Burrendong empties at blistering speed.
The dam is massive – 1,188 billion litres. For context, Dubbo draws 8 billion litres a year to meet 70% of town water needs.
Burrendong has nearly bottomed out three times. In the summer of 2019/20 plans were in place to suck the dead water from the very bottom of the dam before letting the river below Burrendong dry up.
The river below Warren was allowed to dry up, followed by massive deaths of native fish, turtle, mussels, and other wildlife. People below Warren were left with no access to water from the river for their domestic and stock needs. It was a tough time.
Burrendong empties so quickly because the rules in the water sharing plan allow it to.
Water that has not yet fallen as rain over the Macquarie catchment is sold in advance.
The credit rule is essentially allocating clouds – water that hasn’t even fallen in the catchment yet,” said Celine Steinfeld, lead author of the paper published in the Journal of Hydrology, and also a member of the Wentworth Group of Concerned Scientists. “It was clear that water in the Macquarie had been overallocated.” (SMH Clouds become water entitlements in ad hoc river plan, paper finds)
The NSW Government knows the Macquarie is over allocated. On page 89 of their 2014 State Infrustructure Strategy they explain that while Burrendong is one of the biggest dams in state, the irrigation industry has developed to a size where the natural capacity of the river has been exceeded. There is simply too much water being sucked out.
When working out how much water to sell every year, the NSW Government does not take into account any rainfall and inflow data from before 2004. They choose to only look at last centuries rainfall patterns when is was a lot wetter.
The super weir to make everything even worse
The NSW Government are planning to add to our problems by building a re-regulating weir at Gin Gin that will allow even more water to be extracted.
The purpose of the enormous gated weir 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 be a loss to the environment of about 25 billion litres a year, according to Tony Quigley, Chair of Macquarie Food and Fibre.
The most effective, common sense way to address water security issues in the Macquarie Valley is to look at the glaring problems with the rules in the water sharing plan, not to pour many tens of millions of public dollars into a monstrous structure that will only benefit a privileged few.