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Stormwater FAQs


Q: What is stormwater?

A: When it rains, stormwater is collected  in drains beneath the streets. These drains let the water out into rivers, creeks, lakes, wetlands and the ocean. This system differs from the natural water cycle because vast quantities of water are washed into the tunnels and straight into rivers, lakes and oceans. This water contains all the pollutants that have been picked up along the way. As water comes through the tunnels, there are no natural filtration devices to stop pollutants. To help filter out pollutants, Sydney Water installs Gross Pollutant Traps, wetlands, and creek naturalisations at key stormwater exit points in the NSW region.

When it rains some of the rainwater will hit the ground and soak into the lawn or grassy areas. But when the rain hits hard surfaces like roofs, roads and concrete driveways, it runs off downhill into drains and gets collected into stormwater pits in the side of the roads. Eventually it flows into big stormwater drains and from there into the Sydney Harbour. Along its path the stormwater picks up dust, little, sediment, heavy metals and any oils or grease that may be on the side of roads or pavements.

Q: How are organic materials (e.g. leaves and grass clippings) harmful to waterways?

A: When organic materials like leaves and clippings break down, they use up oxygen in the water and increase nutrients (particularly nitrogen) in the water. In a natural environment without stormwater drains, this does not pose a problem. However with the large volume of organic material that comes out of stormwater, much of the oxygen that aquatic plants and animals need is removed. The nutrients that the decomposed material adds to the waterways can contribute to problems such as algal blooms.

Q: How does dog poo harm waterways?

A: Dog waste harms waterways in similar ways to leaf litter (see above) but it can also contain harmful bacteria (faecal coliforms), which can make other animals and people sick.

Q: How can sand and soil harm waterways?

A: Sand and soil silt clog up the waterways and can lead to flooding in extreme cases. They also make the water cloudy, making it difficult for fish and other aquatic animals to survive. It can smother aquatic plants, such as seagrass, which are vital to aquatic ecosystems.

Q: Can't we just build more traps for litter pollution?

A: Litter traps make it possible to reduce less than 5% of the total water pollution in Leichhardt LGA. By the time litter and leaves reach the traps they are already decomposing and are able to pass through some of the devices. This material continues to release nutrients, chemicals and toxins into the water until they break down completely in the harbour or out at sea. The cost of a complete system of litter removal would also be an unsustainable burden on ratepayers.

Q: They aren't really creeks, they're drains - so why do we need to do anything?

A: Yes, at present many of our inner city creeks look like drains. However, they are the remnants of ancient ecological systems. The water they carry ends up in our harbour and on our beaches. Apart from supporting urban wildlife, these creeks flow through our communities and directly impact on our health and well being.

Q: Cigarette butts are so small, how can they be a problem?

A: Each cigarette butt contains over 4,000 chemicals, many of which are toxic to aquatic wildlife. Cigarette butts take up to 15 years to break down. Keep Australia Beautiful estimates that tens of millions of cigarette butts end up in Sydney Harbour each year.