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Fears flood waters could breach Menindee Lakes

By Paula Doran

Larger releases should have been made to allow for the floodwaters bound for the Menindee Lake system, according to landholders south of Menindee, amid fears the large catchment could breach its banks.

With 2000 gigalitres of water – a gigalitre is one billion litres – expected to flow into the system over the coming weeks, there have been warnings across the catchment that the Menindee Lakes are at risk of being breached unless there are dramatically higher releases of water to allow for airspace and cater for the floods.

Darling River grazier Wayne Smith said the Menindee Lakes would not cope with incoming flood waters, warning not enough had been done to prepare for the deluge flowing down the system.

Mr Smith said government body WaterNSW had bungled the management of the current flood event.

“There will have to be dramatic increases in releases to avoid the lake structure being put in breach,” Mr Smith said.

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“As an example, in 2012 the water authority was releasing 35 gigalitres per day to create a 500 GL air space buffer before that particular flow event arrived. Currently they have been releasing 25 GL per day to allow for a 140 GL buffer.”

LACK OF INFORMATION

Mr Smith said the lack of information coming from WaterNSW had made it difficult for landholders on the Darling to plan ahead.

“We normally get regular updates with predictions of inflows, but this time there has been no information passed on,” he says.

“It’s flabbergasting really, and you wonder whether they are passing the buck.

“Not being able to get regular updates on the estimated inflows makes it really difficult, and frustrating, when you are trying to assess whether or not to evacuate.”

In a community report released by WaterNSW on Monday the authority conceded the current airspace of 187 GL would be insufficient to accommodate the revised forecast inflows.

“Given the uncertain forecast, the continuation of the La Nina weather pattern and a wetter than average outlook by the BoM (Bureau of Meteorology), the release plan is being continually reassessed by our experts,” WaterNSW said.

“The revised plan will now see gradual increases to the height of at least 9.4 metres at the town gauge (Menindee) from its current 9.2 m. With this revised plan, flows at Weir 32 will gradually increase to over 30GL/per day and residents should prepare for further increases throughout the event.”

MP CRITICISES APPROACH

Barwon MP Roy Butler criticised the approach by WaterNSW, who he said ignored the community advice and historical knowledge of the waterways.

“During the second quarter of this year, we advocated to WaterNSW to increase the releases from Menindee by 500mgl a day in order to establish the safest maximum release rate. This approach had community support. This approach was not adopted,” Mr Butler said.

“WaterNSW relies on advice from SES with regards to risk to people and property. The advice from the SES did not account for decades of local knowledge about the management of the lakes and from people who had experience of floods in the past, especially in low-lying areas.

“As a result, I requested that WaterNSW engage an independent hydrologist to review the strategy and make suggestions on what adjustments could be made, how releases could be augmented to maximise releases from the lake. This was agreed in principle by the former head of WaterNSW, who subsequently left the role. The net result of all of this is – if the event had been managed differently – we could have had more air space to mitigate incoming flows,” Mr Butler said.

The MP has pushed for more accessible and easy-to-understand information on river heights.

“This is something that they have failed to provide for recent events. With places like Wilcannia and Menindee where internet access or devices are not available, there needs to be a simpler mechanism for people to access the information.

“I have huge appreciation for the work of the SES, especially their volunteers, I would prefer that people be given notice to evacuate well before the waters arrive than see people having to protect their property as the waters are arriving,” Mr Butler said.

Meanwhile ecologists are monitoring both the Darling and the Murray Rivers to assess for potential fish kills amid potentially low oxygen levels.
Ecologists say it is not uncommon in a flood event that oxygen levels drop and fish die off in the black water wash.

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