Lake Horowhenua weed harvesting trial to begin this year

At Horizons Regional Council meeting today, councillors recommended the progression of the Lake Horowhenua weed harvesting project to improve the lake’s water quality.

Horizons chair Rachel Keedwell says that weed harvesting will help restore pride and mana to Lake Horowhenua and enhance its social, cultural, environmental and economical values. 
“Today’s decision progresses a generational opportunity to improve the lake’s health,” says Cr Keedwell.
“Council has approved a further budget of $223,600 to enable the lake weed harvesting project to progress in the 2021-22 financial year. Having the trial start this Spring will be a significant milestone.”
Lake Horowhenua Trust Chair Clinton Hemana says the weed harvesting project is an important step forward in a very long journey.  
“On behalf of the Lake owners, the Lake Trust is very pleased that Horizons Councillors have voted to continue the Lake Horowhenua weed harvesting project this year,” says Mr Hemana.  
“As the Tangata Whenua we are looking forward to gaining the knowledge that will come from this phase of the project and to continuing the impetus towards the return of the mauri and mana of the Lake that we are working towards under the partnership of the Lake Horowhenua Accord with Horizons, Horowhenua District Council and the Muaupoko Tribal Authority.”
Cr Keedwell says harvesting the lake weed has been identified as a key action to reduce toxicity of Lake Horowhenua and to increase the frequency the lake is suitable for recreational use. 
“Introduced lake weeds have a significant impact on the chemistry and internal processes, including impacting the pH of the lake. The impact on pH can influence the occurrence and frequency of ammonia concentrations in the lake that can be toxic to fish and other aquatic life,” says Cr Keedwell.
“The lake weed also influences the occurrence of cyanobacterial blooms which can also impact on both aquatic life as well as suitability of the lake and the downstream estuary and coastal environments for recreational use.
“The approved budget is for costs that have been encountered for the trial year and include one-off set up costs, costs to meet consent conditions, costs related to disposal of the weed, security costs, and costs for Tangata Tiaki involvement for the Lake Horowhenua Trust and Muaūpoko Tribal Authority, potential legal costs, compliance monitoring costs and the costs of the harvesting itself.”
In addition to the sediment trap that was installed in 2017, weed harvesting is viewed as a key restoration measure to reduce toxicity in the lake and is predicted by NIWA to move four of the five key water quality parameters to above the national bottom lines (Ammonia, Cyanobacteria, Chlorophyll a, and Total Phosphorus).
The lake weed harvesting programme has a phased introduction over its first two years. A trial required by resource consent conditions in the first year will inform a fuller programme of harvesting in future years if certain resource consent conditions are met.
Other planned interventions include stormwater improvements that Horowhenua District Council have committed over $6.67 million for in their Long-term Plan.
Horowhenua mayor Bernie Wanden says that on many occasions the District Council has asked the community what their top priorities are.
“The health and wellbeing of Lake Horowhenua consistently comes out as a resounding priority and as such, Council remains committed to the aspirations of the Lake owners, Lake Trust, and the Lake Accord and its partners,” says mayor Wanden. 
“Council is pleased that Horizons has committed to the weed harvesting programme for this year and are ready to support this next step in the programme of works and beyond.”
Horizons and the Ministry for the Environment have also committed $12.5 million to the Lake Horowhenua water quality interventions Jobs for Nature project. The Jobs for Nature project is phase one of a longer term work programme to establish a wetland complex to reduce sediment and nutrient inputs to the lake.
It is noted that the science indicates that neither the wetland complex project nor stormwater project will address the in-lake processes that the lake weed harvesting project targets. 
The full Lake Horowhenua weed harvesting agenda items can be found here and here.