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Bay and catchments

Port Phillip Bay

Covering 1,950 square kilometres, Port Phillip is the entrance to Australia's busiest port and is one of Victoria's most popular recreational destinations. While relatively large in area, the bay is shallow with an average depth of 13 metres. The bay consists of a variety of habitats including sandy seafloor, seagrass beds and rocky reefs. Most of the seafloor is sand and silt which is home to a diverse variety of invertebrates (animals without backbones). These vast areas of sand are in some parts covered by dense seagrass meadows that provide important habitat for much marine life, especially young fish. Rocky reefs can also be found in the bay, often being dominated by hundreds of different seaweeds.
Studies show that Port Phillip Bay is a dynamic and self-sustaining ecosystem which is healthier and cleaner than comparable bays near large cities. The shallowness of the water aids aeration and the many marine plants and animals help to keep Port Phillip Bay in good condition.

Bay quick facts

  • Area: 1,950 square km.
  • Coastline: 264 km.
  • Name: Named after the first Governor of New South Wales, Arthur Phillip.
  • Ports: Port of Melbourne is Australia’s busiest port, supporting 15,000 jobs and $82 billion imports/exports. Geelong is Victoria’s largest regional port.
  • Home to: Up to 10,000 species of marine plants and animals including dolphins, penguins and the Weedy Seadragon.
  • Industries: The $10 million commercial fishing and aquaculture industries are dependent on the bay’s clean water.
  • Recreation: Visitors enjoy the coastal parks and beaches, boating, swimming, fishing and diving.

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Catchment waterways

Port Phillip Bay’s catchment covers over 9,790 square kilometres in area, and consists of 21 natural drainage basins. The rivers that run into the bay include the Yarra, Maribyrnong, Werribee, Patterson and Little Rivers and smaller creeks like Kananook, Mordialloc and Kororoit creeks. 

Waterways including rivers, estuaries and wetlands, play an important role in many aspects of daily life. They provide the foundation of complex ecosystems, and the region’s productivity is supported by these waterways and the resources they provide. Waterways are also strongly linked to our sense of wellbeing as places of gathering, recreation and relaxation.

Our waterways are popular recreational destinations for residents and tourists, with almost 90 million visits to our rivers and creeks each year. These waterways are also highly valued for their ecological importance, and they provide water for drinking, industry and agriculture as well as critical ecosystem services such as the processing of nutrients to keep the water clean.

The history of waterways includes a rich narrative of indigenous and European culture, lessons about the impact of urbanisation and the vulnerability of waterways, and the need to protect and improve them. 

Upper Yarra River landscape

The Yarra River. Image source: Department of Environment, Land, Water and Planning

The Yarra River

By far the largest input into Port Phillip Bay is the Yarra River. The Yarra River, known as Birrarung to the Kulin people, traditionally provided a food source and meeting place for indigenous Australians who have maintained a connection to it for over 40,000 years. It became known as the Yarra in the 1830s after a surveyor misheard local Aborigines saying Yarro Yarro, meaning ‘it flows’ or ‘ever flowing’.
The Yarra River starts in swamps just west of Mount Baw Baw. This area is within the Yarra Ranges National Park, and has been closed off to public access since 1890 to preserve water quality. This closed catchment supplies around 70% of Melbourne’s drinking water on average. The Yarra continues through forested regions before entering rural and eventually urban areas. Dights Falls marks the transition of the freshwater Yarra River to an estuary – from Dights Falls, the river continues for 17 km through Melbourne to Port Phillip Bay.

Yarra quick facts

  • Length: 242 km.
  • Runs: From 40 km east of Warburton on the flanks of Mt Baw Baw to its mouth at Newport in Port Phillip Bay.
  • Name: Yarra Yarra means ‘it flows’ or ‘ever flowing’ in the Wurundjeri language.
  • Colour: Brown in the lower reaches because of suspended silt carried downstream. This is a natural feature of the river although catchment erosion and other disturbances (such as bushfires) can make it worse.
  • Catchment: Covers about 4,000 square kilometres, includes 24 tributaries and is home to about two million people.
  • Industries: The catchment supports agriculture, forestry, recreation and tourism.
  • Home to: Unique plants and animals including platypus and the threatened Australian Grayling fish.
  • Recreation: Visitors enjoy rowing, canoeing, kayaking, fishing, cycling, walking and picnics.

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