WaterNSW will increase release rates from the Menindee Lakes system in western NSW this week to deliver water ordered by the Murray–Darling Basin Authority (MDBA), while operating the lakes to maximise future water security.
WaterNSW executive manager system operations, Adrian Langdon, said the Menindee Lakes system was managed to supply licensed customers including Essential Water and Lower Darling landholders, as well as ensuring water security for customers along the Murray.
Mr Langdon said WaterNSW would aim to maintain as much water in the upper two lakes as possible as drought contingency in line with established practice.
“WaterNSW will continue sourcing the majority of the release volume from Lake Menindee, as well as a smaller amount from Lake Wetherell,” he said.
“Lake Wetherell is currently at 125 per cent capacity so the intention is to lower the level to remove water from the flood plain to protect the health of the ecosystem.
“WaterNSW’s recent operations have ensured that the upper lakes are full from last season’s inflows and Pamamaroo will be used as storage to meet future needs recognising that its level will fall due to evaporation.”
In accordance with the longstanding Murray–Lower Darling Water Sharing Plan, the MDBA has directed the release to provide for demand along the Lower Darling and for the Murray downstream of the Darling River confluence.
MDBA head of river operations, David Dreverman, said high evaporation losses from the Menindee lakes meant the storages were used ahead of others, such as Dartmouth Dam.
“It makes sense to use water from shallow storages first, Menindee releases over summer and autumn will enable hundreds of gigalitres of water to be reserved in Dartmouth Dam for use by the whole Murray valley in future years,” Mr Dreverman said.
“Menindee lakes are shallow, and average around five metres deep and can evaporate at a rate of about two metres a year.
“Safeguards are built into the water sharing arrangements so that the use of Menindee Lakes is limited to protect local NSW town water supply and lower Darling use once lake volumes fall below 480GL.”
With operational releases about to commence, the delivery of environmental water for the Lower Darling fish flow event will be postponed until further notice.
In the interim, WaterNSW is working closely with environmental water authorities to ensure pending operational releases will also benefit native fish in the lower Darling.