Who Gives a Dam?
The pros and cons of raising Warragamba Dam’s walls
The Warragamba Dam is Australia’s largest urban water supply dam, with a catchment area of over 9000 square kilometres that stretch from the south of Goulbourn to north of Lithgow.
Currently, the state and the federal government are at a crossroads over a proposal to raise the dam walls.
The state government wants to raise the dam walls by about 14 metres to mitigate flood risks for houses and residents on the floodplains downstream.
However, the federal government, Blue Mountains City Council and UNESCO have condemned the dam raising proposals as it poses a risk to inundating Indigenous cultural sites and other natural sites of significance upstream.
The Warragamba Dam serves not only as Sydney’s primary water supply, but also helps to mitigate flood risks for communities downstream.
The affected areas include the Hawkesbury Nepean floodplain, where over 130,000 people live, trade and work.
WaterNSW and Infrastructure NSW, operating within the NSW government, are currently working with consulting companies to assess the feasibility of raising the dam walls by 14 metres.
The raised Warragamba Dam wall would mitigate floods by creating an air gap to capture and temporarily hold back floodwaters if the dam reaches full water supply level.
The raising of the Warragamba Dam poses a risk for significant natural and cultural sites upstream when floodwaters inundate Burragorang River.
Raising the wall would potentially allow flooding of up to 4,700 hectares of land and 65 km of wilderness rivers and streams.
The proposal for raising the dam will also pose risks for threatened plants and animals in the Greater Blue Mountains World Heritage Area.
UNESCO, the federal government and the Blue Mountains City Council are just some of the organisations that have condemned the proposal to raise the dam walls.
Warragamba Dam at around 55% capacity in mid-2019
Warragamba Dam 1 year later at full capacity in mid-2020
A Brief History of the Warragamba Dam
Constructed between 1948 to 1960, the Warragamba Dam is Sydney’s largest water supply dam, holding about four times more water than Sydney Harbour. It is located in Warragamba, an hour drive’s west of the Sydney CBD, and supplies 80% of Sydney’s water resources.
The Warragamba River was an ideal location as it offered a large catchment area and a river flowing through a narrow gorge. The location was first suggested in 1845, however it wasn’t until a century later that construction started off the back of Sydney’s worst drought in recorded history, from 1934 to 1942, and the population boom after World War 1.
In February 2020, Warragamba Dam capacity was recorded at 42.7%, which prompted the NSW Government to declare level 2 water restrictions. Although the water levels were low, the lowest recorded level was at 32.5% capacity on 8 February 2007, which prompted level 3 water restrictions.
However, due to heavy rainfall in August, the Warragamba Dam reached full capacity on August 16 2020. The last time the dam was full and spilling was in July 2016.
However, raising the dam walls is not an unprecedented move.
The dam has always attracted debate around flood mitigation versus nature conservation over the past few decades. In the early 1990’s, the Liberal government created a detailed proposal to raise the dam by 23 metres.
“There was a very extensive environmental impact statement that was done at that time that took seven years to complete,” said Cr Zamprogno.
“That study was ratified by three different international and independent experts. They looked at a number of different strategies, not merely raising the dam, but also looking at things like operating Warragamba Dam differently.
“They came to the conclusion that raising Warragamba Dam wall was the best and safest way to mitigate against floods.”
However in 1995, under Bob Carr’s Labor government, the planned $280 million wall raising was cancelled. Following on from the cancellation, leaked government documents revealed that the alternative flood mitigation method, a $98 million spillway, would divert more water at greater speed.
Some criticised the government for not devising a comprehensive alternative flood-management strategy for the river’s increasingly urbanised floodplain.
The auxiliary spillway, which provides protection for the integrity of the dam but no protection for the people downstream, operates in the event of a flood with one chance in 750 of it happening in any year. If the auxiliary spillway ever operates it will release an enormous amount of water downstream, travelling with velocity and force that would severely affect more than 100,000 residents in Western Sydney.
In a Hansard recorded in the NSW Legislative Assembly on 1st May 2018, Kevin Conolly, Member for Riverstone, said, “There is no option that would see zero environmental impact when that amount of rainfall occurs. The raised wall would only alter the location of the impact that would inevitably occur.
“By reducing the downstream peak, the higher wall would reduce the damage to homes and businesses, as well as to schools, public buildings sewerage and electricity assets, railways and roads. Most importantly, the raised wall would save lives by reducing the peak of a flood downstream and increasing the time available for evacuation of areas likely to be inundated.”
Flooding of Indigenous cultural sites and natural habitats is a large concern of the critics against the wall raising, however Cr Zamprogno suggests the majority of these concerns stem from misinformation.
“So when it is said that there are threatened ecological communities, threatened Aboriginal cultural sites and so forth, then it’s good to actually look at the data,” said Cr Zamprogno.
“So if the dam wall was raised, then that would cause inundation to approximately 0.04 to 0.05% of the World Heritage Area. It’s a very, very small area of the total amount.
“Nobody disputes the existence of World Heritage level ecology above Warragamba Dam in the Burragorang catchment. But that has to be balanced with ecological communities and indeed the human habitation that exists below Warragamba Dam.”
There is a risk that raising the Warragamba Dam wall may result in the de-listing of the Greater Blue Mountains from the UNESCO World Heritage List due to the impact on the values for which the park was listed.
This interactive map shows the area of which flooding will occur if the water levels increase by 5 metres.
A vocal advocate against the wall raising is Harry Burkitt, campaign manager for Colong Foundation for Wilderness. He has worked alongside various organisations to put pressure on the NSW government to scrap the proposal.
Harry Burkitt, Campaign Manager for Colong Foundation for Wilderness
The other reason against raising the wall is the concern over the assessment of cultural heritage and environment upstream.
The NSW government has contracted the Snowy Mountains Engineering Corporation (SMEC) to assess the environmental impact upstream if the walls were to be raised.
However, in one of the submissions to the Select Committee on the Proposal to Raise the Warragamba Dam wall, the submission outlined the lack of consultation with the Blue Mountains Traditional Owners by SMEC.
The submission said, “When Traditional Owners invited SMEC and WaterNSW to attend a public meeting to discuss their concerns last month, they simply didn’t show up.
“Even when SMEC Engineering held their first consultation meeting about Warragamba Dam wall raising project in 2018, Traditional Owners were given just four days’ warning by SMEC of a consultation meeting being held in northern Sydney.”
In 2017 the World Bank imposed sanctions on SMEC after an investigation into corporate misconduct in south Asia. The sanctions have since been lifted.
“These guys have been putting wrecking balls through Indigenous culture for 30 years with major dam projects,” said Mr Burkitt.
“These tribal people who have been living in the forest of South-east Asia knew SMEC. They said when SMEC came along to interview them about this dam project that they were doing the assessment for, they turned up with the local government and a tank. These are the people that the NSW government see fit to talk to the traditional owners of the Blue Mountains and the Burragorang Valley, whose hundreds of their sites they want to destroy. They see fit to put SMEC in charge.”
Where to from here?
Currently, the NSW government is still assessing the environmental impacts that the wall raising may have on the river upstream.
The findings from the assessments will result in an Environmental Impact Statement (EIS) which was due in 2019 for public exhibition.
The EIS will significantly affect the business case for or against the wall raising as it covers key issues such as assessing the impact on biodiversity and World Heritage properties upstream of Warragamba Dam.
However, the sophisticated nature of the assessment has delayed the publication of the EIS as the state government continues to work with external consulting companies.
“There’s no agency involved with this project who has not expressed extreme, extreme objection to the way the assessment has been undertaken both on Aboriginal cultural heritage and the environment upstream,” said Mr Burkitt.
“We have the federal government saying that they will not support this dam unless the Aboriginal people of the Blue Mountains give free prior and informed consent. I mean, that’s not gonna happen, that’s never gonna happen, and they know that the assessment’s that’s been done by the state government is really a con job by a consultancy in SMEC engineering who has gone around screwing around Indigenous tribes all around the world for the last 30 years.”
“Of course we all want to protect lives on the floodplain,” said Mr Burkitt.
“There’s been a whole lot of people that have been put there that shouldn’t have been put there but are there now and we got to protect them somehow, and in some cases, we’ve actually got to look at taking some of those people off the floodplain because it’s just too dangerous to have them there.
“And look, we all want to protect people and manage the flood risk, but it’s not a single bullet solution that it’s being made out to be. There’s a whole range of management measures that need to be implemented if we are to mitigate that risk in the valley to life.”
Although critics of the proposal to raise the walls have been very vocal, Cr Zamprogno noted that a large number of opponents to the project were people who did not live on the floodplain.
Cr Nathan Zamprogno
WaterNSW and the Blue Mountains City Council were reached for comment.
– Calvin Lu