Stormwater is rain that runs off urban areas into drains that carry it into natural waterways such as rivers, creeks and the sea. Every year about 86,000 million litres of stormwater flows from the greater Adelaide urban area through drains, creeks and rivers into Gulf St Vincent.
In 2013 around 100,000 ML flowed from the Adelaide and Mount Lofty Ranges region to the sea. It’s important that some of this water flows through creeks and rivers to the ocean to maintain passage for our native fish.
Stormwater can contain many kinds of pollutants that it collects as it travels over land, including oil, grease, fertilisers, litter and heavy metals. Once stormwater enters waterways, these pollutants can adversely impact water quality and the ecosystems reliant on it. Some pollutants poison the fish, animals, insects and plants that live in and rely on these waterways. Other pollutants, such as nutrients, are present in such great quantities that they cause the excessive growth of unwanted plants that impact natural waterways and the marine environment.
Common pollutants found in stormwater include:
- oil, grease, fuel and metals from vehicles onto the road
- rubber from car tyres
- chemicals and paints that are not disposed of properly
- excess pesticides and fertilisers
- grass clippings and high loads of leaf litter in autumn from non-native trees are harmful due to high nitrogen content
The type and volume of stormwater pollution is influenced by:
- when it last rained
- intensity of the rain
- building density and other land uses in the catchment
- amount of vegetation cover
- the cleanliness of the streets
- local practices such as street sweeping, pet control and excessive garden watering.
Reducing stormwater pollution
There are a number of methods Natural Resources Adelaide and Mt Lofty Ranges (AMLR) uses to reduce stormwater pollution.
- Gross pollutant traps catch materials using nets, trash racks, floating booms or baskets in drains. Natural Resources AMLR maintains 25 traps across Adelaide, with the cost of removing debris at up to $600 per tonne. Captured organic material is sent for composting and the rest recycled where possible.
- Sedimentation basins are constructed on creeks to trap and so reduce sediment levels.
- Wetlands are constructed to improve water quality and harvest stormwater for use. Combined with gross pollutant traps and sediment basins, these wetlands are a very efficient means of reducing sediments, nutrients and other pollutants.
- Stormwater use, where harvested water is diverted to irrigate parks, ovals and gardens, further reducing the flow of pollutants into creeks and the ocean. This use also reduces pressure on Adelaide’s drinking water supply.
- Monitoring initiatives help to determine if there is litter that needs to be removed or reported to local councils. Fortnightly monitoring is conducted along the River Torrens and other waterways.
Stormwater strategy report
2011 Regional report card for stormwater and waste water use
2010 Regional report card for stormwater and waste water use