FAQs

The Project involves construction of a hybrid engineered and restoration focused natural wetland system to the south of Punahau Lake Horowhenua. The hybrid design involves more natural and less engineered wetlands closer to Punahau, and engineered wetlands in the elevated areas of the site.

The engineered part of the wetland still appears ‘natural’ as passive wetlands, but provide higher levels of treatment with a similar footprint.
 

The Project site is located approximately 3km west of the township of Taitoko (Levin), 6km from the sea (Hōkio Beach) and between Punahau and Lake Waiwiri. The site is accessed via Hōkio Beach Road near the north-east side of the site. The proposed wetland site has previously operated as a 142 ha dairy farm.
 

The Project has been designed to enhance the water quality of Punahau through the construction of engineered treatment wetlands and restoration of previously drained natural wetlands in the Arawhata Stream catchment. Presently, Punahau is one of the most degraded lakes in Aotearoa New Zealand. The Project will also enhance the cultural and ecological values of Punahau and its surrounds.
 

The water quality of Punahau is very poor.

Of the Lake’s tributary inflows, the Arawhata Stream contributes the largest amount of nitrogen to Punahau. Concentrations of nitrate in the Arawhata Stream are higher than the drinking water standard and are likely toxic to a range of fish species.

The Arawhata Stream’s median nitrogen concentration (total oxidised nitrogen) is the second highest in New Zealand and the highest in the region. The Arawhata Stream is also the single largest source of sediment and phosphorus to Punahau.

This Project is a continuation of restoration efforts at Punahau, alongside the Horowhenua 11 Part Reservation Trust (the Lake Trust) to improve water quality of the lake.
 

A Governance Group to oversee the project has been established, with representation from Horizons Regional Council, Horowhenua District Council, the Lake Trust, Muaūpoko Tribal Authority, Te Runanga o Raukawa, and Ministry for the Environment.
 

It is proposed that the wetland complex will be developed over three stages. Resource consents for the first two stages are currently being sought in the first instance, with works involved in the third stage to be authorised separately in the future. Construction of the first stage is presently programmed to commence in the summer of 2025/26.

Stage One of the Project involves constructing sediment basins, modifications to existing drainage systems on the site, including removal of some drains, deepening and widening of other drains and planting of native plants.

Funding for the project has been provided through the Government’s Jobs for Nature programme. Horizons has been contracted by the Ministry for the Environment to deliver the project.

Horizons is committing additional funds and ‘in-kind’ support to the project.
 

The Project will result in an overall net environmental improvement relative to the existing environment, including positive effects on water quality, cultural, and ecosystem health values.

The Project will result in substantial nutrient reductions (sediment, nitrogen and phosphorous) in the Arawhata Stream catchment as the wetland acts as a capture and filtering system, and in turn within Punahau. Overall ecosystem health will be enhanced through the creation of a new wetland habitat and reduced sediment and nutrient loads within the Lake.

It is anticipated that the equivalent of 45 FTEs will be employed in association with the Project over the period ending in mid-2026.
 

The constructed wetland concept design has a sediment pond where the Arawhata Stream currently enters the wetland site. This will allow the larger sized sediment particles to drop from the water column before entering the wetland complex.

Sediment traps are also planned for the Wheelan and Joblins road drains that enter the property.

The modelled effectiveness of the wetland complex has indicated substantial reductions in sediment, nitrogen and phosphorus. This modelling has been completed using water quality and quantity data collected from the Arawhata Stream and other relevant waterways on the property. The modelling outputs will be further refined during the next design phase for the wetland. View the modelling report for more information.
 

No, the current sediment trap is in place to remove sediment from the Arawhata Stream in high flow events.

The proposed wetland will remove sediment in sediment traps prior to the Arawhata Stream entering the wetland. The main objective of the wetland is to remove nitrogen from the water. The Arawhata Stream has some of the highest nitrogen concentrations recorded in the Horizons Region and this has a detrimental impact on Punahau.
 

This land will continue to be farmed in some capacity until Stage Two and Stage Three are completed. From 1 of June 2023 the farm is no longer a dairy farm. This will reduce the level of nutrients that are leaching from the property. The farm will be limited to a dry stock and a cut and carry farm system. 
 

Stage One of the wetland will not meet the requirements for native carbon farming as the species found in this kind of environment do not grow large (tall) enough. The forest species proposed as part of Stage Three could meet the requirements for native carbon farming. This will be considered at the time of construction of Stage Three.
 

Costings for on-going operation and maintenance will be refined once detailed design is undertaken. The refined costings to enable ongoing maintenance will be factored into the implementation program.
 

There has been general support of a trail between Punahau Lake Horowhenua and Lake Waiwiri. The concept proposal has incorporated a walkway into Stage Three of the design.
 

Plants will be eco-sourced (sourced locally) and the final selection of species will be decided with iwi input. Preference is for species that were historically found across the Project site, in surrounding areas like Arawhata bush block and Waiwiri Reserve, and within the ecological district. The plants will need to be sourced from a range of native plant nurseries in the Horowhenua area due to the number of plants that will be needed over the life of the Project.