Stormwater systems

Rain's too valuable to go down the drain

Managed properly, stormwater is a valuable resource that can enhance cities' liveability, sustainability and resilience. We do it by working with local government authorities (LGAs) to improve the health of our waterways, provide opportunities for stormwater reuse and protect people and properties from flooding. So how do we manage stormwater, and how do we redirect it?

Our stormwater systems

Urban environments are packed with hard surfaces such as roofs, roads and footpaths that prevent rain from soaking into the ground. Stormwater is the water that flows on those surfaces after rain. Often it flows from property drains to street gutters operated by local councils, and these may connect to our large channels, pipes and creeks. This is what forms the stormwater drainage system.

Our stormwater systems provide services to about 645,000 properties. They consist of:

  • 73 catchments
  • 455 kilometres of channels and pipes
  • over 70 stormwater quality improvement devices.


Are you in one of our stormwater catchment areas?

We also manage flood-prone areas and trunk drainage in the Rouse Hill area. Find out more about:

Stormwater safety

Only authorised maintenance crews can safely enter our stormwater systems, which include open channels, drains and underground tunnels. These are dangerous because:

  • water can rise quickly and unexpectedly, even when it’s not raining in the immediate area
  • flowing water is powerful and can knock people over, even when it's shallow
  • stormwater contains pollutants, including dangerous chemicals and disease-causing bacteria.

Report unauthorised access to stormwater systems
If you see anyone entering a stormwater drain, channel, tunnel or maintenance hole, call us on 13 20 90 24/7. We'll keep your contact details confidential, and you may prevent an accident or death. We’ll investigate all reports of entry to our stormwater systems and refer them to the police or other authorities.

Flooding in Greater Sydney

Heavy or prolonged rain can cause creeks and coastal rivers to rise quickly. It can take only minutes for waterways to pose a major flood hazard. Fast-moving floodwaters in populated areas are a serious risk to life and property.

Flash floods are the most dangerous type of flood, and result from short, extremely intense bursts of rain. They often occur in heavily populated areas with little or no warning. In contrast, rivers in western NSW generally flood slowly, usually taking weeks and months to fully develop. This can lead to major property damage and isolation of entire communities. Floods are Australia’s most costly and predictable natural disaster.

This difference in speed and duration of flooding is caused by:

  • soil type
  • storm length and intensity
  • topography (or landscape)
  • land use and development (hard surfaces increase run-off speed in urban areas).

We help prevent flooding in many ways.

Our stormwater assets are located across 23 LGAs in Greater Sydney, and we work closely with these LGAs to reduce the impact of flooding on the community. We also offer our expertise in stormwater catchments outside our areas of responsibility.

Protecting stormwater assets

We protect our stormwater assets so they work as intended. We regularly check the structure and operation of our assets and maintain or renew them. This is a key part of how we manage flooding.

Assessing development applications

Sydney Water assesses all development applications near our stormwater assets. Sometimes proposed developments can be impacted by flooding or make flood risk worse for others. If this happens, the developer needs to propose alternative designs and consult with LGAs and Sydney Water.

Participating in Floodplain Risk Management Committees

We participate in Floodplain Risk Management Committees with local councils, communities and other agencies, outlined in the NSW Government Floodplain Development Manual. These committees oversee the preparation of:

  • flood study to identify and quantify local flooding
  • floodplain risk management study to assess the options to address flooding
  • floodplain risk management plan to prioritise measures that will reduce flooding.

Collaborating with LGAs in Greater Sydney

We play an active role in the stormwater industry, and participate in many council and community events to address flooding. We contribute by sharing our knowledge, offering advice and discussing proposed modifications to the stormwater system.

Stormwater quality

Stormwater can carry pollution like litter, sediment, grease, oil and metals that are picked up from roads and properties. This pollution affects the quality of our local waterways. We've installed over 70 stormwater quality improvement devices (SQIDs) to help clean stormwater. These include trash racks, sediment traps and litter booms.

If you're connecting to our stormwater pipes or developing your property, you must meet our stormwater quality targets.

Stormwater harvesting

Stormwater harvesting is the practice of collecting, storing and treating stormwater from urban areas. It's collected from stormwater drains or creeks, rather than roofs, and treated so it's safe to use as recycled water. Then, it's commonly used to water public parks, gardens, sports fields and golf courses.

Benefits of stormwater harvesting are that it:

  • reduces the demand for drinking water by replacing it with recycled water produced from stormwater harvesting
  • reduces stress on urban streams and rivers by capturing some of the pollutants and nutrients that would otherwise enter waterways from stormwater flows
  • enables users to access an alternative source of water for non-drinking use
  • increases opportunities for sustainable water management, which is an important consideration in water-sensitive urban design (WSUD).

You may want to investigate setting up your own stormwater harvesting scheme.

We work with local councils and other agencies to manage stormwater and investigate opportunities for stormwater's collection and reuse. It's one of the many ways the NSW Government is securing Sydney’s water supply for a growing population.

There's a lot of advice and assistance available if you want to set up your stormwater harvesting scheme from our stormwater system. Find out more about what you need to do from our Stormwater harvesting fact sheet. You can also review our Stormwater harvesting and reuse agreement.