Once a favourite Hawke's Bay destination, Lake Tutira is in a bad way
The shady reserve overlooking Lake Tutira has been a favourite rest stop for generations of travellers making the journey between Napier and Wairoa.
But pull off State Highway 2 beside the picturesque lake these days and you're hit with an offensive odour reminiscent of a milking shed floor before it's been hosed down.
A trip to the water's edge delivers another unpleasant experience. The once-swimable lake is murky and uninviting, and covered in a layer of green slime.
"It's a shame the lake has got to this point," says Hemi Poutu, a Napier resident who has stopped for a break on his journey.
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Poutu, who recalls swimming at Tutira years ago, says he can smell the pollution from several kilometres down the road.
Now signs warn against swimming, or eating fish caught in the lake.
Last month – not for the first time – the Hawke's Bay District Health Board confirmed a toxic bloom at the lake and warned visitors to avoid contact with the water and to keep animals away.
In recent times several instances of mass deaths of trout and eels in the lake have been reported.
One such event, in January last year, was blamed on a combination of high water temperatures and "atypically low" dissolved oxygen levels.
Another spate of eel deaths late last year was thought to be related to the release of ammonia from organic material accumulated on the lake floor.
A number of factors have led to the lake's degradation. It receives runoff from farms in the catchment and appears to be more susceptible to toxic algal blooms after inundations from nutrient-rich flood waters following heavy rain.
Hawke's Bay Regional Council environmental scientist Andy Hicks said the council was working on a strategy to improve water quality in the lake after completing a major ecological modelling project with Waikato University using years of water quality data.
Rather than a "knee-jerk reaction to the latest bloom" the council was looking at long-term solutions including building sediment traps to prevent nutrients entering the lake, Hicks said.
Another option was a "bubbler" that would keep the lake in a "well oxygenated state" and prevent the worst of the blooms.
"We're also going to need a lot of time because this problem didn't happen overnight and it's not going to go away over night."
Fish & Game Hawke's Bay regional manager Mark Venman said the lake was in "a sorry state at the moment" and the organisation was supportive of plans to remedy the problem.
Given last year's fish deaths, Fish & Game had been "hesitant" to continue with its usual practice of releasing yearling trout into the lake but went ahead in October and November because "we wanted some fish in there," Venman said.
Since then there had been no confirmed mass fish deaths due to the conditions and he was hopeful that once once a plan was agreed on to rehabilitate the lake, it would eventually revert to being a good fishing spot.