In Cairns there are more than 260 drains and waterways whose water flows to the ocean, and the Great Barrier Reef. The water that is transported through these drains and waterways is called stormwater. Stormwater is water that has drained off a site from the rain that falls on the roof or other impervious surfaces such as the driveway, footpath and road. With this water many pollutants are carried with it. Everything that goes into the drains will end up in our ocean.
THIS WATER IS NOT TREATED.
Image courtesy of Tangaroa Blue – www.tangaroablue.org
Litter and Marine Debris- plastic, plastic bags, cans, food wrappers
Marine debris are man-made items that ended up in the marine environment through littering or dumping. Stormwater drains are able to carry items of litter out to the ocean, and if these are made of plastic they may remain in the environment, for tens, hundreds or even thousands of years. Plastics are not only a choking hazard for marine life but it may clog up the digestive systems of marine animals, and have found to be a serious threat for seabirds too. Plastics may then break down into micro-plastics, and the effects of these are also poorly understood, although coral has been found to ingest these micro-plastics as it feeds indiscriminately. Plastics may also be carried by currents to ocean gyres, huge areas of rubbish-filled ocean where currents meet and slowly spiral.
On every beach around Australia you will find some form of marine debris, from rubbish swept down stormwater drains, to litter left by visitors and international debris washed up by the ocean. The Australian Marine Debris Initiative (AMDI) is a national network of over 40,000 volunteers and partners, coordinated by Tangaroa Blue Foundation, focused on reducing the amount of marine debris washing into our oceans. You can find out more about how they do this here.
Natural Pollution – sedimentation (leaf litter, soils, garden clippings), nutrient rich (fertilisers, animal faeces)
Sedimentation is composed of the small particles that are washed down stormwater drains. These can come from a range of sources such as organic matter (leaf litter and grass) eroded soil structures, and the weathering of infrastructure such as paths, buildings and roads. When it reaches the ocean, sediment causes turbidity, or muddiness of the water and this can pose a number of threats to complex marine systems. Light is an important factor for the growth and survival of coral reefs. Small sediment particles have the ability to block the light coral needs to survive, to smother the coral and to even cause mechanical abrasions.
Nutrients that stormwater drains introduces to the reef are typically in the form fertilisers or organic matter such as vegetation and dog faeces. These are high in nitrogen and may also contain phosphorous, both of which are able to cause excessive growth of aquatic plants such algae, and may cause devastating algal blooms. Algal blooms are able to block light, and to use much of the available dissolved oxygen, having devastating effects on marine ecosystems.
Chemical Pollution – pesticides oil, grease, detergents, soaps
A number of chemicals may use the storm water system as transportation into the ocean or the Great Barrier Reef. These may be sourced from detergents (from car washing), oils and lubricants from vehicles, herbicides and pesticides used in the garden, and the weathering of roofing systems and concrete. Unfortunately all of the effects of these in the chemicals, especially in combination, are not totally understood. However some are known to be highly toxic to marine life, and others to contain heavy metals that can persist within the environment for long periods of time.
Cairns Stormwater System
In the central area of Cairns alone, there are 20,000m of culverts, 58,000m of open drains, 168,500 m of pipes and 3,800m of waterways. The drainage network is a combination of pits, pipes, open channels and natural waterways which is continually developed, managed and maintained. These carry stormwater into creeks, rivers and other catchments. The stormwater eventually ends up in the ocean. As stormwater is not treated, everyone has a role to play in keeping pollutants out of the stormwater system to ensure the long-term health of our rivers, creeks and oceans. Find out more here.
Cairns Wastewater Treatment
When it has made the transition from drinking water to sewage, Cairns town water ends up at the Marlin Coast waste water treatment plant, which operates a bio-nutrient reduction system. Here, it is transformed from sewage, by an activated sludge process, into ‘A’ grade recycled water and a small amount of solid waste. The water is supplied to a local school and golf course for irrigation, and the remainder flows to Moon Creek and into the Coral Sea. Read more here.
1. Sweep dirt, leaves and rubbish from driveways, sidewalks and pathways rather than hosing them down the drain.
2. Compost green waste
3. Vegetate bare areas in the garden
4. Never throw rubbish down the stormwater drains, or in creeks and rivers
5. Avoid using fertilisers, pesticides and herbicides. If they need to be used, reduce the chance of run-off into the stormwater system by not using too much and not applying them before rain is expected.
6. Wash the car on the grass instead of on the driveway, and limit the use of cleaning products
7. Check the car for leaks and recycle or safely contain motor oil
8. Pick up after your pet, using a recyclable bag and put it into a rubbish bin
The Marine Response Team want to reduce stormwater pollution by…
Getting more people involved – communities and school groups
Encouraging you to educate your friends and families about the positive actions they can make
Raising awareness in the wider community by using stencilled drains