Water sources

Lake surrounded by trees

Our drinking water comes from the natural environment.

All water comes from the environment and flows through the natural water cycle.

People manage this water cycle to make sure we have a safe and reliable water supply. Managing water in this way creates the  urban water cycle. The urban water cycle takes water from many sources.

The main source of drinking water for many people around the world is from rivers. Rivers drain water from the land around them. This surrounding land is called a river catchment.

Dams are built across rivers to catch and store water for later use. Water is pumped from dams through pipes to water filtration plants and then to storage  reservoirs.  From there, it mostly flows by gravity to people’s homes, schools and businesses in pipes called water mains.

Some rain falling in catchments infiltrates into the ground and is called groundwater. This groundwater can be used by people who build wells or bores to reach the water under the ground.

Oceans have also become a source of drinking water for many people around the world. Desalination is the process used to turn seawater into drinking water.

What are the main water sources?

A catchment is an area of land, usually surrounded by mountains or hills, where all rainfall that runs off the land, flows to a common point.

When rain falls in a catchment, it flows by gravity downhill either over the surface or under the ground towards the ocean.

If the water flows on top of the ground it's called surface water. If it soaks into the ground by infiltration it collects in aquifers and becomes groundwater. Surface water and groundwater flow into waterways like creeks and rivers or can be stored in water bodies like lakes, lagoons and wetlands. This freshwater eventually flows into the ocean where most of the earth's water is found.

Aerial view of lake surrounded by bushland

Most of Sydney’s drinking water comes from the Blue Mountains and the Southern Highlands.

The Hawkesbury-Nepean River system is the source of the largest volume of Sydney’s drinking water. This river system includes the Hawkesbury–Nepean River and all the smaller rivers that flow into it. They make up an area called the Hawkesbury-Nepean catchment. This large valley of over 22,000 km2 is larger than the whole of greater Sydney.

The land use within a catchment affects the quality and amount of water in a river. It's important that all land use is managed carefully to make sure rivers remain healthy. Managing the impacts of all the activities around a river and its catchment is called total catchment management.

WaterNSW protects the health of our drinking water catchments. This ensures a reliable source of quality, fresh water is available for us to filter and supply to the people of Sydney, the Illawarra and the Blue Mountains. Find out more about managing catchments.

Play the Catchment Detox game and take on the challenge to manage a river catchment and create a sustainable and thriving economy.

Rain falling in river catchments is the main source of Sydney’s drinking water.

Dams are built across rivers to catch and store water to give us a more permanent and reliable water supply. Dams store water in an area behind the dam wall. This is often called a storage reservoir.

WaterNSW manages and protects five drinking water catchments in the greater Sydney area. These catchments provide the source water for 11 major water supply dams that supply water for Sydney, the Illawarra and the Blue Mountains. 

Sydney's dam water is filtered at one of our nine water filtration plants to make sure it’s of excellent quality, clean and safe to drink.

Warragamba Dam is Sydney’s largest dam. It provides about 80% of greater Sydney's water supply. The dam collects water from the Wollondilly and Coxs river systems and forms Lake Burragorang behind the dam wall.

Warragamba Dam is 65 km west of Sydney in a narrow gorge on the Warragamba River. It's the largest urban water supply in Australia and one of the largest domestic water supply dams in the world. It holds four times more water than Sydney Harbour when it's full.

Learn more about water supply catchments and dams at WaterNSW.

Dam levels

Warragamba Dam’s water level rises and falls depending on the amount of:

  • rainfall in its catchment
  • water used by people in Sydney.

Since it was built in 1960, the lowest dam level reached was 32.4% on 10 February 2007. This occurred during a drought known as the Millennium Drought which lasted from 1996 to mid-2010.

We're currently in one of the worst droughts on record. We've had some rain, but it's important we continue to conserve water. Learn more about water use and conservation.

Visit WaterNSW to check  dam levels or check on rainfall and dam levels in the Greater Sydney Catchment.

Warragamba in drought January 2020 showing bare banks

Warragamba dam in drought (mid January 2020). Dam levels were about 42%.


Cliffs along the coastline

97% of all the water on Earth can be found in seas and oceans.

The ocean can be used as a source of drinking water. Unlike rivers and dams, the amount of seawater in oceans is not affected by changing rainfall.

Desalination is the process of removing the salt from seawater to produce drinking water. It is a way to make sure people have enough water when:

  • countries do not have rivers that are easy to get to
  • countries are affected by drought
  • rainfall isn't adequate
  • populations grow faster than existing water supplies.

In response to the Millennium Drought, the NSW Government commissioned the Sydney Desalination Plant on the coast at Kurnell, between Botany Bay and the Tasman Sea.

Desalination has provided an extra source of water for Sydney that doesn't rely on rain. It's an important part of the NSW Government's plan to make sure we have enough water for the future.

The desalination plant at Kurnell can provide up to 15% of greater Sydney's drinking water needs when dam levels fall below 60%, as outlined in the Metropolitan Water Plan.

At full capacity, the plant can produce a yearly average of 250 million litres a day, which is about 15% of Sydney’s total water usage.

Water from the desalination plant must meet the Australian Drinking Water Guidelines and Sydney Water’s standards. When the plant produces water that meets these standards, we'll add it to our system.

To find out more, visit  Sydney Desalination Plant.

In Australia and in many other countries, water is scarce and people have developed many ways to collect and store water. Many people, particularly in rural areas, rely on a variety of water sources other than rivers and oceans. These include groundwater, rainwater tanks and recycled water.


Groundwater is water located beneath the Earth's surface.

Groundwater collects in aquifers that are the spaces in rocks and between grains of sand and gravel. Groundwater slowly moves through these aquifers and flows into rivers, streams, lakes and wetlands. The top of the groundwater is called the water table.

Aquifers can store large quantities of water and can be the main source of water, particularly in dry areas. If groundwater is used in a sustainable way, it can be an important part of a city's water supply system.

Learn more about Groundwater use from NSW Health.

Rainwater tanks

Metal rainwater tank

Rainwater tanks collect water that you can use in your garden.

Rainwater tanks can be a water source for drinking, flushing toilets, washing clothes or watering gardens. However, in urban areas it's usually unsafe to drink tank water.

This is due to higher levels of pollution in the atmosphere which could pollute the tank water. NSW Health recommends that people use their public water supply for drinking and cooking because it's filtered, disinfected and generally fluoridated.

After long periods of drought, many people in greater Sydney installed rainwater tanks. This water is used to water gardens and flush toilets, and helps conserve our drinking water resources. 

Learn more about Rainwater tanks from NSW Health.

Recycled water

Recycled water is water that's been used before.

We take wastewater or stormwater and clean it to a high standard so it can be returned to homes and businesses and safely used again.

We currently use recycled water in greater Sydney for things like:

  • watering sports fields, lawns and gardens, including fruit and vegetable plants
  • flushing toilets
  • washing cars
  • filling ornamental ponds
  • fighting fires
  • washing laundry in a washing machine (you need the right plumbing for this)
  • making liveable cities
  • manufacturing.
We expect to use more recycled water in the future.

In Sydney we don't currently use recycled water for drinking, but there are many cities around the world that do. Their recycled water is treated to a very high standard and is safe to drink. Some places you might like to learn about are Perth and Singapore.

Learn more about water recycling in greater Sydney.