Adelaide River dams recommendation accepted by Gunner Government as part of $1.45b plan

Adelaide River dams recommendation quietly accepted by Gunner Government as part of massive $1.45b plan

by | Mar 23, 2022 | News | 0 comments

The Gunner Government has quietly accepted the findings of a report that recommends building two off-stream dams with half the capacity of Sydney Habour along the Adelaide River, coupled with recommissioning Manton Dam, as the best way to supply Darwin with water long term, which could cost an estimated $1.45 billion.

Infrastructure Minister Eva Lawler made somewhat of a non-announcement announcement in the eleventh paragraph of a joint media release on February 1, below comments by Deputy Prime Minister Barnaby Joyce, but did not mention the $1.45 billion cost, nor use the word ‘dam’.

Ms Lawler gave no indication of what specific action the government would be taking on the proposal, whether they were seeking money from the federal government, and did not provide a timeframe for when the Adelaide River dams would potentially be built – normal details provided in an announcement of such significance.

“A safer, more reliable and more sustainable water supply in the Darwin region is a step closer with the completion of the Adelaide River Off-Stream Water Storage (AROWS) detailed business case,” the press release began.

Yesterday, in a new statement, she said Power and Water had done significant preliminary work around the design and delivery of the project.

In a released detailed business case, the Department of Industry, Tourism and Trade said of the two preferred options investigated, the two-dam option was the only one that was financially viable, and would provide an additional 67 Gigalitres per year at a cost of $1,686 per megalitre, which would supply urban, agricultural and industrial uses.

The report said despite the $1.45 billion infrastructure cost, the plan had a positive benefit-to-cost ratio, and would not stop the flow of the Adelaide River, relying instead on two main dam structures at low points to secure water within the proposed basin.

It also said the plan would have an annual operating cost of $34.8 million, and would enable an expansion of industry at Middle Arm and development of irrigated agriculture at Lambells Lagoon.

Water extraction from the Adelaide River would only occur during the wettest months,” the report stated. “There is no extraction during the remaining months of the year.

It said water would be treated at the proposed Strauss water treatment plant prior to distribution to customers, with the two main dams and two secondary “saddle dams” holding about 250Gl of water (Sydney Harbour holds about 500Gl) and supply about 60Gl, with a development time of seven to 10 years.

The report estimated it would almost double the water supply capacity of Darwin River Dam, and as the climate continues to change, it would provide a secure and reliable source of water to the Darwin region.

The report also said it would be unlikely to impact on fishing accessibility for the Adelaide River.

A further 7.3Gl would be produced by recommissioning Manton River Dam, with a development time of three to four years.

The second, non-preferred option, relied on various sources of water, including a desalination plant that would provide water only for industry.

The report said that option would cost $633 million, and supply 17Gl at a cost of $4,738 per megalitre, but the benefits would not outweigh the costs.

Pew Charitable Trusts spokesman Mitch Hart said that despite the branding, it was a dam being built, and there needed to be a ban on floodplain harvesting.
“More water is going to be taken, more water is going to stored, more water diverted from its natural flow. Territorians can know a dam when they see one,” he said.

“Territorians are rightly worried about any attempts from the government to take significantly more water from the floodplains that power the Adelaide River, home to the jumping crocs, cultural connections and great barramundi fishing.

 

“We’ve now seen a business case outlining which large water-thirsty industries stand to benefit from this project.

“There is a better pathway for the Gunner Government to pursue across this and other catchments – one that resolves the huge gap between what communities and scientists know is needed to maintain and improve the health of our river systems and what government and water-thirsty industries are pushing.
“We need to recognise that our rivers and floodplains are connected and listen to the communities on the ground, not put forward dam proposals with the aim of getting federal buckets of money for large-scale cotton and gas.”

In Tuesday’s press release, Ms Lawler announced a recommissioned Manton Dam to supply public drinking water would continue to support boating and fishing, requiring Power and Water to find a way to treat the water after it left the dam.

She said it was the critical first stage of supplying water to Darwin, with the Adelaide River dams forming the second stage.

Ms Lawler did not provide a cost, nor how much it would cost to recommission Manton, or whether the government was seeking funding from the Federal Government for both stages.

“Securing a safer, more reliable and more sustainable water supply for Darwin is essential for the region’s future growth and economic prosperity,” she said.

“It is important that we develop sustainable solutions that protect our environment and maintain our great Territory lifestyle.

“Manton Dam RTS [return to service] and AROWS [Adelaide River off-stream water storage] are an economically viable solution to provide water security to the Darwin region for the next 50 years and beyond.

“Power and Water Corporation had identified AROWS as the preferred water source in its Darwin region water supply strategy and has already undertaken significant preliminary work to inform the design and delivery of the project.”

She said the NT Government was working with Power and Water to progress development for both projects, which for Manton Dam included detailed design of the infrastructure components, further stakeholder engagement and assessment of the environmental and social impacts of the project.

The Adelaide River component meanwhile included a water allocation plan for the Adelaide River catchment, an environmental impact assessment, stakeholder engagement and community consultation, and concept design of the infrastructure components.

Power and Water recently released an expression of interest tender for Stage 1 of the design and construction of the Manton Dam project, Ms Lawler said.

CLICK here to see the detailed business case report for both water supply options.

Editor’s note: This story was updated to remove a reference to media not picking up on the original government announcement about the proposed dams. The NT Independent regrets the error.

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