Lake Horowhenua

The lake catchment area is nearly 65 per cent pasture, which is a source of lake eutrophication (nutrient enrichment) that can lead to increased plant growth and/or algal blooms. The lake is located within a target catchment for nutrient management under Horizons Regional Council’s One Plan. Kākahi (native freshwater mussels), an important indicator of water quality, were observed by NIWA during a survey in 2017.

Nutrients from 25 years of treated sewerage discharge into the lake and ongoing land-use effects has led to the present hypertrophic condition (lakes that have been excessively enriched with nutrients). The lake has cyanobacterial blooms and a problem with dense weed growth that can interfere with contact recreation during summer. Efforts to clean-up the lake have been ongoing for several decades and include the establishment of a full native planting buffer strip around the lake, and a formal catchment management strategy being established by Horizons Regional Council.

Alongside the science and restoration efforts, several key partners have developed and signed the Lake Horowhenua Accord. Five parties representing the Muaūpoko owners, community interests and statutory bodies have agreed to work together to provide leadership to halt the degradation and put in place remedial measures that will begin to return Lake Horowhenua to a taonga (treasure) that holds pride of place in the Horowhenua community. The Lake Horowhenua Clean-up Fund was established in 2014. Primary projects in this work programme are to provide physical and infrastructural assets to address the key issues of toxic algal blooms including through lake weed harvesting, sediment and nutrient inputs to the lake from rural and urban sources, and to improve habitat and access to the lake for native fish.