Wyangala operations support ongoing Brewster flood repairs

24 JUNE 2024

The storage level of Wyangala Dam will be gradually reduced to provide a flood mitigation buffer while work continues to repair significant flood damage to embankments at Lake Brewster and Brewster Weir, downstream on the Lachlan River.

Damage to Lake Brewster and the infrastructure around the lake occurred during the extensive Lachlan Valley flood event in late 2022. Significant damage was sustained to the weir pool levees, inlet channel, and lake embankments.

Emergency repairs were made in 2023 and 2024 by WaterNSW, restoring much of the infrastructure’s operational function. 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%) and require further works to resolve.

A meeting of local government, irrigation groups and key government agencies last week (Wednesday 19 June) gave support to a WaterNSW plan to gradually lower the Wyangala storage from the current 97.2% of capacity, to provide the buffer. The group – the Lachlan Valley airspace reference panel - will meet again on Wednesday (26 June) 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% 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.

Lake Brewster (66%) and Lake Cargelligo (64.7%) 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% of capacity (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.

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