ENVIRONMENT REMEDIATION
The sediment trap near the shores of Lake Horowhenua.
Restoring Horowhenua’s waters Words by: Jackie Harrigan
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substantial grant from the Covid Recovery Jobs for Nature fund has supersized plans to remediate the badly degraded water quality in Lake Horowhenua. The lake, to the west of Levin, has been degraded over many years by the effects of sediment, nitrogen and phosphorus leaching from nearby farms, both sheep and beef and dairy, by major horticulture operations and from the impact of stormwater and urban run-off. Lake Horowhenua is a taonga for local iwi/hapū and was once an important source of food for local iwi and a popular recreational playground. In 2013, the Lake Horowhenua Trust, Horizons Regional Council, Horowhenua District Council, the Lake Horowhenua Domain Board and Department of Conservation formed the Lake Horowhenua Accord, a collaborative effort to invest with the crown in a number of projects related to improving the health of the lake. The accord has implemented a range of projects including a Freshwater Clean-up fund work programme and a Te mana o
te wai work programme, both of which have contributed to a range of projects to enhance the lake. Building on the idea of a local alliance that involved local iwi, growers and community members, Horizons Regional Council has secured extra funding of $11.2 million through the Jobs for Nature fund, under the Ministry for the Environment, to build a wetland complex to reduce sediment and nutrient inputs into the lake.
Sheep and beef farms cover about 43% of the lake’s total 7000ha catchment while dairying makes up about 19%.
The project was first planned to cover about half of a dairy farm in the catchment, however the programme was rescoped to buy the entire farm, which was purchased in June 2021. This project, co-chaired by the Regional Council Chair Rachel Keedwell and Lake Trust Chair
Dairy Exporter | www.nzfarmlife.co.nz | December 2021
Clinton Hemana, has a governance team that includes iwi, the Lake Trust, district and regional council. The wetland complex development is one part of the plan to reduce both sediment and nutrients (nitrogen and phosphorus) flowing into the lake. Weed harvesting on the lake is another strand to the clean-up project, along with an investment of $4-5m from the Horowhenua District Council on stormwater upgrades. Lake weed alters the chemistry of the lake by increasing the pH of the water, lowering the nitrate concentration (raising the toxic ammonia concentration) and providing a favourable environment for phosphorus release and promoting cyanobacteria blooms. Harvesting weed interrupts this cycle and provides an environment more favourable to fish and other aquatic life, including native lake plants. Horizons chair Rachel Keedwell says the wetland complex and weed harvesting are two significant projects that partners are pleased to have underway. “Both are complementary to a number of other past and planned interventions that will help restore pride and mana to Lake Horowhenua and enhance its social, 65
