Frustration is slowly turning to anger for residents at Lake Rotoiti who say lakeweed is ruining the lake and not enough is being done about it.

But the Bay of Plenty Regional Council says it has a weed harvester in the area at the moment and it is doing what it can to stay on top of the problem.

Some Okawa Bay residents say the problem with lakeweed in the bay and other parts of the lake is now out of control and large masses of floating weed were fouling up boats' propellers, keels and rudders, and could trap swimmers.

The issue was highlighted on the weekend when members of the Lake Rotoiti Classic and Wooden Boat Association could not navigate their boats around Okawa Bay because there was so much lakeweed.


Association member Fraser Wilson, who lives at Okere, said for the first time in 19 years the parade could not get into Okawa Bay.

"They had the weed harvester in there at the last minute, but it did nothing."

He said there were masses of weed 5m to 6m long and 2m to 3m wide in the bay, stopping boats in their tracks and the situation was becoming unsafe.

"If a child or someone in a canoe fell in they could easily get caught and not be able to swim out."

Tonnes of lakeweed has built up in Okawa Bay, leaving behind a bad smell for residents. Photo / Stephen Parker
Tonnes of lakeweed has built up in Okawa Bay, leaving behind a bad smell for residents. Photo / Stephen Parker

Okawa Bay residents spoken to by the Rotorua Daily Post said as the lake water had cleared up more sunlight was growing the weed at an accelerated rate

Chairman of the Lake Water Quality Society and Okawa Bay resident Don Atkinson said there was a solution to the masses of hornwort and oxygen weed clogging up the lake.

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"The bay is absolutely stuffed up and is really unusable. We have been asking as a community for at least the last three years to have the scientifically proven herbicide Endothall used to clean it up," he said.

"Nil progress has been made on this important issue and it will get to the stage when we can't use bays or beaches. It's ridiculous."

Okawa Bay resident Richard Amery said he and others were upset at the lake's condition.

"We are constantly seeing yachts and jetskis getting stuck out in the bay ... there is no collection system for the tonnes of weed that mounts up on the lake edge where it decomposes and turns into a sort of black sewage that stinks to high heaven," he said.

Te Tatau o Te Arawa Board chairman and Okawa Bay resident Te Taru White agreed the problem was getting worse.

"In my view the lake is dying. The diversion wall has done well to reduce the nutrient problem but Okawa Bay is another issue and needs to be fixed."

Regional council lakes operations manager Andy Bruere said he was aware of the issue.

He said a weed harvester had been operating for nearly a week, including a couple of days before the Wooden Boat Parade. It would be there for two weeks.

"It's disappointing people are not happy because people we have talked to are happy the work has been started."

Mr Bruere said the regional council had herbicides it could use but history had shown when they were used in a closed bay, an algal bloom appeared in the water months later.

He said the regional council was in the process of applying for a resource consent to use Endothall but it felt the weed harvester was the better option