Wetland bringing back a piece of native Canterbury

A landmark wetland project in Canterbury is now almost complete, creating a new habitat for native plants and animals in a part of the region where once wetlands abounded.

In May, as COVID-19 restrictions began to be lifted, contractors were able to complete the final earthworks for the Whakaora Te Ahuriri constructed wetland, located on the Little River Rail Trail between Tai Tapu and Motukārara.

A significant step for Te Waihora / Lake Ellesmere programme

The Co-Governors of Te Waihora / Lake Ellesmere (Environment Canterbury, Te Rūnanga o Ngāi Tahu, Selwyn District Council, Christchurch City Council and the Department of Conservation) acknowledged the milestone.

Co-Chairs Lisa Tumahai (Te Rūnanga o Ngāi Tahu) and Jenny Hughey (Environment Canterbury) said this was another significant step in an important part of the Whakaora Te Waihora programme designed to help achieve long-term goals for the lake.

“One of our predecessors, Steve Lowndes, said some time ago he couldn’t wait to see the completed wetland,” the Co-Chairs said. “It’s very exciting to see that this time isn’t too far away now and that good progress continues to be made despite all the challenges everyone has been facing recently.”

Final works included the removal of a temporary earthen dam between the culvert exiting the wetland and the main channel of the Huritini (Halswell River), reconnecting the wetland with the river and making it fully operational.

Netting installed to protect plants from being uprooted by pūkeko before becoming established is still in place but will be removed in the coming weeks.

Wetland to act as natural filter

Low rainfall this year has left low water levels in Ahuriri Lagoon and flow in the Huritini / Halswell River, but when rain returns, the wetland will be seen in its full glory.

The wetland works as a natural filter for the Huritini, which has degraded water quality from both urban and rural sources. Water leaves the main branch of the river and flows through part of the original channel, passing alongside the Little River Rail Trail in a section newly planted with native seedlings, before entering the top of the wetland.

There it meanders through an area containing more than 80,000 aquatic plants that act as a filter to remove nitrates and other contaminants, before rejoining the river, which flows into Te Waihora / Lake Ellesmere.

Restoring the ecosystem

The site is already proving popular with native birdlife, and a Mātauranga Māori monitoring programme is surveying fish numbers to establish a cultural health index.

This area was once an important mahinga kai site for local rūnanga, and it’s hoped that the Whakaora Te Ahuriri constructed wetland can help restore mahinga kai values to the area.

The creation of a constructed wetland at Ahuriri Lagoon is a major aspect of the wider Whakaora Te Waihora restoration programme, which aims to restore the mauri and ecosystem of Te Waihora / Lake Ellesmere.

For more information on Whakaora Te Waihora, visit the co-governance website.