Lake Ōmāpere is known as the pātaka kai(food basket) of Ngapuhi(tribe), and taonga tuku iho(legacy resource) where the health of the lake and the health of the people are intertwined. Despite this, water quality has been devastated over the last century secondary to land-use activities. Statutory obligations by regulatory authorities to maintain water quality and surrounding ecosystems remain ineffectual. As one of only two lakes in New Zealand where the waterbody is owned by Māori, there is a unique opportunity to understand what Māori-led restoration of the lake can look like.
With a surface area of 1,261 hectares, the lake sits within a 3,154 hectare catchment of mixed land-use including beef cattle, dairy and crops. It previously supported New Zealand’s colonial settlement - with a burgeoning trade of timber, flax/fibre, fisheries. Lake Omapere supported the municipal water supply of Kaikohe between 1970-1984 until it experienced its first major algal bloom. Children swimming in the Utakura river downstream, developed sore eyes and diarrhea, consumers reported stomach upsets. Fish and mussels in the Hokianga harbour were said to turn bad not long after being gathered, and stock would not drink water from the lake or downstream (Lake Ōmāpere Taskforce report, 1986). Whilst the lake has continued to have algal blooms until the present day, the lake has experienced many short-term and single mechanistic interventions with no to minimal success, and most initiatives lacking sustainable, enduring partnerships (Lake Ōmāpere Trustees, 2023).
Lake Ōmāpere Trust wishes to restore the mauri(life-force) of Lake Ōmāpere, to support community wellbeing as it once did over a century ago. Earlier sediment sampling in Omapere has shown that total nitrogen and phosphorus are 40 and 20 times greater than that in the water column, respectively. Further modelling demonstrated that in-lake(sediment) phosphorus loading was 63% higher than catchment contribution (Verberg et al., 2012). Restoration of water quality requires both in-lake, and catchment level interventions (Hamilton, 2024) including the removal of high-nutrient sediment; edge of field interventions (riparian buffers; wetland restoration; sediment traps) and in-lake filtering involving natural mechanisms such as kākahi (freshwater mussel) and native macrophyte restoration (NIWA, 2024). Multiple examples of these latter methodologies can be found both in New Zealand, and internationally. Less utilised in New Zealand, the opportunity to utilise sediment removal as a critical restoration step, will broaden the New Zealand evidence base for this type of restoration methodology to be utilised to restore New Zealand lakes.