Study Session 4  Water Pollution

4.3.5  Urban surface water run-off

Rainwater that runs off road surfaces, roofs, parking areas, etc. carries with it a variety of components (Table 4.1). The bulk of the contaminants can be traced to motor vehicles. Surface water run-off can cause damage to streams, rivers and lakes by degrading the water quality and harming aquatic life. The pollutants present can hinder the growth and reproduction of fish and other creatures, and affect photosynthetic activity. Plant nutrients may contribute to eutrophication.

Table 4.1  Pollutants that may be present in rainwater run-off.

Pollutant Likely sources
Sediment Construction, road surfaces, emissions from vehicles, industrial sources, vehicle wear
Copper Vehicle brake pads, industrial activities, plumbing and guttering
Lead Industrial activities and residues from historical activities (plumbing, paint, leaded petrol, sprays), tyre-balancing weights, vehicle brake pads
Zinc Vehicle tyres, galvanised building materials, paint, industrial activities
Hydrocarbons Vehicle emissions, lubricating oils
Rubber Tyre wear
Detergents Wash-down areas, domestic discharges (e.g. from car washing), industrial discharges
Litter Discarded material (e.g. plastic bags, cups, cigarette ends), windblown materials, illegal dumping