ASR - A Global Partner for the Sustainable Management of Coastal and Marine Resources

Kaipara Harbour

Location: Kaipara Harbour, New Zealand

Type of Project: Field Measurements, Numerical Modelling

Client: CREST Energy Ltd, New Zealand

ASR Projects- Kaipara Harbour

Anticlockwise from the top left: ASR scientists conducting a night-time instrument deployment; the tidal range during the field program; the modeled peak ebb tide velocity in the Kaipara Harbour.

Project Overview:

Due to the strong tidal flows at the entrance to Kaipara Harbour, the largest estuary in New Zealand, this site is a potential location for electricity generation by tidal currents. The increasing demand and price of electricity, as well as the maturing technology in tidal current energy extraction devices, justified the investment and further investigation of this resource. Crest Energy Ltd commissioned ASR Ltd to undertake preliminary field data collection to assess the feasibility of developing tidal energy in the Kaipara Harbour.

Project Outcomes:

A short-term, intensive fieldwork programme was undertaken to measure current velocities and identify potential locations for possible tidal energy extraction devices in the Kaipara Harbour. Data was collected primarily with an ADP (Acoustic Doppler Profiler), which measures current speed and direction throughout the water column. In addition, bathymetry data, seabed video and grab samples (both sediment and benthic organisms) were collected.

The fieldwork program was followed by a numerical modelling study of the Harbour hydrodynamics. A 2D hydrodynamic numerical model of the Kaipara Harbour was calibrated and validated based on the data collected in the field study. The modelling quantified the intensity and duration of currents within areas of the harbour targeted for energy extraction, as well as the impacts of tidal generators on existing current circulation and harbour sedimentation.

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