Cutwater Road wetland project

Toi Moana Bay of Plenty Regional Council and iwi collective Te Wahapū o Waihī have a shared vision of creating a ‘korowai around the Waihī Estuary’ – a protective buffer of wetlands designed to help restore the health of this highly degraded area.

The first step in achieving this vision was the purchase of a 109ha Cutwater Road farm next to the Waihī Estuary in June 2023. The land was subdivided – 79ha was sold to a neighbouring farmer, who has an interest in contributing to estuarine health, while the remaining 30ha will be converted into wetland.

Initial purchase of the land was funded 50% by Regional Council and 50% from Te Wahapū o Waihī through the Ministry for the Environment’s Freshwater Improvement Fund.

The design for the wetland involves creating a 27ha freshwater treatment wetland and 3ha tidal coastal wetland. Wetlands are incredibly important ecosystems, and provide numerous environmental and cultural benefits. Once complete, these wetlands will help improve water quality and biodiversity, contribute to climate change mitigation and adaptation outcomes through carbon storage, and support the cultural and recreational values of the area.

Why are we doing this?

The Waihī Estuary has been identified as one of the most degraded in the country, due to decades of wetland drainage, river channelisation, land use change and contaminated runoff throughout the 35,000ha catchment.

Monitoring and modelling work shows it needs substantial reductions of 40-60% in sediment, nutrients and pathogens, plus in-estuary interventions, to achieve a state of moderate health.

Modelling of the area was done by DHI Water and Environment, who found that providing wider coastal wetland buffers was one of the key interventions required to improve estuarine health. By increasing the capacity of these buffers, this allows the tide to come in and flush the estuary, cleaning it of excess contaminants in the process.

Alongside this, reductions in freshwater-borne contaminants through implementation of good farming, forestry and horticultural practices are equally important. Regional Council staff are currently working with 37 landowners in the Waihī Estuary catchment on active Environmental Programmes and are in the process of negotiating with a further 25. In addition to the landowner work, there are numerous contributions being made by others, including community groups Maketū Ōngātoro Wetlands Society and Wai Kōkopu Inc.

What’s been done?

In 2024, the Nature Conservancy Aotearoa completed blue carbon research on this site as part of a pilot programme. The results will provide baseline data to help us measure the project’s long-term ability to store carbon and contribute to climate mitigation.

What’s happening now?

Wetland creation began November 2024

Construction will include creating two types of wetlands.

• 27ha freshwater treatment wetland: We will be installing a pump station to pump water from the 617ha catchment through the wetland to filter sediment and nutrients before reaching the estuary.
• Tidal coastal wetland: We’ll be installing a rock rip rap channel to provide greater capacity, and allow the tide to come in and flush the estuary.

This work also involves creating earth bunds within and around the wetlands to contain water in the wetland, slow its flow, and increase filtration of sediment and nutrients.