Burrendong Dam was almost empty in early 2020, but now dam managers have spent nine months working furiously to stop the dam and rivers from flooding — a job that is far from over.
At the peak of the drought, the dam was less than 2 per cent full.
It is a drastically different situation today, having remained at over 100 per cent capacity since September despite constant water releases being made into Wambuul/Macquarie River to try to create space.
La Niña is forecast to continue, bringing a wet winter after "the wettest year in decades", so Water NSW is on high alert for potential flooding caused by yet more rain falling on already full dams, high rivers, and saturated catchments.
"There have been repeated releases but that water has been replaced almost immediately by the next rain event," Water NSW spokesperson Tony Webber said.
"That's a pattern we've been in for many months now.
"In the case of Burrendong in particular, which is still up around 115 per cent capacity, some large releases are taking place to pull that storage down. The target figure is 105 per cent at this stage."
A balancing act
It has been a delicate balancing act to capture and release thousands of gigalitres of water without causing flooding for communities along the river.
"Some of these dams have released far more in volume than they actually hold and it's been a pattern of making releases in readiness for the next rain event," Mr Webber said.
"We've just seen those rain events occurring on an almost weekly basis."
Water NSW was confident it could release water without causing flooding for communities down the Macquarie River.
"You need to find those opportunities when there's space in the river to make releases without having an adverse impact downstream," Mr Webber said.
"Obviously, if you're going to have tributary flows that are also generated by those rain events, you don't want to add to that flow with large releases from the dam. So it really is a balancing act.
"The flooding that has occurred has been greatly reduced due to large inflows from the dam's catchment being, if not captured, at least held back to allow those tributaries downstream to recede.
"Numerous flood events have been diffused altogether because that water has been captured in the dam and converted into water security for the future."
Preventing Barwon-Darling floods
Burrendong Dam is just one of the major water situations being managed during the extraordinarily wet conditions.
Further west, the entire stretch of the Barwon-Darling River to Menindee Lakes is expected to receive an enormous volume of water from Queensland — the equivalent to two and a half Sydney Harbours.
"There's another huge flow making its way down the river now, we anticipate anything up to 1200 gigalitres will be received into the lakes by the end of July," Mr Webber said.
"That's got to make its way past those towns on the Barwon Darling — Brewarrina, Bourke, Louth, Tilpa, Wilcannia — and then be passed through Menindee Lakes into the Lower Darling.
"That'll be the second major in-flow event we've had in the last six months."
The summer flood event was avoided through water management.
"We're making releases out of the Menindee Lakes as we speak, in anticipation of that water arriving fairly shortly," Mr Webber said.
"But, certainly the prospect of being able to capture that water in the lakes diminishes with the fact that the storage is very high and the volume calculations keep increasing."
Authorities are in constant consultation with the Bureau of Meteorology and a panel of local stakeholders in the Macquarie Valley to help inform their decisions around water releases, contributing information about river activity including the tributaries, agricultural concerns and environmental factors.
"That's been important … to make sure that we fully understand what's happening downstream. We have a bird's eye view of what their operations are and we can tailor releases, within reason, accordingly," Mr Webber said.
'Exceptional water security'
Despite the difficulty with water management and agricultural concerns by the ongoing water conditions, there are many benefits from the situation.
"This is an extraordinary turnaround on the years of drought," said Mr Webber.
"This is probably the best water security situation we've had since the 1990s.
"Across regional New South Wales and Western New South Wales while there's been some hardship and some inconvenience the return to exceptional water security is a much-needed relief.
"After the intense hardship of the drought years, to have all our major supply dams at or about capacity to see the rivers running again, communities assured of town water supply — it's a wonderful turnaround."
