchments, to settle out.
Water filtration plants
On leaving the dams, the water passes to water filtration plants. The filtration plants are designed to further improve
the quality by removing identified contaminants which are set down in each plant’s performance targets. These
are to ensure the water meets quality and health guidelines.
Customer supply systems
From the filtration plant, water enters a complex series of pipes and reservoirs for delivery to homes and businesses. Each filtration plant may supply one or more customer supply systems.
A desalination plant uses reverse osmosis technology to extract fresh water from sea water. After screening and pre-treatment to remove any solids and sediment, the water is pushed through membranes under high pressure. Fresh water passes through the membranes and the remaining sea water concentrate is returned to the sea. The water is then treated to meet Australian Drinking Water Guidelines and transferred to a tank, ready for supply to customers.
Warragamba Dam supplies 80% of Sydney’s water supply. The lake behind the dam holds 4 times the volume of water of Sydney Harbour.
Greg McDonald , Education Project Officer - Streamwatch