Warnings and Alerts

Active warnings and alerts for Lakes

• Lake Benmore weed control notice

  18 FEB 2026

  Toitū Te Whenua LINZ is undertaking lakeweed control work on Lake Benmore to target Lagarosiphon major. The herbicide diquat is used to control weed. As per the label recommendation, the public are advised to stay out of the treatment areas and refrain from taking water from the lake for any pu...
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  Lake Forsyth/Te Roto o Wairewa cyanobacteria health warning

  11 FEB 2026 By ENVIRONMENT CANTERBURY (KD)

  11 February 2026:  Health Warning – Harmful Algal Bloom in Te Roto o Wairewa Lake Forsyth Health New Zealand | Te Whatu Ora has issued a health warning after potentially toxic harmful blue-green algae (planktonic cyanobacteria) surface scum has been observed&...
• Lake Hood - Public health warning for potentially toxic algae (cyanobacteria)

  14 JAN 2026 By ENVIRONMENT CANTERBURY (KD)

  Health Warning – Harmful Algal Bloom in Lake Hood  Health New Zealand | Te Whatu Ora has issued a health warning after potentially toxic harmful blue-green algae (planktonic cyanobacteria) were found in Lake Hood.   People should avoid the Lake and animals, pa...
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  Lake Pegasus cyanobacteria warning

  10 DEC 2025 By ENVIRONMENT CANTERBURY (SK)

  Issued 10 December 2025: Health Warning – Algal Bloom in Lake Pegasus The National Public Health Service has issued a health warning after potentially toxic harmful blue-green algae (planktonic cyanobacteria) was found in Lake Pegasus   People should avoid the Lake and animals, particu...
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  Te Waihora/Lake Ellesmere cyanobacteria warning

  5 MAR 2024 By ENVIRONMENT CANTERBURY (GR)

  Update March 2024: Due to the high biomass of cyanobacteria in the lake the health warning is still current. 8 February 2022 to date Canterbury DHB’s Community and Public Health unit has issued a health warning after potentially toxic blue-green algae (planktonic cyanobacteria) was found in Te Waiho...
• Lake Rotorua - permanent cyanobacteria health warning

  6 MAR 2023

  Long term water testing indicates that there is a regular bloom of the potentially toxic cyanobacteria Anabaena and/or Microcystis present. There is a permanent health warning advising people to avoid contact with water at this lake. Environment Canterbury continues to monitor the lake on a regular...
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  St Annes Lagoon/Mata Kopae cyanobacteria warning

  7 JUL 2022 By ENVIRONMENT CANTERBURY

  Permanent Health Warning for Algal Bloom at Mata Kopae/St Anne’s Lagoon. Issued: 7 July 2022 Long term water testing indicates that potentially toxic cyanobacteria bloom periodically in Mata Kopae/St Anne’s Lagoon. There is a permanent health warning advising people (and animals) to avoid contact wi...