The term stormwater refers to precipitation that does not infiltrate the soil due to impervious surfaces, such as buildings, pavements and roads. Instead the water drains into sewers or directly into waterways. Where stormwater drains into sewer systems the water is treated along with the other sewage before release into the environment (See: Sewage treatment). Where stormwater drains into waterways it is a major non-point source of water pollution. It can carry pollutants from a wide variety of sources including but not limited to: debris (e.g. plastic bags, bottles and cigarette butts), sediment, pesticides, herbicides, fertilisers, paint, solvents, oils, grease and pathogens.
The direct impacts of stormwater runoff directly into waterways may include:
- Increased water nutrient concentrations
- Increased water faecal contamination
- Increased water sediment load
- Increased water chemical contamination
- Increased plant detritus in water
- Increased debris in waterways, e.g. plastic bags – debris can choke, suffocate or disable aquatic life such as ducks, fish, turtles and birds.
Last updated 7 September 2010