Darling at Bourke to reach 10.9 metres


The Darling in flood at Bourke, April 2021. A similar flood is expected after Christmas. PHOTO TWH

The Darling River at Bourke is now expected to peak of 10.9 metres, with minor flooding, around just after Christmas, following further rain in the catchment last week.

The expected peak flow at Bourke is 42,000 megalitres per day on Boxing Day.

A flood of this height and volume will not threaten the Bourke levee, but some roads, around Bourke will be affected by floodwater.

Following further big rainfall throughout the catchment last week, the estimated height and volume of the flood have been adjusted upwards.

The flooding has brought good news and bad news for communities from the Queensland border right through to Menindee Lakes, with heavy rain putting more water into the Border Rivers, the Namoi, Gwydir and Macquarie Rivers and other tributaries of the Barwon-Darling.

The good news is that river is flowing from top to bottom, and all major dams are full and overflowing.

The bad news is that a large volume of water is spilling onto the floodplains, causing continuing damage to crops, and some communities.

WaterNSW’s Executive Manager System Operations, Adrian Langdon, said in the Barwon-Darling however, major flooding is unlikely, but that flow will continue over much of the summer.

Mr Langdon expects flooding downstream to be like the flood in April this year, and the 2011 flood. Most of the floodwater is coming from the Macintyre and Namoi Rivers with contributions from the Macquarie and Culgoa systems.

“Last week’s heavy rainfall across the Queensland border caused major flooding around Goondiwindi,” Mr Langdon said.

“There is a very large volume of water heading down the Macintyre River which will reach the Barwon-Darling in the middle of this month.

“There is also a lot of water in the Weir River which will reach Mungindi this week. The Bureau of Meteorology is predicting a peak flow at Mungindi this Thursday at around 7.7 metres.

“The river around Boggabilla is running at about 200 thousand megalitres a day, and on Saturday we saw it spilling out onto floodplain.

“That water will eventually make its way back into the river which will continue to flow for a prolonged time.

“We expect the Barwon to peak at Walgett early next week at 11.8 metres, which is around 70 thousand megalitres a day.

“With water coming from many rivers there will be a long drawn out peak, and even without rainfall, the rivers will stay high right through January.

“That’s good news for the rivers, but for a lot of farmers it’s not great as the floods are having a big impact on farmers trying to harvest a big crop.

“At the same time, it’s lovely to see a fully connected river system.

“We expect to see the Barwon-Darling floodplains get a good watering around Walgett and downstream two years in a row.

“Towards the bottom of the system, the Darling River at Wilcannia will have a flow peak of around 27,000 megalitres per day around the 10 January.

“After an extended drought it’s great to have this return of flows,” Mr Langdon said.

Since February 2021, over 2,000GL has reached the Menindee Lakes, which is full at about 1,700 GL.

WaterNSW is now expecting a further 1,000-1,800GL inflow to Menindee Lakes by the end of February.

According to Mr Langdon, more rain is forecast this weekend which may add to the flows.

“The season is also very early and continued rain is forecast over summer and through to April, which will mean these flow forecasts will be continually updated,” he said.