Sediment still a concern for Waituna Lagoon's health

Wednesday, 6 May 2020

A five-year project to restore the Waituna Lagoon has spent $9.3 million so far but it may not be enough to address sediment issues.

In 2018, The Whakamana te Waituna Charitable Trust and its partners received $13.2m from the Freshwater Improvement Fund, to be allocated over five years.

Waituna Lagoon was one of the first wetlands in New Zealand to be recognised by RAMSAR as a site of significance and identified as taonga (treasure) to Ngāi Tahu for traditional food gathering practices (mahinga kai).

However, according to Mokotua dairy farmer Joanne Crack​, '$13 million is like putting a band-aid on a bullet wound, and not bothering to take the bullet out.'

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The issues around Waituna Lagoon were complex and while the trust was focused on improving the lagoon, $13m was never enough to get the fix they wanted, Crack said.

While there was growth in ruppia and the lagoon was fishing well, the decade-long issue of silt had not been addressed, she said.

'As long as that silt is still there then no amount of band-aids will bring the necessary result.' 

Fonterra sustainable dairy advisor Cain Duncan​, who is working alongside the trust, said there was not enough funding within the existing budgets to deal with sediment and nutrient levels for the entire lagoon.

The trust could seek further funding at a later date but its first priority was to develop a plan for how it would address sediment issues, Duncan said.

A sediment and nutrient reduction project was likely to be completed by the end of the year, he said.

The project would be in consultation with farmers to decide if a sediment plan was to be managed at a farm level or a catchment level.

Duncan did not know how much of the $13m had been spent dealing with sediment issues for the lagoon.

Living Water South Island manager and Department of Conservation freshwater science lead at Waituna Lagoon Nicki Atkinson​ said macro algae levels were quiet in the last year recorded, because of high nutrient levels coming into the catchment, but would be a focus for the project going forward.

However, the growth of the native aquatic plant ruppia had been significant in the lagoon over the past two years which was an important factor in determining the health of the wetland, Atkinson said.

The lagoon was in a vulnerable state but it was also in a reasonably healthy state, which was noted by the fact it had not been dominated by algae over ruppia, she said.

The improvement in ruppia growth in the past two years was due to the lagoon being closed during the spring/summer period, she said.

Trust chairman Dean Whaanga​ said while the ruppia growth had been going well, there was still work to be done with high nutrient inputs that were coming from surrounding land.

Although the impacts on the land would remain, the purchase of surrounding land with the funding it had received would enable the trust to manage those impacts better, Whaanga said.

'We are hoping that all the work we are doing as a community, with Wakamana te Waituna partners and farmers are contributing to a better health and wellbeing, not just of the lagoon but of the waterways as a whole.'