Lake Macdonald – also known as Six Mile Creek Dam – was originally constructed in 1965.  

There have been significant advances in dam design since the dam was built, as well as new ways of estimating extreme rainfall and flood events, and a greater understanding of the size and severity of earthquakes. 

This will be the first major upgrade of the dam since the wall was raised in 1980. The Lake Macdonald Dam Improvement Project will: 

• increase the spillway capacity to safely pass floods  
• protect the dam wall in extreme flood events 
• efficiently control water flowing out of the dam  
• reduce risks to the dam structure during earthquakes 
• meet modern design and engineering standards 
• comply with dam safety guidelines. 

All Seqwater dams within the Dam Improvement Program continue to operate safely. Dam improvements are undertaken to meet modern guidelines for these life-long assets – many of which were built some years ago.  

Seqwater undertakes regular monitoring and engineering assessments to ensure all our dams continue to operate safely.  

Dams in Queensland were built to high, internationally accepted safety standards. However, the methodologies and data used to estimate extreme weather events and flooding impacts have significantly improved, and engineering standards and risks have progressed.  

All these factors are considered as part of Seqwater’s Dam Improvement Program so our dams continue to operate as they should, now and into the future. 

Main construction works commenced in May 2025. Most work will be completed during approved standard working hours to reduce impacts to the community.

Day work

• Monday to Friday – 6.30am to 6.30pm
• Saturday – 6.30am to 4.00pm

Some work activities are time critical and must be carried out continuously or outside of the approved standard hours for safety and construction reasons. More information is available on our work hours fact sheet.

Construction activities to expect in 2025 include the mobilisation of stockpiled rock and other materials and equipment, piling equipment mobilised onsite for cofferdam construction, and lake lowering and cofferdam construction. 

​The entire construction process, from building the cofferdam to its removal after the new dam wall is complete, is anticipated to take around five years, depending on weather and site conditions.

Key activities will include:

• Vibratory and Impact piling
• Concrete and rock breaking
• Earthworks
• Concrete pours
• Rock filling.

​Please note that the construction schedule is subject to change based on environmental and operational factors.

The entire construction process, from building the cofferdam to its removal after the new dam wall is complete, is anticipated to take around five years, subject to weather and construction conditions.  

Construction phases and timeframes are: 

• Phase 1 (2025) – Construction of temporary cofferdam 
• Phase 2 (2025-2026) – Demolition of existing dam wall 
• Phase 3 (2026-2028) – Construction of new dam wall and infrastructure 
• Phase 4 (2028-2029) – Remove cofferdam and site rehabilitation.  

Lake Macdonald Dam will naturally refill to its original full supply level once construction is complete.  

John Holland have procured four quarries to supply materials on-site and these quarries will be used as required, based on their material availability, material suitability and site requirements.  

Quarries approved for use are:   

• Boral (Moy Pocket)   
• Cordwell's (Kin Kin)   
• Corbett's (Traveston)  
• Holcim (Bli Bli).   

Control measures for quarry trucks on the Lake Macdonald Dam Improvement Project include:   

• Trucks to be fitted with GPS tracking to monitor truck speeds and haulage route.  
• Signage and UHF for school buses to communicate and coordinate movements on the road.  
• Sign in and sign out system, including QR code registration, to track and monitor trucks.   
• Boom gate system to stagger truck movements travelling between the quarry and project site.  
• Heavy vehicle movements will be minimised during school pick-up/drop-off times (7:20-8:45am and 2.30-3:45pm).  

The community can expect an increase in standard construction impacts intermittently throughout the project including noise, dust, vibration and increased heavy vehicle movements. 

At times, out of hours work including weekend, night and continuous work will be required to complete time critical activities. 

We will provide advance notice to the community and stakeholders ahead of any out-of-hours works. Additionally, we will actively engage and inform the community prior to the commencement of key construction activities.

We understand some activities will be more disruptive for residents in close proximity to the project, and will remain available 24/7 to those directly affected. 

Click to read our fact sheets for more information on traffic management, work hours, and noise, dust and vibration mitigation measures. 

We thank the community for the patience and understanding they are showing while these essential works are carried out.

We are working closely with qualified ecologists to ensure the well-being of local flora and fauna, implementing targeted measures to protect and manage wildlife throughout the construction period.

To date, Seqwater and John Holland have carried out extensive environmental investigations to identify and document plant and animal habitats in and around Lake Macdonald.

These investigations have included detailed field surveys focused on protected plant species, key habitats for native wildlife, aquatic ecosystems, and significant local species. The process also involved reviewing historical and current reports and databases to ensure a comprehensive understanding of the area’s ecological values. 

Click here for more information on our ecological management and mitigation measures.

During the lake drawdown, there will be a temporary reduction in available habitat for aquatic species. To help minimise ecological impacts, the project team initiated an aquatic fauna relocation program targeting identified native fish species.

In July 2025, approximately 680 fish were successfully salvaged and relocated by specialist fish biologists. The relocation was carried out using a purpose-built transport vehicle, with the fish transferred to Cooloolabin Dam to preserve aquatic biodiversity and support ecosystem resilience.

The species relocated included Australian bass, eel-tailed catfish, and longfin eels. Additionally, one Mary River Cod was captured, genetically sampled, measured, and released into the Mary River to support conservation efforts for this iconic species.   

There is no existing fish passage (a fish ladder is a specific type of fish passage) at Lake Macdonald Dam, and no proposed fish passage included in the Lake Macdonald Dam Improvement Project. The reasons for this are:    

• A fish passage could allow for pest species such as Tilapia to enter Lake Macdonald reservoir.   
• A more suitable location for a fish passage has been identified at the Gympie Weir. A fish passage in this location will allow fish to pass up and down the main Mary River, allowing passage between the upper tributaries and reaches. 
• The Coordinator-General, as part of the Project Approval Conditions, has stated that Seqwater upgrade the Gympie Weir to include a fish passage. 

Lake Macdonald is expected to remain open to on-water recreation, and parks and facilities recreation throughout the project.

Lake Macdonald, Lake Macdonald Park / Perch Park and the boat ramp along Lake Macdonald Drive will remain open, as well as the Noosa Botanic Gardens. Recreation activities including motorless boating, canoeing and fishing will be permitted outside of the construction zone, which the cofferdam will isolate. 

The scouts campground, the Mary River Cod Park and boat ramp, the fishing platform on Lake Macdonald Drive and some walking, riding and horse trails are temporarily closed for the duration of construction. 

The Noosa Trail Network will remain open, however access points to the trails may change during construction. Vehicle parking and foot access will be closed at the Lake Macdonald Drive trail head (near Kookaburra Park) and along Collwood Road due to construction activities.

To view the latest recreation notices for Lake Macdonald please visit the Seqwater recreation alerts page.