Murchison Dam Upgrade

Client: Hydro Tasmania
Location: Tasmania
Date: Ongoing

Providing specialist hydropower and dam safety expertise over two decades, leading to a safe dam upgrade

Background

In the remote west of Tasmania, Murchison Dam has stood for more than four decades as a critical part of Hydro Tasmania’s Pieman hydropower scheme. Constructed between 1978 and 1982, the dam rises 93 metres above the Murchison Gorge, storing water that is channelled through the Sophia Tunnel to Lake Mackintosh. This infrastructure plays a vital role in Tasmania’s energy security, contributing to about a quarter of the state’s renewable generation.

As climate change drives more extreme rainfall events, Hydro Tasmania needed to ensure Murchison Dam could safely manage larger floods, protecting downstream communities and securing power generation assets for decades to come. In 2019, Hydro Tasmania launched a two-stage, $33 million dam safety upgrade program – a major investment in the future of Tasmania’s hydropower network.

Solution

Entura has supported Murchison Dam for over 20 years. Over this time, we provided specialist support including early spillway enhancement option studies and risk assessments, dam break modelling and flood mapping updates, ecological assessments and detailed hydraulic model studies that informed the upgrade design. For this project, our hydropower, dam safety, hydrology, hydraulic and geotechnical specialists collaborated extensively – from planning through to independent design review and risk assessments.

Stage 1, completed in 2020, involved raising the dam’s crest wall by 3 m using a combination of in-situ and precast concrete construction.

Stage 2, completed in 2025, focused on raising the right spillway chute wall by up to 5 m through construction of 14 concrete monoliths. Entura’s dam safety team developed and calibrated hydrologic and hydraulic models, undertook dam break and consequence assessments, and prepared inundation maps to inform emergency planning. We also supported the project with an independent review of the detailed design and construction process.

Delivering these works was not without challenges. The site’s remote location, steep topography, annual spill events and high rainfall required careful planning and risk management. Lake level forecasting, robust dam safety emergency plans, and scheduling work for lower flood-risk months allowed construction to proceed safely despite several live spillway events.   Hydro Tasmania, AECOM, Hazell Bros and Entura worked to find practical solutions to logistical and safety challenges.

Outcome

The completion of Stage 2 in early 2025 marks a major milestone in Hydro Tasmania’s program to modernise and futureproof its West Coast hydropower assets. The upgraded Murchison Dam significantly increases flood capacity, ensuring the dam can safely pass increased inflows while maintaining its essential role in renewable generation.

Stage 2 involved 36 months of works, more than 1,600 m³ of concrete, 375 t of steel reinforcement, and the efforts of over 100 people across the project lifecycle. Beyond the engineering achievement, the upgrade demonstrates Hydro Tasmania’s long-term commitment to the safety of Tasmanian communities and to building resilience against a changing climate.

For Entura, the project highlights our depth of expertise across the full lifecycle of dam safety management – from initial risk assessments and physical modelling through to construction support and emergency planning – and our continuing role in helping Hydro Tasmania secure the future of Tasmania’s hydropower network.