The scale of the inland NSW floods from last year is revealed in the monumental turnaround in fortunes for the shallow Menindee Lakes of the lower Darling River.
This nine-lake system made national headlines only a few years ago when they were allowed to go dry, leading to a mass fish kill.
South-east of Broken Hill and 200km from the Darling's junction with the Murray River at Wentworth, the operation of the lakes system has long been a hot topic.
Droughts between 2017-2019 saw the lakes emptied and emergency remedies sought to provide drinking water and irrigation to local residents and farmers.
An independent panel in 2019 concluded more than a million fish died in 2018 and 2019 along a 40km stretch of the Darling below Menindee because of hot weather and over-allocation of water resources in the Basin.
Last year the Menindee Lakes received more than five times its average yearly inflow.
Officially the lakes received around 10,000 gigalitres of water - six times its capacity of about 1731GL.
Even more remarkedly, the lakes experienced three major flood surges in that one year.
At one stage water authorities released 75,000ML/day through the Menindee Main Weir, enough water to fill Sydney Harbour in six days.
Authorities said about 8000GL was released over past year,
This overflow eventually made its way to the Murray River to add to the flooding emergency downstream in South Australia.
"Consecutive flooding events like these produce significant and compounding impacts, bringing new challenges to the river system, community and dam operators," WaterNSW said.
"Throughout these flooding events WaterNSW has been releasing large quantities of water from the lakes to manage storage levels and create space to capture future floods (otherwise known as airspace) to accommodate incoming flows.
"This careful management helped avoid adding to flooding downstream of the lakes throughout 2022."
Large amounts of water continues to drain into Menindee even today from inland NSW.
Menindee flood timeline:
February 2022 - Floodwaters enter Menindee and held within the lakes after authorities created "airspace" before its arrival.
June 2022 - Another flood arrives.
October-November 2022 - Larger flood flows, some originating in Queensland, enter the lakes system and releases rise.
Late November-mid December - With little time between floods, by December excess water could not be captured or released safely and the big releases were made. The main weir gates were fully raised in November and reinstated in mid-December as flood water started to arrive from upstream.
Mid to late December 2022 - Bigger flows than forecast arrived including from the floodplain via the Talyawalka Creek, which had branched out and re-joined the main channel of the Darling River upstream of the lakes. Excess water flooded some parts of the Menindee township.
January 2023 - WaterNSW is still continuing flood operations as huge volumes of water continue to enter the lakes. Flooding in Menindee reached a peak of 10.26 metres on January 6.
Today the lakes are officially 114.4 per cent full.
WaterNSW says it will reduce Menindee's volume to a more stable level "in order to maximise the amount of water resources left in the lakes by the end of the event".
"Once the incident is over" WaterNSW says it will conduct a post-event report to "identify learnings and recommend areas for improvement to future flood management".
"WaterNSW's operations remain focussed on protecting our storages, maximising the water resource and mitigating downstream flooding."
Meanwhile, the Murray-Darling Basin Authority has announced it is increasing the release of water from the giant Dartmouth Dam, the largest capacity dam in Victoria, to manage airspace.
Variable flow pulses of up to 7000 megalitres per day will be released into the Mitta Mitta River over the coming weeks.
During this time flows will remain below the river capacity of 10,000 ML/day.
MDBA executive director (river management) Andrew Reynolds said the purpose of increasing releases is to help target a lower storage level in Dartmouth Dam ahead of the potential for wet weather in winter and spring, without impacting on the volume of water available in the Murray in the months ahead.
Taking the opportunity to make releases that stay within the river channel is an important part of managing future risk.
Mr Reynolds said the MDBA is also continuing to monitor airspace at Hume Dam and the potential for future airspace releases in the coming months.
Chris McLennan
ACM national rural property writer based in Bacchus Marsh, Victoria. Career journalist. Multi award winner.
ACM national rural property writer based in Bacchus Marsh, Victoria. Career journalist. Multi award winner.
