The council's works group manager, Hamish Fraser, said the boats could cut weed to 1m underwater.
"They cut the invert of the stream, which is basically the bed of the stream," he said. "There is no other efficient way of removing the weed – it can't be reached by an excavator and it would eventually clog the waterway."
In addition to their own rivers, the council cuts weeds for the Greater Wellington Regional Council at Otaki.
"We have in the past done cutting in Auckland for the Auckland City Council, and also for the likes of some smaller private clients that have ponds.
"Originally the regional council purchased a weed boat from England, in the 1970s.
"That was a very primitive sort of a boat and a lot bigger than these. Through the past 30 years the regional council has developed these boats back at their workshop in Guppy Rd, moving to this aluminum-style weed boat, which are manoeuvrable and stable."
The paddles and cutting bar of the boats are run by a hydraulic pump, powered by a diesel motor.
"The cutting bar is basically a series of teeth that move backwards and forwards - a bit like an old sickle mover. They reciprocate and cut the base of the weed.
"The boats are a fairly one-off specialist piece of equipment, but there is a demand for them throughout New Zealand."
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