Questions and Answers

Questions and Answers

Find key facts and commonly asked questions about the Proposal below.

Technical studies and surveys have been undertaken to inform the Environmental Impact Statement. Feedback on the detailed findings of the Environmental Impact Statement during its public exhibition is an important part of the project process.

There is a very real and substantial existing risk to life, property and community from rapid and deep flooding in the Hawkesbury-Nepean Valley after significant rainfall events.

The proposal to raise Warragamba Dam for flood mitigation, would significantly reduce risk to people’s lives and livelihoods downstream, provide more time for evacuation and reduce flood damages by 75% on average.

For more information please see the ‘Land Use in the floodplain’ fact sheet on the Infrastructure NSW website at Hawkesbury-Nepean Valley Flood Risk Management Strategy.

The Environmental Impact Statement (EIS) will include a consistency report with Australia’s obligations under the World Heritage Convention; the Australian World Heritage management principle; and the Greater Blue Mountains World Heritage Area (GBMWHA) Strategic Plan. There would be offsets proportionate to the impacts so that on balance there is no net loss to the values and improved integrity

The extent and duration of temporary inundation depends upon the size of the inflows event and the starting level of the storage at time of the event. Every flood is different, so extensive modelling of the full range of variables was undertaken. This gave a realistic representation of thousands of hypothetical flood events that were used to determine that the likely inundation

There is only one declared wild river located in the Warragamba Dam Catchment – the Kowmung River. Based on modelling, there would be no change to the level or extent of inundation for the declared section of the Kowmung River, its streams or tributaries, with the proposed wall raising. As part of the environmental assessment, the impact of temporary inundation on other rivers and streams has been analysed.

Flooding of areas upstream of Warragamba Dam happens now during significant rainfall events.

Comprehensive ecological studies have been undertaken to assess the impacts of a temporary increase in upstream inundation as a result of the proposal to raise Warragamba Dam for flood mitigation. This assessed impacts on threatened plant, animals and ecosystems and identifying measures to mitigate impacts where possible. The findings will inform the Environmental Impact Statement which will be made available for public comment.

A detailed Aboriginal Cultural Heritage Assessment has been undertaken as part of the environmental assessment process. This process has been developed in collaboration with Registered Aboriginal Parties.

The impacts on Aboriginal cultural heritage values from infrequent and temporary upstream inundation and options for minimising the impacts, will be assessed in the Environmental Impact Statement.

Registered Aboriginal Parties have participated in the field surveys, will review the Aboriginal Cultural Heritage Assessment Report, and are being consulted on the proposed options for mitigating and minimising impacts.

There are a number of ways the community has had, and will continue to have, the opportunity to provide input to the Environmental Impact Statement including:

  • directly contacting the project team by email, phone or letter to provide feedback
  • participating in the surveys for the socio-economic impact assessments
  • talking to the project team at information sessions, community workshops, briefings or community forums
  • making a formal submission to Department of Planning and Environment when the Environmental Impact Statement is on public exhibition.

Our community webpage provides a detailed breakdown of the engagement activities undertaken to date.

We invite all community members to view the Environmental Impact Statement during the display period and make a submission about what matters to them. The Department will publish all the submissions it receives online and WaterNSW will document its response to issues raised in a Submissions Report. More information about how to view and make a submission will be available closer to the display period.

To raise awareness in the community regarding the role of the environmental assessment and to engage with the community and other stakeholders at a stage when the scope of the project and environmental assessment can be influenced.

We will keep the community informed about the progress and status of our technical studies and surveys, and the timing of the public exhibition of the findings in the Environmental Impact Statement.

Early and ongoing community engagement ensures information about the proposal, and the environmental assessment process, are known so community members can have their say and provide input into the proposal.

The proposal to raise Warragamba Dam for flood mitigation will be considered under both NSW and Australian Government legislation. Construction can only begin if the environmental and planning approvals are granted and once the NSW Government has made a decision on a final business case.

WaterNSW is finalising an environmental impact statement which will be placed on public exhibition. Formal submissions can be made by any organisation or individual and submissions are encouraged. If you would like to be notified about the public exhibition period, and how to make a submission, please register for proposal updates by emailing

Importantly, the final decision on the dam raising proposal will only be made after all environmental, cultural, financial and planning assessments are complete.

Contact the Warragamba Dam Raising team:

Call: 1800 932 066


The Flood Strategy

Contact the Hawkesbury-Nepean Valley Flood Risk Management Directorate, Infrastructure NSW on:


The Flood Strategy is available online at:


Tuesday 19 October
2,426,378 ML
2,581,850 ML
9,092 ML
1,299 ML
4,444 ML
Tuesday 19 October