Project: Ōhau Canal
Surveying the Ōhau Canal for Meridian Energy
The Challenge
The Waitaki Hydroelectric Scheme is New Zealand’s largest hydroelectric power system supplying around 16% of the nation’s annual electricity supply. To keep it running, manmade canals lined with impervious materials and protected by rock armour must stay in top condition.
The project had added complexities: the canal had to stay full to support power generation, access was restricted by bridges and salmon rafts, winter conditions required extra safety measures and Meridian was concerned survey equipment could be pulled into the hydro system.
Our Expertise
Fox and Associates utilised our advanced surveying capabilities:
Unmanned Surface Vessels (USVs): Survey-grade GPS and sonar, collected precise underwater data in difficult to access spaces.
UAV Surveying: Our UAVs captured LiDAR and aerial imagery of above-water and near-surface sections.
Data Integration: Our team merged datasets into a single3D model for analysis.
Expert Analysis: We compared the new model against design cross-sections to spot erosion or material buildup.
The Solution
We surveyed 2.4 km of canal using both our BathyCat and Jettec USVs. Our original USV BathyCat was able to be used during low flows while the newer Jettec jet boat provides greater capability in faster flowing water conditions. Both vessels remained tethered for safety.
Our UAV technology captured LiDAR and aerial imagery complementing sonar results despite the glacial sediment clouding the water.
All data sources were combined to produce a 3D model of the canal, including salmon rafts and other features for further analysis.
The Result
By aligning our 3D model with Meridian’s original design cross-section, we clearly identified any areas of potential erosion or accretion (accumulation).
The final outputs:
- Delivered accurate, geo-referenced visualisation of the canal bed.
- Highlighted areas where the liner may need attention or more detailed visual inspection.
- Provided insight into the potential impact of salmon farm rafts.
- Gave Meridian confidence to make informed, cost-effective decisions.
Meridian was highly impressed with the quality and clarity of the deliverables. This project showed the Fox approach in action, solving complex problems with innovative, practical, and cost-effective technology.
We’re proud to support the legacy of New Zealand’s vital infrastructure. We’ll be ready when the next canal calls.
To learn more about this project, read our blog Surveying the Ōhau Canal.
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