The Royal New Zealand Navy's underwater screening equipment has been used as part of a conservation project for the first time in Wellington.
Today a team of hydrographers used an underwater autonomous vehicle to map the bottom of the lower lake at Wellington urban eco-sanctuary, Zealandia.
"This was a pipe dream I could never have imagined that we could have the Navy here today helping us," Zealandia conservation manager Danielle Shanahan said.
It happened after Alan Peck, the volunteer skipper of Zealandia's lake tour boat, heard Ms Shanahan's conundrum of not knowing how to determine what potential objects lay below the lake's surface, which could interfere with pest control efforts to restore the lake.
"He used to work for the Navy, he said, 'Oh, I can help you with that,'"Ms Shanahan said.
Mr Peck got in touch with his former workplace and the request was accepted.
"They didn't have a UAV when I was in the Navy, I retired in 2005," Mr Peck said.
"I had no idea I would reconnect with the Navy through Zealandia, that's just quite a coincidence."
The Royal New Zealand Navy's Commander Robert Ochtman-Corfe said the mission provided a unique training exercise with real-life effects for helping Zealandia restore the lake.
"The guys have learnt how to operate in this restrained environment in fresh water," he said.
UAV's are normally used by the Navy to determine if there’s any objects like bombs or rocks in the path of a vessel.
"It puts out a very detailed sonar picture so we can find things down to about 10 centimetres in diameter," he said.
The waters of the lake is the catchment area for Kaiwharawhara Stream, Wellington's largest stream system.
"It's one of the only catchments that's open to the harbour so it still allows fish to migrate up into it," Danielle Shanahan.
The lake is not in a good state, with up to 30,000 perch fish believed to be affecting the water quality by eating the organisms that normally control algae in the lake, Ms Shanahan said.
"There's a lot of different options at our disposal but we need to have good information so that we can make the best plans possible.
"That might be for example electric fishing, a whole range of options," she said.
What's believed to be a mine shaft was found below the surface by the Navy today.
The lake's the former site of a 19th century gold mine.
It was later flooded for use as a water supply for Wellington before being decommissioned, then becoming a protected lake as an area of historic significance for the capital.
The images of the lake floor captured today is the first time there’s been a record of the area in more than 100 years.
Ms Shanahan said it’s an important milestone in Zealandia’s ongoing project, from Sanctuary to Sea, which aims to increase native species in the Kaiwharawhara Stream and improve the water quality.
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