Water levels in Wyangala Dam are being gradually reduced to provide a flood mitigation buffer, while work continues to repair significant flood damage to embankments downstream.
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Damage to Lake Brewster and the infrastructure around the lake occurred during the extensive 2022 Lachlan Valley flooding, Water NSW has said in a statement released to media.
Water NSW says it has made emergency repairs, restoring much of the operational function, but constraints remain on the flow capacity.
But focus has also turned to reducing the water level in Wyangala Dam to create flood buffer space as the wet, wintery conditions continue.
A meeting of local government, irrigation groups and key government agencies last Wednesday, June 19, gave support to a WaterNSW plan to gradually lower the Wyangala storage from the current 97.2 per cent of capacity, to provide the buffer.
The group - the Lachlan Valley airspace reference panel - will meet again on Wednesday, June 26, to review the situation.
Works to repair the Brewster Weir levee are being accelerated, which will contribute to overall flood mitigation measures, and include the establishment of a dedicated support team to co-ordinate planning, logistics, and communication functions.
Lake Brewster will not exceed 79.5 per cent of capacity during this next phase of repairs.
It is anticipated that the works to permanently return Lake Brewster to full capacity could take up to 12 months to complete.
WaterNSW will continue to review operational requirements throughout the repair project and communicate with stakeholders and local communities.
WaterNSW says Lake Brewster (66 per cent) and Lake Cargelligo (64.7 per cent) serve as important secondary storages for water users and the environment in the Lachlan Valley, many kilometres downstream of Wyangala Dam.
Restrictions on flow rates and storage levels at both Brewster and Cargelligo have been implemented frequently since the 2022 floods, to mitigate potential impacts on landholders in the vicinity.
Wyangala Dam holds approximately 1200 gigalitres at 100 per cent of capacity or full supply.
In November 2022 during the height of the flooding the dam received inflow of 800 gigalitres. In the three months from October to December 2022 the total inflow figure was approximately 1700 gigalitres.
The flood event caused significant damage was sustained to the weir pool levees, inlet channel, and lake embankments.
Further works are required and constraints remain on flow capacity of the Brewster Weir pool (5,000 ML/d), Lake Brewster inlet channel flow (960 ML/d) and Lake Brewster storage capacity (79.5 per cent).
For more information on WaterNSW visit: www.waternsw.com.au.
