No Christmas cheer for Hutt River users

Wednesday, 20 December 2017

Toxic Algae in the Hutt River

The Hutt River will remain off limits to swimmers - and dogs - until after Christmas because of potentially fatal toxic algae levels.

However the Pakuratahi River at Kaitoke is again open for recreational use and the Greater Wellington Regional Council is hopeful a Hutt Valley all-clear may follow in the new year.

The Pakuratahi River, which flows into the Hutt at the Kaitoke Regional Park, has experienced a gradual disappearance of the algae that had seen it off limits since late last month.

Kaitoke Regional Park where the Pakuratahi River has been given a swimming all clear.

The river's toxic turnaround represents a 'slight mystery', regional council senior environmental scientist Mark Heath said.

**READ MORE:

Large dark patches of toxic algae can be seen on the Hutt River.

* Swimmers told to avoid Hutt River after discovery of 'potentially fatal' toxic algae

* Dog owners warned as toxic algae 'red flags' raised for Hutt River

* Warning after toxic algal bloom found in Timaru creek**

'We are learning about toxic algae all the time and finding out more and more, especially through having such a long period without rain.

'We are uncertain why we are seeing a decline of algae in the Pakuratahi and, to a lesser degree, in the Hutt River.'

Heath said the 'rather large' toxic algae bloom had probably contributed to its own decline.

Algae needed nutrients to survive and the bloom had perhaps exhausted its supply.

'As a result I believe the algae has become very unstable with bits breaking free of the riverbed and floating down the river.'

There had been only limited rain in the Kaitoke area.

'It wasn't what we call a flushing flow but with that instability already there it was enough to move it. It is now well below our safety guidelines.'

While the new readings allow for swimming in the Pakuratahi, the Hutt River remains a no-go.

'Toxic algae is still in the Hutt River and above guideline levels, meaning the health warnings remain in place.'

The next water testing and update on whether it is safe to swim will be after Christmas, Heath said. 'It is so sad this is happening at the peak of summer, the river is our crown jewel really and we can't use it.

'We want people to know that but also be aware they can safely use the Hutt's four main tributaries.'

Along with the Pakuratahi these are Akatarawa, Whakatikei and Mangaroa.

* For up-to-date information on toxic algae and an interactive map see: gw.govt.nz/is-it-safe-to-swim/

THE STATE OF OUR RIVERS:

* Hutt River: Remains unsafe.

* Ōtaki and Waikanae Rivers: Both have low levels of toxic algae and are safe for swimming. They have large amounts of harmless green and diatom algae.

* Akatarawa, Whakatikei and Mangaroa Rivers: Safe for swimming but keep an eye out for toxic algae.

* Pakuratahi River: Safe until where it joins with the Hutt River.

* Petone Beach: Safe to swim. Marine 'macro algae' is present but completely safe.