Stormwater is any runoff from surfaces that ends up in the drains on our streets. This water flows into local creeks and can be a significant source of water pollution. How can everyone address this problem?
What is in Stormwater?
Runoff from roads, driveways, yards, roofs and footpaths makes up stormwater. This excess runoff carries leaves, litter, animal waste, car wash detergent, engine oil, fertiliser and sediment into local waterways. Large items like leaves and litter clog waterways. Sediments and oil clog the gills of animals living in the creeks. Fertilisers, animal waste and detergent can cause eutrophication, a toxic algal bloom.
In a natural environment, water infiltrates into soil and is used by plants. In cities, hard surfaces such as roads and roofs, stop water being absorbed. Traditionally, this has been channelled into drains that lead to creeks and rivers.
The most basic way of treating stormwater is a physical barrier that collects rubbish. These may be grates or netting bags at the end of pipes and/or floating barriers by stormwater outfalls. Larger rubbish is removed, but these devices do not remove sediments or dissolved pollutants.
Water Sensitive Urban Design (WSUD) improves water capture and treatment in urban areas so that local waterways receive smaller amounts of cleaner water rather than sudden rushes of highly polluted stormwater. Planners use permeable groundcovers, biofilters and rain gardens to increase infiltration and clean stormwater. A typical biofilter will incorporate a physical trap (grate or net), a sediment settling area and vegetation with drainage underneath. This three-stage process traps large solids and sediments, as well as removing dissolved pollutants. The treated stormwater can be re-used for watering public parks and ovals or be released into local waterways.
Local councils create biofilters to increase habitat and improve the quality of water flowing to local creeks and rivers (Image courtesy of Hornsby Shire Council at Hornsby.nsw.gov.au)
How You Can Help Water Quality
Responsible actions by people can make a big difference to water quality in your area. You can help by:
- Raking up leaves and bark in the gutter and placing these in the green waste bin or compost
- Putting all rubbish in the bin and picking up any you see on the street
- Cleaning up dog poo and putting this in pet waste compost or the general waste bin
- Washing your car on the lawn or in a car wash
- Not pouring paint, mop water, motor oil or anything else down the storm drain
- Using pesticides and fertilisers sparingly – a native garden will require little of these
- Build your own biofilter to model stormwater treatment using the method shown in the AusEarthEd Stormwater Treatment video.
- Create a rain garden to treat the runoff from your roof using instructions from Healthy Land & Water.
- Make a model with plastic bottles as you learn how natural areas filter water.
- Learn about sustainable ways to manage stormwater from the Australian Government.
- Water Sensitive Urban Design is summarised in this handout from Sydney Water and described in more detail by the CSIRO and water sensitive cities.