Dams in NSW

A dam is a barrier or structure built across a waterway to obstruct and control the flow. Dams vary in size from small earth embankments, often for farm use, to large concrete structures. Dams are built for various purposes including:

  • water supply
  • irrigation
  • hydro-electricity
  • flood control (eg retarding basins)
  • environmental controls (eg tailings storge facilities, where the aim of the dam is to impound the contents).

NSW is home to tens of thousands of dams, from small farm dams to major dams like Sydney’s Warragamba Dam.

Declared dams

Dams Safety NSW ‘declares’ dams that have a potential to endanger downstream life, cause major damage or loss to infrastructure, the environment or have major health and social impacts. Each dam is given a consequence category to reflect this potential.

According to Section 4 of the 2019 regulation this includes:

  • a dam having a dam wall that is more than 15 metres high
  • an existing or proposed dam that Dams Safety NSW is reasonably satisfied would endanger the life of a person, or result in a major or catastrophic level of severity of damage or loss were there to be a failure of the dam
  • dams that were ‘prescribed’ under the old Dams Safety Act (1978) became declared dams upon commencement of the new Act.

A dam owner must comply with the dams safety legislation once a dam is declared by Dams Safety NSW.

What structures will Dams Safety NSW declare?

Dams Safety NSW considers the following types of structure to be a dam:

  • dams
  • weirs
  • off-river storages
  • retarding basins
  • tailings dams

For more information and a list of structures that Dams Safety NSW considers not to be a dam, refer to defining dams for declaration purposes.

Although Dams Safety NSW may not consider a particular structure to be a dam for declaration purposes, owners have a responsibility to the community to address the failure risks associated with their structure. An owner of such a structure (that endangers life through releasing its contents if it fails) could consider using the principles embodied in the dams safety legislation to manage failure risk.

Declared dams map