MANGAONUKU - WETLAND CREATION AND MONITORING
SUMMARY
In July 2025, the Mangaonuku sub-catchment used a TLC Demonstration Grant to install a constructed wetland at the lower end of the Mangaonuku sub-catchment as part of a locally led effort to improve water quality.
Water testing at the site began in January 2026 and results are shared below.
BACKGROUND
The site, fed by a spring with elevated nitrate levels, was identified as a priority following earlier water testing and the Big Picture catchment planning work completed in late 2024.
The aim was to trial whether a small wetland could act as a natural filter – reducing the amount of Dissolved Inorganic Nitrogen (DIN) entering the Mangaonuku Stream. The project reflects growing landowner interest in using practical, on-farm tools like wetlands to support catchment health.
Plants were chosen to provide filtering, stabilise the soil, and restore native habitat. Nearly 1,400 native wetland plants were planted, including: mānuka, cabbage trees, tenax flax, carex secta, umbrella sedge, oioi, mixed native species.
WATER TESTING
Monthly water testing is being carried out by Water Sense Te Wai Tikanga above and below the wetland to monitor its impact on water quality and nitrogen levels.
The monitoring programme will help determine:
-
Whether the wetland is reducing dissolved inorganic nitrogen (DIN) as expected.
-
Whether similar wetlands could be effective in other spring-fed areas throughout the catchment
If successful, this site could provide a model for future wetland development, demonstrating how targeted, practical interventions can improve water quality and support healthier waterways.
You can view a summary of water testing results from January - June 2026 here.
RESULTS
WITH THANKS
The project was made possible through a TLC Demonstration Grant, with support and involvement from:
-
The Reynolds family – landowners and project hosts
-
Nathan Burkepile (NZ Landcare Trust) – design and technical input
-
Central Natives – plant supply and advice
-
Mauri Oho – planting crew
FURTHER INFORMATION & CONTACT
To find out more about the Mangaonuku sub-catchment, head to the Mangaonuku sub-catchment page on this site.
To get in touch, please contact TLC Catchment Coordinator Mark Falconer
Email: tukicoordinator@gmail.com
Phone: 0277559357