WaterNSW is pressing on with its plans to replace the ageing Gin Gin Weir with a modern, sustainable structure.
The existing structure is a rigid concrete wall built in the early 1900s, which is severely damaged and does not meet contemporary environmental requirements associated with allowing fish to migrate and mimicking natural flow variability.
The need to replace the old weir with a modern version to meet long-term needs in the valley is critical, given the recent drought and predicted climate change risks that threaten the resilience of the environment, and other consumers in the valley who rely on the river.
The proposed replacement structure is a low impact, gated design, which would allow native fish to migrate – thereby freeing up 140km of river to native fish habitat – and let water for the environment pass through in line with strict environmental laws and the water sharing plan.
The proposed weir would also have the capacity to hold and manage small volumes of water released for customers out of Burrendong Dam, before releasing it on downstream to meet demand for both irrigation and environmental purposes, thereby reducing the volume of water lost to evaporation, especially over summer.
The existing weir is:
- More than 100 years old, flood damaged and structurally deteriorating
- A barrier to native fish movement and flow variability
- An out-dated, ungated concrete wall that is incapable of being operated to enhance river management
The proposed new weir:
- Features the most advanced design to minimise its environmental footprint, including allowing native fish to swim through the structure
- Is a gated design which can be used to temporarily capture smaller volumes of water that are released from Burrendong Dam and pass tributary flows and flood events through to the Macquarie Marshes
- Is designed to withstand extreme floods events, with large piers to elevate critical operating components above the highest floodwaters
WaterNSW Executive Manager Assets, Ronan Magaharan, said replacing the existing weir with a fit-for-purpose design will benefit all water users.
“Some of the information circulating about this proposed replacement weir overlooks the fact that there is already a significant barrier in the river at Gin Gin, dating back to the earliest part of the previous century, which needs replacing,” Mr Magaharan said.
“In contrast, the proposed replacement weir is a modern, gated structure, designed to benefit all customers, including the environment.
“The gates can be lifted so tributary flows and floods can pass through, or lowered to temporarily store water for delayed delivery and even maintain natural river flows several metres lower than the existing weir if needed.
“Additionally, the structure will have the ability to let fish migrate upstream and downstream in that stretch of river for the first time in over a century.
“The operational variability of the gates mean small volumes can be held and then released at Gin Gin to the far reaches of the river system without that water always having to travel the huge distance from the Burrendong Dam, as is currently our only option.
“The saving is that less water evaporates over the shorter journey from Gin Gin, rather than making its way down the river from the other side of Wellington.
“This upgraded infrastructure helps WaterNSW regulate the river for the long-term benefit of all users and must comply with the strict environmental regulations that oversee its operating conditions, and the legislated NSW Government water sharing plans which ensure equity and fairness among competing interests.”
September information sessions will be held on:
- Wednesday 2 September from 6-7pm
- Thursday 3 September from 12-1pm
To join one of these sessions, join the WaterNSW Facebook community here.
For information on the project, click here.