Background

The Walgett Weir, located approximately 6km downstream of the town of Walgett near the junction of the Barwon and Namoi rivers, is the main raw water source for the town.

The weir pool offered approximately three months of storage once the water stopped flowing over the weir, proving insufficient during several droughts. Additionally, the weir was also a significant blockage for fish passage.

The project involved raising the weir by 1m and the constructing in a vertical slot fishway.

Funding was provided by Infrastructure NSW through the Water Security for Regions and Safe and Secure Round 1.

Our role

NSW Public Works undertook the initial investigation, design and specification, construction procurement, construction management, technical advice and commissioning and overall project management.

Significant consultation was undertaken to progress the project. Walgett Shire Council, the proponent, benefitted from more secure water supply, while Water NSW, the asset owner, will operate and maintain the structure. Department of Primary Industries (DPI) Fisheries, who had an approval role, has an interest in having a fishway that functions well and were keen to have a cost-effective fishway. The local Aboriginal community, who use this section of the river as a meeting place, also had an interest in the site.

Construction management faced challenges due to flooding both before and after construction commenced, leading to wet ground conditions and design adaptations to address foundation issues.

Outcomes

Raising the weir has provided Walgett with a more secure raw water supply.

The fishway had been purposefully designed and constructed to be cost-effective, utilising sheet piling instead of traditional concrete to construct the vertical slot fishway.

The fishway will have a significant environmental benefit, allowing fish passage for both the Barwon and Namoi rivers.