NT dam brought back to service to ensure intermittent water security

Demand for water in the Darwin region is expected to double by 2050 and, with water storage levels in Darwin River Dam becoming increasingly impacted by climate change and evaporation, a decommissioned dam is being brought back to life to help maintain water security.

While the proposed Adelaide River Off-stream Water Storage project (AROWS) is set to ensure water security for the Darwin region for years to come, Manton Dam will be tapped to provide extra drinking water supply in the interim.
 
Built in the 1940s with a storage capacity of 14,000 ML, Manton Dam was once Darwin's primary source of water until the Darwin River Dam was commissioned in 1972. Last month, the NT Government awarded a major construction tender for the Manton Dam Return to Service project, which is part of Stage 1 of the Darwin Region Water Supply Program.
 
Set to be delivered by the NT Government and Power and Water Corporation, in partnership with the Australian Government’s National Water Grid, the Manton Dam Return to Service represents a $190 million investment in water security for the region.
 
The Australian Government is contributing $300.6 million through the National Water Grid Fund to the first stage of the Darwin Region Water Supply Infrastructure Program – Stage 1.
 
When the project is complete, Manton Dam will provide an additional 7300 ML a year into the Darwin region water supply system to provide immediate water security, and to support future economic development in future.

The project is expected to be completed in the second half of 2026 and will include:

• an upgrade to the existing intake tower and the construction of a new 20ML per day pump station;
• a 22km pipeline from Manton to Strauss, and;
•  construction of a new 20ML per day water treatment plant at Strauss.

Power and Water has completed planning and approvals processes to prepare the project, including the environmental referral through the Northern Territory Environment Protection Authority.

Power and Water Executive General Manager Water Services Stephen Vlahovic said the utility is committed to delivering secure, reliable, and cost-effective drinking water for Territorians, now and into the future.

“Power and Water is looking forward to working with Exact Contracting Pty Ltd to deliver this major water infrastructure project,” he said.
 
“Their successful tender submission met both the technical requirements of the project and incorporates a significant number of local businesses to deliver the works and was assessed as providing best value for the Territory."

Ensuring water security

Power and Water Corporation Manager Asset Delivery David Rossi said the Darwin region is one of the highest consumers of water per capita in Australia, and the move to recoup Manton Dam as a drinking water source is necessary to ensure the region is appropriately supplied over the coming years.

“Power and Water Corporation has maintained the dam since it was established in the event that this water storage might need to be accessed again,” he said.
 
“It was decommissioned due to its age, and a few other factors, including the cost of producing water from the dam, which was a lot more expensive than the cost of producing drinking water from the newer Darwin River Dam.
 
“But we are now in a position where we are currently at our limit in terms of our reserves in the Darwin River Dam. It’s not just about keeping a certain volume of water for consumption, it's also about keeping adequate reserves. Consequently, we have been looking at developing other water sources.”
 
While AROWS is earmarked as a new water source for the Darwin region, Rossi said it will be a few years before that scheme comes online, and Manton Dam will provide an interim water source to assist.
 
“Over the years, there have been a few ideas on how to access the water from Manton Dam. There has been a proposal to cut a channel between Manton dam and Darwin River Dam, with the water flowing from Manton to Darwin. That never went ahead,” he said.
 
“Now that there is funding from the Federal Government through the National Water Grid, Power and Water Corporation has taken the opportunity to develop the project further as an interim measure to improve our water security requirements.”

Maintaining recreation

Since being decommissioned, Manton Dam has been used for recreational purposes. Rossi said a lot of work has been involved in the planning to ensure the dam can continue to be a recreational resource for the Darwin community.
 
“We have been working on this project since 2008. That’s typical for these types of water sourcing projects because time needs to be taken to do environmental impact studies, potential water quality issues at different levels in the dam,” he said.
 
“We have been working with Indigenous groups to ensure all the requirements are met at a stakeholder level. We have been working extensively with NT Parks and Wildlife to make sure the management of the catchment is maintained, as well as with the wider community to help them to understand the dam’s reactivation.
 
“A recreation management plan for the reservoir will be developed and the new Strauss Water Treatment Plant will adopt state of the art technology to ensure the dam meets stringent drinking water quality standards.
 
“Given that recreation is a major feature of the Northern Territory's lifestyle, the treatment plant will enable us to maintain this space as a place for the Darwin region to enjoy, while also being able to use the water becomes fit for consumption.”