Lake’s wetland plans get clearer
A large project to improve the state of one of New Zealand’s most polluted lakes is making progress, with detailed designs showing the extent of work to come.
Horizons Regional Council is working with various groups to build a wetland near Lake Horowhenua.
The lake used to be a source of kai, but is now notoriously polluted due to a combination of residential and rural waste and runoff.
The wetland, which will be built on land currently used for dairy farming to the south of the lake, would process water, much of it flowing from vegetable farms, before it enters the lake.
The water contains lots of sediment, nitrate and phosphorus, contributing to the growth of weed and algae in the lake.
The land was purchased for $6.7 million, with Horizons paying $1m and the rest coming from Government coffers.
Horizons recently released draft plans for the wetland, which would be built in three stages.
The first stage included installing pipes and drains, planting, deepening some existing drains and work around the existing sediment trap.
The next stages would be further upgrades to enlarge the wetland’s capacity.
Horizons freshwater manager Logan Brown said the design came about after a long list of wetland types was whittled down.
The draft design included a mixture of less natural and more natural concepts.
The area was perfect for a wetland, with some people able to remember far back enough to a time when one existed in the area, Brown said.
Modelling showed the wetland would remove up to 70% of nitrate in the water, as well as sediment and phosphorus.
Brown said the wetland was not the only part of the process of restoring Lake Horowhenua.
Some actions are already under way, such as the harvesting of weed from the lake bed.
But other measures, such as limiting the amount of nitrate getting into waterways, were also part of the plan.
Public consultation had been very useful so far, giving Horizons things to consider and provide more information about, he said.
The design team was aware the water table in the area could be impacted by the wetland, so the plans included interventions to ensure that neighbouring landowners were not impacted.
The first stage of the wetland needed to be built by 2025.
Brown said the timeframe was tight, given consenting still needed to go ahead, but doable.
Horizons chairperson Rachel Keedwell said the wetland would not just be ‘‘the ambulance at the bottom of the cliff’’, with new freshwater regulations and onfarm projects also playing a part.
The wetland would also have a recreational aspect in the future, making it a community asset for the future, she said.
People can view the plans on Horizons’ website, while a community meeting is taking place at Manakau Hall on Sunday from 10am until noon.
Feedback can be provided by calling 0508 800 800 or emailing horowhenua.wetlandcomplex@ horizons.govt.nz or calling 0508 800 800.