Water catchments

What is a catchment?

A catchment is the area of land that drains into the one waterway (creek or river). Whatever happens in that catchment, affects that waterway. Rainwater runs off roofs, roads and footpaths becoming stormwater which picks up pollution along the way. This water eventually ends up at the bottom of the catchment.

Everyone lives in a catchment and can  help improve the quality of local waterways. It is up to everyone to keep local waterways clean.

Inner West Catchments

The Inner West Council area is mainly within two water catchments.

  • The Cooks River Catchment
  • The Lower Parramatta River Catchment

Inner West Council, the Cooks River Alliance and Parramatta River Catchment Group have a shared vision of making our rivers and waterways swimmable again. Preventing large, small and chemical pollutants from entering the waterways in the first place is the best way to do this. This can be achieved with help from the community.

You can help by building water-sensitive design elements on your property or installing a water tank.

Gross Pollutant Traps (GPTs)

What are GPTs?

Gross pollutant traps (GPTs) are one way to treat stormwater before it enters local waterways. Inner West local government area falls within three catchments:

  1. Lower Parramatta River catchment in the north west that flows into Sydney Harbour
  2. Sydney Harbour in the north
  3. Cooks River in the south that flows into Botany Bay

Inner West Council has 23 GPTs that play an important role in removing large (gross) pollutants greater than 2mm from stormwater runoff. 

Plastic bags, plastic bottles and takeaway food containers are the most common types of litter found in GPTs, followed by garden waste.

GPTs are an end solution to the problem of waste entering our waterways. They are expensive to construct and require maintenance that cost more than $80,000 in 2015/16.

Examples of GPTs

Here are some examples of different types of GPTs installed along the Cooks and Parramatta Rivers. 

Diversion system

Diversion system

The *red* arrows show how large items sink to the bottom of the GPT, the *blue* arrows show how sediment is trapped, and the *yellow* arrows show the path of stormwater. This is based on an illustration by Rocla, who manufacture GPTs.

End of pipe net

End-of-pipe net

An end-of-pipe net GPT, located in Marrickville.

Floating boom net

Floating boom net

A floating boom net GPT, located in Earlwood.

Trash rack

Trash rack

A trash rack GPT, located in Marrickville.

GPT data

Visit the GPT data page to see the amount of waste collected by Council's GPTs before it enters the Cooks River, Parramatta River, and Sydney Harbour.

The GPTs are visually inspected and cleaned monthly.

The journey of litter

See how far litter can travel in our waterways.

Parramatta River and Sydney Harbour

The journey of a plastic bottle from Hawthorne Canal to Balgowlah Heights.

Parramatta river and harbour map

The Cooks River   

The voyage of a plastic bottle along the Cooks River.

Cooks river map

See other infrastructure that prevents litter entering waterways

Sydney Water’s litter boom traps stop the movement of litter once it enters a waterway. Litter booms help because it would be far too costly to install a GPT on every stormwater outlet. See the amounts of litter collected by the litter booms near you.

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Page last updated: 17 Feb 2020