G-MW has found evidence of moving and cracking in the walls of Waranga Basin. Photo: G-MW
Goulburn-Murray Water's Dam Safety Team has completed a major field investigation at Waranga Basin, after the 100-year-old storage's embankment experienced unusual movement and cracking back in 2024.
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G-MW Dam Safety Manager Sam Green said there was no safety concern, with the works focused on installing monitoring equipment and gathering data to help the team understand the dam's condition and explain the movement and cracking.
"There has been no change in risk or safety of the dam," Mr Green said.
"It's performing well, much the same as it has for the 100 years since it was built."
Construction of Waranga Basin was completed in 1915. Photo: Tatura Museum
Waranga Basin, near Rushworth, is a crucial off-river storage supplying water to the Central Goulburn, Rochester and Pyramid-Boort irrigation areas, and beyond to the Loddon Valley Irrigation Area.
Its embankment stands 12 metres high and stretches seven kilometres.
The movement and cracking was identified during G-MW's latest Dam Safety Review of the storage, which national guidelines recommend be conducted every 20 years.
Mr Green said the movement was not unexpected, with dams frequently shifting alongside fluctuating water levels.
"Waranga Basin has been moving downstream at a slow, continual rate," he said.
"It is not a cause for concern, and is not unexpected."
The movement is at a scale of only millimetres.
The cracks run parallel along the dam wall and vary in size and depth, with some several metres long and about 5mm wide.
The team does not consider them a safety threat, but wants to understand how they formed and whether they are connected to the movement.
"We look at these things while they are small, so that they stay small," Mr Green said.
In June, the team examined several sections of the embankment in depth, installing new monitoring instrumentation including inclinometers, which measure movement within the embankment, and vibrating wire piezometers, which monitor water pressure within the dam structure.
The Waranga Basin embankment is 12 metres high, and over seven kilometres long.
A sonic drill rig was also used to core down into the embankment without disturbing the structure, allowing the team to collect core samples and assess the material within the wall.
A cone penetration test was carried out to evaluate soil characteristics within the embankment.
"It's provided us a lot of useful information about the embankment's behaviour," Mr Green said.
"We have gained valuable insights of the internal condition of this 100-year-old embankment, helping improve our understanding of potential deformation mechanisms and supporting dam safety risk assessments."
Mr Green said the investigation highlighted the important work his team does, usually out of the spotlight.
"This is business as usual for us," he said.
"Dam safety is built on understanding, monitoring and continuously improving our knowledge of the behaviour of these critical assets."
G-MW general manager strategy and services planning Steven Abbott said the investigations were a great example of the water corporation's commitment to dam safety.
"This work highlights the careful and thorough approach we take to dam safety," he said.
"It's a great example of how our Dam Safety Team supports the safe and responsible management of our storages."
