Central Plains Water Limited labyrinth weir

 THE BRIEF 

This innovative project showcases our commitment to undertaking projects in collaboration with our client to increase the resilience of existing irrigation

infrastructure to meet the demands of climate change and support the long-term sustainability of agriculture in Canterbury, New Zealand.

This weir replacement project presented some unique challenges. We needed to construct the new weir within the same overall width as the original weir and achieve more than double the flow capacity. We also needed to complete the project within a very tight project timeframe to ensure the weir structure was ready for the 2025 irrigation season.

 THE OUTCOME 

Our team of Riley engineers employed a highly collaborative approach to the design. Following site investigations, initial geometric design and hydraulic modelling, a trapezoidal “labyrinth” shaped weir was selected to achieve the required flows for the available width. We produced a 3D rendering of the new weir structure in conjunction with an independent structural engineer.

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We commenced the detailed design process and issued interim design drawings for review and feedback by the wider project team (CPWL, the client project manager and the nominated contractors) which allowed for detailed design drawings to be completed well ahead of schedule to allow pre-casting of the concrete elements.

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The new CPWL weir was completed on time and within budget, exceeding client expectations. The weir replacement project has increased the resilience of the CPWL supply canal by reducing the operational impact caused by flood events in the Rakaia River.