A large wetland or several smaller ones in the Arawhata Stream catchment may solve all of Lake Punahau/Horowhenua's problems, eventually.
Horizons Regional Council has received millions from the Government to study options, buy land and implement whatever is best for the district's water quality.
Nitrogen, phosphorous and sediment are the big issues for Lake Punahau/Horowhenua and a lot comes through the Arawhata Stream into the lake.
While a number of vegetable growers in that catchment have already achieved significant reduction in nitrate leaching into nearby streams and a number of sediment traps have been put in near lake inlets, there is much more that needs to be done.
The catchment also contains a number of other streams and stormwater drains that feed directly or indirectly into the Arawhata Stream.
The idea has come from a large group of interested parties which formed the Arawhata Wetland Alliance last year.
While Horizons in principal agreed with the proposed plan for a wetland, the funding application was put together in a bit of a hurry, initially by HDC and was then handed to Horizons who modified the application, but much detail still needs to be worked out.
Jon Roygard, Horizons ' natural resources and partnerships manager, told regional councillors this week that the idea for a wetland has come from a local group of people who have formed an alliance to try and deal with multiple issues affecting the water quality in the Arawhata Stream, which runs into Lake Punahau/Horowhenua.
That group includes growers, representatives of local iwi Muaūpoko, councils and a few others and their aim is to improve water quality in the lake. Initially some horticultural growers, some iwi and the district council put a plan together and Horowhenua District Council applied to the Crown Infrastructure fund for money.
After further discussions with local growers and the alliance the decision was made for Horizons to take over the application. Horizons combines the wetland concept with its broader water quality improvement programme. The project will take four years and is expected to cost $12 million.
Roygard said he expects the planning process to take up the first few months and this will include some intense science. He said there were multiple issues that need looking at such as groundwater as well as water allocations current in place.
"The first six months will be extremely busy," he said.
Ten designs for a wetland have already been commissioned and Horticultural growers have committed some funding to this.
Roygard said the application builds on work already in progress and offers a bigger picture approach.
"We can now look at the catchment as a whole. At the moment things are happening at outlets into the lake but this plan will allow us to go and do work much further upstream," he told regional councillors.
"We are not focusing on just one piece of land at this time. Some experts say one big wetland would be best while others advocate for several smaller ones. What you want to deal with decides how a wetland is being designed."
In the first year a co-ordinator will be appointed and an advisory group will be put together, the latter is a requirement from the Ministry for the Environment for the project.
"We are committed to working with the community, including growers and iwi on this," he said.
Community planting days are anticipated.
Monitoring and water quality will be a big part of this project and consent will need to be obtained for any work anticipated once de research has been done.
Design of the wetland system will depend on local conditions and on what needs to be achieved. Many wetlands are designed with specific goals in mind, so what works in one type of wetland may not achieve what is needed elsewhere.
Horizons' Freshwater and partnerships manager Logan Brown said that in Cambridge for example a 80-90 per cent reduction in nitrate was achieved by a wetland on farms there.
Horizons' contribution to this plan is 10 per cent of the total cost, which is not expected to have an impact on rates.
Former Horowhenua mayor Brendan Duffy, who has been asked to chair the Alliance, said the wetland project is 'visionary'.
"This is an iwi-led project. About a year ago Muaupoko Tribal Authority gathered a large group of interested parties around the table for a meeting as it was clear that the problem needed a multi-pronged approach which was too big for any one group to tackle," he said.
Nicky Brady and David Clapperton from Horowhenua District Council were involved from the start and saw the value of their approach. HDC came up with money for exploratory work and prepared a paper on a wetland for the Arawhata catchment. They also prepared a funding application with the Provincial Growth Fund.
"It soon became apparent that the Crown Infrastructure Partners funding was the best fit for this as it catered for works costing more than $10 million, was shuffle ready and could be implemented at pace and would provide jobs," Duffy said.
"This is our one opportunity to get this right," he said. "It will need stormwater remedial work and will be the biggest financial contribution ever to improve the water quality in the lake."
Implementation of the project will depend on landowners being prepared to sell.
The funding which was applied for in the end by Horizons allowed them to describe the plan in some detail. It will create the biggest wetland in the country which will have many benefits to the community, including recreational. There will be walkways, cycle paths, education booths, plant nurseries, training opportunities for landscape design and plant growing.
It is a project government agencies as well as minister David Parker are excited about.
As a group the Arawhata Wetland Alliance approached other agencies, such as MfE and Horizons to make this work and found people willing to listen.
The alliance includes representatives from Horowhenua Lake Trustees, Muaupoko Tribal Authority, Department of Conservation, Ministry of Primary Industries, Horowhenua District Council, Ministry of Business Innovation and Employment, Te Puni Kokiri, Horowhenua Vegetable Growers Association and NZ Institute of Economic Research.