The re-regulating weir project

The NSW Government and WaterNSW are planning to build a gated re-regulating weir in the Wambuul Macquarie River at Gin Gin, between Narromine and Warren.

This structure will catch some water that is currently free to flow through Warren, and downstream to the Creeks, the Ramsar listed Macquarie Marshes, the Lower Macquarie and connect to the Barwon Darling River system, performing valuable ecological services along the way.

The purpose of the structure is to get more control over water in the river and make more water available for general security users. The effect is to convert unregulated flow to regulated flow.

This weir will capture ‘rainfall rejection orders’ (customer orders that are cancelled after they have been released from Burrendong, usually due to rain), and some tributary flows that enter the Macquarie below Burrendong. These flows will be ‘re-regulated’ as general security, and become available to use to meet customer orders.

While WaterNSW are telling the public that tributary flows won’t be captured by the weir, only unused dam releases. In their Scoping Report for the project, section 2.1.1 states that orders will be met including some water from ‘useful tributary contributory inflows.’ Sometimes tributary flows are used by WaterNSW to meet orders, and are considered dam releases.

One of the benefits of the re-regulating weir according to WaterNSW is maximising available water for general security customers. There’s only one place the water can coming from – that’s the water (Planned Environmental Water) that currently flows downstream, through Warren, into the Creeks, Marshes, the Lower Macquarie and into the Barwon Darling Rivers.

The Murray Darling Basin Plan stipulates there must be no reduction of Planned Environmental Water (PEW) in a river system. This project will reduce PEW, it must, there is no where else the water it will capture can come from.

The public’s trust in WaterNSW to keep their promises is at a rock bottom low – and rightfully so:

  • For almost a decade they have failed to deliver on a legal obligation to construct three fishways in the Macquarie, following a 2011 safety upgrade of Burrendong dam.
  • The pumping trigger for the Orange pipeline was slashed from 108 ML/day to a mere 38 ML/day – despite promises at the time the deal was made. It is alarming, that environmental assessment must be done before a project is approved, but after it is built, any changes to the rules don’t require environmental assessment.
  • Information presented to the public (DRC drought update) about the management of water and how it has been used since 2017 has been easily misinterpreted by the public, leaving the community believing incorrectly that most of the water released from Burrendong since 2017 was for the environment. An easily debunked untruth. Figures complied by Healthy Rivers Dubbo from WaterNSW reports show 45% of dam releases were for irrigation between 1/7/17 and 30/6/19, not 18% as presented.

What ever pledges the government makes to secure approvals for this project cannot be trusted. It is as good as a sure thing that if this project gets approved, the rules in place now will change, and more and more water will be captured and extracted.

The Macquarie Valley is already horribly over allocated. When Burrendong dam was built in 1967, the yield of the Macquarie River was assessed as 406 billion litres. But, water access licences totaling around 900 billion litres have been issued! That means users often receive only a percentage of the volume of their water access licence. This is called ‘reliability’ and it’s low in the Macquarie for that reason. There are simply too many straws in the glass.

This disastrous proposed weir has only one purpose – to make even more water available for extraction by increasing reliability.

Australia has a legal obligation to protect the internationally significant, Ramsar listed Macquarie Marshes. The Macquarie Marshes have already reduced by two thirds since the rapid increase in development of irrigated agriculture in the valley since the 90s, forcing the Commonwealth Government to issue a Change in Ecological Character Notice to Ramsar in 2010.

This proposed weir will be a death knell for the struggling Marshes.

The Aboriginal Heritage Information Management System indicates a registered site about 20km upstream from the proposed weir, which will be inundated by the project. WaterNSW have flippantly stated in their scoping report that there would likely be other similar sites along the river.

By creating a long still weir pool, the project will disrupt natural pulses in river heights for up to 30km, impacting all wildlife and vegetation that relies on the natural pulsing nature of the river.

This weir will be devastating for our remaining endangered native fish populations, turtles, fresh water mussels, shrimp – all the wild life that relies on the natural pulses of a free running river.

Dubbo was on track to run out of water this year, due to mismanagement, bad rule settings and extreme drought (which we are still in). The Macquarie River was cut off at Warren last summer, and native fish had to be rescued from the river. The internationally significant Ramsar listed Macquarie Marshes continue to reduce in size and resilience despite recent rain, and because of over extraction upstream.

Instead of building a re-regulating weir, the current crumbling 100 year old structure should be re built where it is, with a long overdue fishway installed.

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