Parramatta River Estuary
The Parramatta River Estuary is a significant and biodiverse estuary located on the east coast of Australia, serving as the main tributary to Sydney Harbour and Port Jackson. Stretching approximately twelve miles from its tidal limit in Parramatta to its confluence with the harbour, the estuary is rooted in rich Aboriginal history, with its name translating to "the place where the eels lie down." Despite its ecological importance, the estuary faces threats from urban development, contamination, and habitat degradation. Extensive industrialization and changes in land use over the past two centuries have led to the loss of natural vegetation and the alteration of creek courses, impacting the local wildlife.
The estuary supports a range of habitats, including mangroves that are vital for aquatic species and water quality. However, significant human activity has resulted in heavy contamination of sediments, prompting a ban on commercial fishing due to health risks. Environmental monitoring and remediation efforts are ongoing, reflecting the community's commitment to restoring the estuary's health. The area is also crucial for recreational activities and serves as a habitat for various bird species, particularly migratory waders, with international agreements in place to protect these birds. Climate change poses an additional challenge, with recent events highlighting its impact on local ecosystems.
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Parramatta River Estuary
- Category: Marine and Oceanic Biomes.
- Geographic Location: Australia.
- Summary: This heavily modified but biodiverse estuary on the east coast of Australia is threatened by urban development and contamination.
The Parramatta River forms one of Australia’s most iconic estuaries; it is the main tributary to Sydney Harbor and Port Jackson. In geological terms, Port Jackson is a specific type of estuary called a ria. The word ria refers to an unglaciated river valley partly flooded by rising sea levels.
The river begins at the confluence of two smaller rivers just west of the city of Parramatta. An Aboriginal name, Parramatta stems from the word baramada or burramatta, and is commonly translated as the place where the eels lie down. Parramatta is the second-oldest settlement in Australia, established in 1788; today, it is an important city within greater Sydney. The estuary begins at the tidal limit, a weir in central Parramatta, and extends in an easterly direction for about twelve miles (nineteen kilometers) to an imaginary line between headlands at Yurulbin and Manns Point. Beyond this point, the estuary merges into Sydney Harbour. The total catchment of the river is approximately fifty square miles (130 square kilometers).
The Parramatta River estuary and Sydney Harbor form a large waterway that literally cuts Sydney in half. As a result, the many crossings and the regular ferries, called river cats, that stop at public wharves along the river are extremely important for transport and navigation in and around the area.
Biodiversity
The catchment supports a broad range of wildlife in diverse habitats, including bushland, rivers, creeks, and wetlands. The estuary itself supports diverse assemblages of aquatic plants and animals, including large areas of mangroves that form important spawning grounds, shelter, and feeding zones for fish and crustaceans. They also provide large amounts of organic matter for the base of the food web. Mangroves also help maintain water quality by filtering silt from runoff and recycling nutrients.
At the time of British colonization, mangroves were far fewer, but urban development has since allowed soil to be washed into the river, causing siltation in many bays and providing suitable conditions for mangroves. Between the 1980s and 2000s, the extent of mangroves increased by 25 percent. By contrast, large areas of seagrass were lost.
Eel, carp, long-necked turtles, and small mammals such as the ring-tailed and brush-tailed possum are common sights. Birds found in the Parramatta River Estuary biome include the yellow-tufted honeyeater and the white-napped honeyeater, both often seen near the upper portions of the river. The estuary also provides a habitat for the endangered nocturnal marsupial, the long-nosed bandicoot.
Effects of Human Activity
Over the past 200 years, extensive urban development along the river has meant that much of the natural vegetation has been removed. The original courses of creeks have also been altered, with many now canalized or straightened and lined with concrete. Large areas of agricultural land have been transferred to residential or commercial use. Land claim has occurred along many areas of the river, particularly at the heads of bays. The areas were often used as rubbish dumps before being converted to playing fields or large parks. Large amounts of shoreline are now protected by artificial seawalls.
Much of the foreshore still belongs to businesses or private residences, but an increasing amount of waterfront land is becoming available to the public as foreshore reserves. The estuary is important for recreational activities, and especially vital in its role of hosting nature reserves.
Approximately one million people live within the catchment area, and consequently, the area is under intense pressure from urban development. Researchers at the University of Sydney have shown that estuarine sediments in the Parramatta are heavily contaminated; this condition is worse on the southern side of the river because that is where industrial development was greatest. Many of the contaminants, such as dioxins, lead, DDT, and polycyclic aromatic hydrocarbons, originated in chemical and paint factories here. Some areas have been remediated to remove contaminated sediment, or have been covered with concrete to prevent contaminants from being disturbed and incorporated into the food web.
In 2006, commercial fishing was banned throughout Sydney Harbor, including the Parramatta River, because of contaminated sediments in the river. Water quality in some areas of the estuary is monitored by the State Department of Environment and Climate Change for bacterial contamination. The water quality is generally acceptable except after heavy rains, when large volumes of water cause sewers to overflow, contaminating the estuary with waste, bacteria, and nutrients. Runoff from the land also transports litter, nutrients, and toxic chemicals into the estuarine waters and sediments, hindering wildlife health and undermining habitats.
The Parramatta estuary has several areas of wetlands, such as Bicentennial Park and Newington Wetlands, that are of national importance for birds, particularly migratory waders. Agreements exist with China and Japan that require each country to take measures for the management and protection of shared migratory bird species and their environments.
Global warming and climate change have negatively impacted the Parramatta River. Experts believe that strong storms and elevated water temperatures resulting from climate change reduced the oxygen in the water and caused the deaths of thousands of fish in 2022.
Bibliography
Blaxell, Gregory. The River: Sydney Cove to Parramatta. Halstead Press, 2010.
Cardno Lawson Treloar Pty. Ltd. "Parramatta River Estuary Data Compilation and Review Study." Department of Environment and Climate Change, July 2008, www.ourlivingriver.com.au/content/uploads/2018/08/Parramatta-River-Estuary-Data-Compilation-and-Review-Study.pdf. Accessed 31 Oct. 2024.
Cole, Joyce. Parramatta River Notebook. Kangaroo Press, 1983.
Cox, Lisa. "Parramatta River Fish Kill Investigated after Thousands Found Dead along Riverbanks." The Guardian, 8 Feb. 2022, www.theguardian.com/environment/2022/feb/09/parramatta-river-fish-kill-investigated-after-thousands-found-dead-along-riverbanks. Accessed 31 Oct. 2024.