Wave barrier aims to protect plants at Te Waihora

An important step in the restoration of Te Waihora/Lake Ellesmere is currently under way.

There is key progress on a significant science project for the Whakaora Te Waihora restoration programme, with NIWA installing a 100-metre wave barrier on the south-eastern side of the lake to enable submerged plants, known as macrophytes, to become established. 

Macrophytes are multi-tasking plants that buffer waves, improve water quality and provide diverse habitats for fish. Massive macrophyte beds previously grew in the lake but declined and disappeared in the 1960s. The decline was exacerbated by the Wahine storm in 1968 that tore extensive plantation from the lake.

This is the first time a barrier of this type has been installed in a New Zealand lake and has been purpose-built by NIWA staff through funding from Whakaora Te Waihora. The barrier comprises 59 New Zealand Oregon logs, each 10 metres long.

The logs are arranged three deep side-by-side, with the rest placed in a triangular pattern to brace the structure which is being anchored to the lake bed in several places. A cable runs the length of the barrier to hold it in place.

The barrier will enable the young, transplanted macrophytes to become established so they can help prevent erosion and improve water quality.

The transplanted macrophytes will come from a culture nursery that has been established at Taumutu on land leased from the owner.  Whānau from Taumutu Marae have offered extensive local knowledge on the lake and its history and have shown researchers the best places to source seeds and plants, including from the neighbouring  Halswell River.

NIWA freshwater ecologist Mary de Winton is leading the macrophyte restoration project, believed to be the only one of its type in the world.

“We’ve chosen the sites we think will give them the best chance of survival,” she said. “If we can get them to re-establish long term, we are confident they will have significant benefits for the future of the lake.

“Even if the beds fail to re-establish long term, we hope we may better understand why they never recovered naturally and why they struggle to survive in current conditions.

Te Waihora is New Zealand’s fifth largest lake and one of our most polluted. It is a taonga for Ngāi Tahu as well as an important link in the chain of coastal lagoons and estuaries along the east coast of the South Island.

It has been described as the most important wetland habitat of its type in New Zealand. It is important for migratory wader bird species and threatened indigenous species. It has a high bird population of diverse species and also supports many indigenous fish species.

Whakaora Te Waihora is a programme to restore the cultural and ecological values of Te Waihora, and is co-governed by Ngāi Tahu, Environment Canterbury, the Ministry of the Environment and Selwyn District Council. It is expected it will take at least two generations, or 35 years, to restore and rejuvenate the lake.

Programme Implementation Manager David Murphy said he was very pleased to see the macrophyte project reach this important milestone.

”This project has an important place in the Whakaora Te Waihora  programme as a whole and the science programme in particular,” he said. “It is very pleasing to see the progress that has been made to get us to this point.” 

For more background on this project and Whakaora Te Waihora, go to http://tewaihora.org/breaking-new-ground/.

For further information contact:

Angus McLeod, Senior Communications Advisor, Environment Canterbury, 0275 497 691

Kurt McLauchlan, Communications Advisor, Te Rūnanga o Ngāi Tahu, 027 322 0806

Susan Pepperell, Senior Media Advisor, NIWA, 027 839 0730