Oceanographic processes, Rarotonga, Cook Islands
Last week WRL coastal engineers Matt Blacka and Chris Drummond were again working on Rarotonga in the Cook Islands, continuing our investigations on the Mei Te Vai Ki Te Vai project. This round of field work focussed on gathering data for oceanographic processes outside of the lagoon along the south-eastern coast of Rarotonga.
The team worked in partnership with scientists and crew from the Cook Islands Ministry of Marine Resources (MMR), to collect some key data sets on nearshore ocean currents and mixing processes. This information is essential to help inform the feasibility of an ocean outfall as a long-term solution for disposal of treated wastewater on Rarotonga.
The data collection program included dye tracing and current profiling at four locations along the coast, and is the first of its kind undertaken in the Cook Islands. A fluorometric tracer dye, Rhodamine WT, was dropped at specific locations in the ocean, and the concentration and movement of the dye plume measured for about 1/2 to 1 hour at each site. An Acoustic Doppler Current Profiler (ADCP) was also used to profile currents around each of the sites, and to understand how the currents vary at different depths and locations.
The data sets from these field investigations will be used to better understand the potential mixing and transport of wastewater from an ocean outfall, and to help design an outfall to have minimal environmental impacts.
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