Fresh water runs into Sydney Harbour from the Parramatta River and Lane Cove River and from rain collected in stormwater drains. Keeping these water sources clean and free of rubbish is known as catchment management and is an important step in maintaining a healthy harbour.
What is a Catchment?
A catchment is an area of land in which rainwater collects. Rainwater flows into creeks, streams and rivers and moves towards the lowest point of the catchment.
Catchment areas are decided by the shape of the land. If rainwater falls on one side of a hill it may enter a different catchment area than it would if it had fallen on the other side of the hill, or it could enter the same catchment area if the land directs it that way.
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Catchment Management
Catchment management is a way of managing land areas based on how water flows. Catchment management is based on the understanding that if something reduces water quality high in the catchment, water users lower in the catchment will feel the impact. Water users means all the plants, animals, fish and people.
Catchment management involves everyone and every organisation in the catchment. This includes homeowners, schools, businesses, industry, farmers and government organisations such as local councils. We all have a responsibility to reduce our impacts on water quality so that plants, animals and other people in the catchment have access to good quality water.
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The Sydney Harbour Catchment
The Sydney Harbour Catchment covers an area of 530 square km and includes the waters of Port Jackson (Sydney Harbour) and Middle Harbour. The main rivers feeding into Sydney Harbour are the Parramatta River and the Lane Cove River but there are many streams and creeks that also feed into the harbour.
The Sydney Harbour Catchment area has been heavily developed. There are more than 1.2 million people living in the catchment, which includes the cities of Sydney and Parramatta. Only 62 square km remains undeveloped and some of this land is protected in Lane Cove, Garigal and Sydney Harbour National Parks. This land provides a valuable home for plants and animals.
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Catchment Issues
As we have seen all rain that falls in a catchment makes its way to the creeks and streams and eventually to the lowest point of the catchment, in this case Sydney Harbour.
When rain falls high in a catchment that has not been developed the plants, trees and soil slow the water down. This action protects the lower areas of the catchment from flash floods. This sort of protection is known as an ecosystem service and shows the importance of not developing all natural areas.
As the water travels it passes through environments that have been disturbed by people such as land that has been cleared for farming or to build houses and factories. During this journey the water picks up different types of pollution and carries them to the harbour.
When rain falls on a farmer's field it can wash away chemicals that the farmer has put onto the fields to help the crops grow or to kill pests. When the chemicals get washed into creeks and streams the water becomes polluted and the chemicals upset the creatures that live there.
When rain falls onto land that has been concreted over such as streets, shopping malls, house driveways and factories it cannot soak into the earth and there are not many trees and plants to slow it down. This rain goes into stormwater drains, which direct it into streams, creeks and the harbour. This water picks up pollution from the concreted areas and washes it into the waterways. These pollutions include oil and fuel from cars that has been spilt onto roads and litter such as plastic bags and cigarette butts.
Once in the harbour the pollution makes a real mess. All the oils, fuels and greases float on the water surface where they block sunlight and smother wildlife. All the rubbish, especially plastics, is dangerous to animals that mistake it for food or get tangled in it. Some rubbish washes up onto beaches and looks ugly when we want to swim or play on the beach. Some of the pollution sinks to the harbour bottom where it smothers plants and animals.
So you can see we all have to be careful what we do in the Sydney Harbour Catchment. Anything we drop or throw away and even things we intentionally put on our streets, gardens and parks can be washed into Sydney Harbour.
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