Healthy Environment, Healthy Community, Healthy Business

Environment Protection Authority

Water Pollution

The definition of 'water pollution' in the Protection of the Environment Operations Act 1997 (POEO Act) sets out general and specific circumstances that constitute pollution. At its broadest, water pollution means introducing any matter into waters which changes the physical, chemical or biological condition of the water. It also includes placing any matter where it might fall, descend, be washed, be blown or percolates into any waters (e.g. soil which might washed into a waterway).

Additionally, the Protection of the Environment Operations (General) Regulation 2009 (see Schedule 5) includes a list of specific substances (prescribed matter) which, if they are introduced onto or into waters, are automatically assumed to constitute pollution of waters (e.g. animal matter, soil, thermal waste, any matter that contains faecal coliforms, pesticides, etc.).

It is an offence under section 120 of the POEO Act to pollute waters. However, section 121 and 122 of the POEO Act provides a defence against prosecution under section 120 where the pollution was regulated by an environment protection licence or regulation which was complied with fully.


Water pollution is often discussed in terms of its source:

Point source water pollution comes from a discrete source, such as a pipe or drain flowing from an industrial activity. Point source pollution can be critical to the health of a waterway as it occurs independently of flow conditions and can therefore impact a waterway when it has the least ability to accommodate the pollution, especially in dry conditions.

Diffuse source water pollution arises from a multitude of diverse urban and rural land uses across a catchment, rather than a discrete point source. Diffuse source water pollution is mainly driven by rainfall runoff, particularly from storms, although contamination of underground water systems and aquifers can occur over long periods independently of rainfall and may be linked to current or past land uses on the ground.

For further information on diffuse source water pollution see Diffuse source water pollution. Beachwatch also provides information on beach water quality.

Page last updated: 26 May 2015