By Paula Doran
WaterNSW does not expect any damage to property in Menindee due to water flowing into the Menindee Lakes from the swollen Darling River system. The government body is gradually releasing water from the Lakes to allow space for continuing floodwaters.
In a statement released this week, WaterNSW said gradual increases in water released from Menindee Lakes was building capacity within the storage to receive large quantities of Barwon-Darling floodwater, with inflows expected to peak by the end of December.
On current modelling they expecting at least a further 1700-2000 GL to arrive between now and the end of December, increasing the risk of flooding in the Menindee area and downstream.
WaterNSW maintained releases within the minor flood level from May to early October, successfully passing multiple large flow surges without impacting property, and has now generated 250 gigalitres (GL) of capacity within the lakes to receive increasing inflows.
The intention is to create and maintain this storage capacity, to capture the higher peak later in December to help minimise downstream flooding impacts.
“Planning will focus on reducing the water being released from the lakes to coincide with high flows from the Talyawalka into the Lower Darling,” a WaterNSW spokesperson said.
On current projections the peak flow rate expected at Wilcannia in coming weeks (~43 GL/day) would be among the highest in decades. The lakes have received almost 7000 GL of inflow this year, representing the equivalent of four times the storage capacity of the lakes.
The lakes – which hold 1731 gigalitres at 100% full – are currently at 103% of storage capacity, having been surcharged above 100% since February due to high inflows resulting from the La Nina weather pattern.
WaterNSW has previously told Menindee community that releases would increase gradually from the main weir to eventually target 9.6 metres at Menindee and a flow rate of about 32 GL/day at Weir 32.
The spokesperson said when planning releases there were several priorities.
“Broadly speaking the priorities of managing any storage, including the lakes, are to maintain the safety of the storage infrastructure itself, to maximise the availability of water for users, and to operate the storage to provide flood mitigation where possible.
“During the La Nina weather pattern characterised by exceptionally wet weather across the northern basin and very large inflows into Menindee lakes (~7000 gigalitres (GL) this year into a lake system that holds ~1700 GL at 100%) the primary focus has been on carefully and expertly managing water releases when we know large inflows are coming, so that the storage does not exceed capacity, without those water releases impacting on property in the local Menindee community and those downstream on the Lower Darling.
“We’ve successfully managed at least four major inflow events in 2022 – totalling at least four times the lakes’ entire volume – without excessively impacting on the local Menindee community and those downstream on the Lower Darling. This is entirely consistent with the information at hand at the time and the operating plan developed as a result.”
