Environmental issues

Water quality

What is urban Stormwater?

The drain is just for rain.
why are words being stencilled on the grate of my drain?

Stormwater is pure rainwater plus anything the rain carries along with it. In urban areas, rain that falls on the roof of your house, or collects on paved areas like driveways, roads and footpaths is carried away through a system of pipes that is separate from the sewerage system. Unlike sewage, stormwater is not treated. In some cases it's filtered through traps, usually located at the end of the pipe system, but it still flows directly from streets and gutters into our rivers, the harbour and the ocean. Straight from your street to waterways inhabited by fish, frogs and other aquatic animals and plants.

If you live near a waterway or often spend time in or near the water you are probably familiar with what happens after rain. Polluted stormwater spreading out into the surrounding clean water can be clearly seen because it's a muddy colour, and often carries litter with it. You may be advised not to swim for a couple of days, because the pollution carried along with the rainwater may pose a significant health risk.

Stormwater pollution can be controlled if everyone plays a part in managing the drains in the streets where they live and work. In other words, if you look after your local drains, you can dramatically improve what happens in the harbours, on the beaches and in the rivers. The most effective way to reduce stormwater pollution is to stop it entering the system in the first place.

Do you know where the water goes?

Know where it all goes.



What happens to the water that runs off your roof?

What happens to the water that runs off your driveway, or escapes from garden beds?

Where does the water go when it goes down the drain?

Click the image for a larger view

Pollution traps

There are various types of stormwater pollution traps, but they all act like filters. They catch pollution before it has a chance to enter the waterways. They have to be cleaned or emptied regularly, and their contents are carried away to landfill. Types of pollution traps include:

  • artificial wetlands
  • oil and litter booms
  • gross pollutant traps
  • trash racks
  • sediment traps.

The most effective way to reduce this problem is to prevent pollution entering the stormwater system in the first place. The traps don't catch all the silt or litter, and they don't stop chemicals.

Page last updated: 07 May 2018