AROWS concept design released as Darwin's next water source takes shape

The Adelaide River Off-stream Water Storage (AROWS) is the Northern Territory Government's proposed long-term water source for the Darwin region. Current modelling shows it would hold around 250 gigalitres when full and supply 60.2 gigalitres a year — almost double the 32 gigalitres a year Darwin River Dam supplies today.

The project is led by the NT Department of Logistics and Infrastructure (DLI) in partnership with Power and Water Corporation, and is in its planning and approvals phase. An early concept design was released in July 2026, and field studies for the project's environmental impact statement (EIS) are under way. The NT Government describes AROWS as the largest infrastructure project undertaken in the Territory since the Alice Springs to Darwin railway.

Project at a glance

How an off-stream storage works

Most dams are built across a river. AROWS takes a different approach. It would use a naturally occurring basin formed by a ridge about one kilometre from the Adelaide River, with two main dams built at low points in the ridge to hold the water in. No dam would be built across the river itself.

Water would be pumped from the Adelaide River only during the wettest months, December to April, when flows are highest. It would then be stored in the basin and piped along the Stuart Highway to the Strauss Water Treatment Plant, which would be expanded to treat the extra supply.

The NT Government's 2025 project update breaks the build into five parts:

• Intake: a river intake, pump station and transfer pipeline to fill the basin
• Basin: the dams and a spillway
• Outlet and delivery: an outlet, pump station and delivery pipeline
• Connecting infrastructure: pumps, a pipeline and a balance tank linking to the Strauss plant
• Supporting infrastructure: access tracks, laydown areas, site facilities, an electricity substation and telecommunications

Why Darwin needs it

About 85% of the Darwin region's water comes from Darwin River Dam, which is operating at capacity; the rest is groundwater. Demand of around 42 gigalitres a year in 2021 is expected to more than double by 2050, to about 100 gigalitres a year.

The Darwin Region Water Supply Infrastructure Program is the government's answer, adding 67.3 gigalitres a year in total: 7.3 GL from returning Manton Dam to service and 60 GL from AROWS. A detailed business case, released in 2022, compared this option with a smaller desalination-and-recycling alternative and found the Manton Dam and AROWS option was the better solution, with benefits outweighing costs. It costed that combined option at $1.45 billion.

Infrastructure Australia evaluated the business case in February 2022 and lists the project on its Infrastructure Priority List. Its recommended next step is a final business case covering design development, detailed cost and risk work, environmental assessment and geotechnical surveys.

Where the project stands

Environmental assessment. The NT Environment Protection Authority (NT EPA) accepted the project's referral in December 2024 and took public comment in January and February 2025. In April 2025 it decided AROWS would be assessed through an environmental impact statement — the most detailed level of assessment — and it approved the EIS terms of reference on 13 May 2025. Federally, AROWS is a controlled action under the EPBC Act, meaning it needs Commonwealth approval, with listed threatened species and migratory species as the matters to be assessed. The NT EPA's register records that it paused the assessment in April 2025 to confirm the Commonwealth–Territory bilateral agreement would apply, then resumed it.

Field studies. Teams have been on site surveying threatened plants and animals, modelling river flows and studying water quality and aquatic ecosystems. A network of 17 monitoring bores across nine sites, installed in July 2025, is collecting baseline groundwater data. At the July 2026 Community Reference Group meeting, the Department of Lands, Planning and Environment reported on completed Adelaide River water modelling, which found the effect of extraction for AROWS would be small to negligible compared with the river's natural flow variability, with no measurable change to the floodplains. A water allocation plan for the Adelaide River catchment, under which AROWS would be regulated, is being prepared.

Design and the project team. SMEC was awarded the AROWS concept design contract in December 2023, and GHD was appointed lead environmental consultant in 2023. For Power and Water, Jacobs was engaged in January 2025 for the concept design and cost estimate of Strauss Water Treatment Plant stage 2 and storage. DLI's September 2026 update names SMEC, Ecoz, GHD and Power and Water among the contractors and partners who took part in a cultural induction on country with the Limilngan-Wulna Custodian group, whose cultural monitors remain involved as site work continues.

Funding. Stage 1 of the program — which pays for AROWS planning, approvals and pre-construction activities alongside the Manton Dam works — is jointly funded by the Australian and NT governments. Stage 2, which covers AROWS construction and the second stage of the Strauss plant, is subject to regulatory approvals and future investment decisions. No updated capital cost for AROWS on its own has been published; the pre-construction phase is designed to better define the cost, delivery model and schedule.

Stage 1 is already delivering

The first half of the program is built. Construction of the Manton Dam Return to Service project was completed in August 2026, on time and $15 million under budget, by local company Exact Contracting, with Power and Water managing the project. The works upgraded the dam's intake tower and added a new pump station, 22 kilometres of pipeline and the new Strauss Water Treatment Plant.

Once commissioning is finished, Manton Dam will add 7,300 megalitres a year to Darwin's supply, with water expected to enter the network later in 2026. Power and Water says more than 100 employees and 500 contractors worked on the project over two years.

What happens next

The NT Government's indicative timeline, subject to approvals and funding, runs:

• 2019–2026: planning and approvals
• 2025–2028: pre-construction — targeted geotechnical surveys, detailed design, procurement and construction planning to inform a final investment decision
• From 2028: construction and commissioning
• 2032 onwards: operations, as indicated in the government's water-extraction timeline

Milestones to watch:

1. The draft EIS, which will be published for public comment through the NT EPA.
2. The reference design and an updated cost estimate, building on the concept design.
3. The delivery model and procurement approach, which the pre-construction phase is set up to define.
4. A final investment decision and Stage 2 funding from the Territory and Commonwealth.
5. The next Community Reference Group meeting, scheduled for November 2026.

For the Territory's construction sector, the published scope points to a broad package of civil work: dams and a spillway, pump stations, pipelines and a water treatment plant expansion. Manton Dam has shown that local contractors can deliver water infrastructure on time and under budget, and AROWS is the next, much larger step in securing Darwin's water for decades to come.

Published 12 October 2026 · Updated 4 October 2026