Tomahawk Lagoon

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Consultation has concluded

Tomahawk Lagoon is located at the southern end of Otago Peninsula and consists of two shallow brackish water lagoons. These are joined by a narrow channel and a weir structure, and share a common sea outlet.

The area is a wildlife refuge managed by the Department of Conservation and contains the threatened plant species Isolepis basilaris on the margin of the lagoon. It’s also a regionally significant wetland habitat for waterfowl and waders with a variety of bird species present. The area is part of a chain of feeding habitats along the coast used by migrating birds, and is an important habitat for native fish and eels. The area is important ecologically as it is defined as a marsh and less than 15% of original marshes remain in Otago.

Citizen Science water quality monitoring is undertaken by ECOtago monthly. Their results show that turbidity, E. coli, nitrates and phosphate levels are elevated within the lagoon, which is affecting water quality. Cyanobacteria, a toxic bacterium that can be harmful to humans and animals, is also regularly found within the lagoon in summer months.

Following a scoping exercise in 2017-18, the community agreed that the issues for the area are:

  • Algal booms
  • Water quality data
  • Swimmable water
  • Pest management (animals and weeds)
  • The weir
  • Flooding
  • Sedimentation

The goals that were identified were:

1. The natural environment of Tomahawk Lagoon and its ecosystem to be protected and enhanced

2. Appropriate recreational uses of Tomahawk Lagoon to be protected and enhanced

Priority projects

A number of projects were suggested by the community to achieve these goals. Some would involve ORC and others would involve DCC or community organisations. The majority of projects would rely on confirmed funding to enable them to go ahead.


Hear Libby Caldwell, Project Delivery Specialist, talking about Tomahawk Lagoon and how the community can have a say on which water quality projects should be prioritised on this podcast from Otago Access Radio here.

Tomahawk Lagoon is located at the southern end of Otago Peninsula and consists of two shallow brackish water lagoons. These are joined by a narrow channel and a weir structure, and share a common sea outlet.

The area is a wildlife refuge managed by the Department of Conservation and contains the threatened plant species Isolepis basilaris on the margin of the lagoon. It’s also a regionally significant wetland habitat for waterfowl and waders with a variety of bird species present. The area is part of a chain of feeding habitats along the coast used by migrating birds, and is an important habitat for native fish and eels. The area is important ecologically as it is defined as a marsh and less than 15% of original marshes remain in Otago.

Citizen Science water quality monitoring is undertaken by ECOtago monthly. Their results show that turbidity, E. coli, nitrates and phosphate levels are elevated within the lagoon, which is affecting water quality. Cyanobacteria, a toxic bacterium that can be harmful to humans and animals, is also regularly found within the lagoon in summer months.

Following a scoping exercise in 2017-18, the community agreed that the issues for the area are:

  • Algal booms
  • Water quality data
  • Swimmable water
  • Pest management (animals and weeds)
  • The weir
  • Flooding
  • Sedimentation

The goals that were identified were:

1. The natural environment of Tomahawk Lagoon and its ecosystem to be protected and enhanced

2. Appropriate recreational uses of Tomahawk Lagoon to be protected and enhanced

Priority projects

A number of projects were suggested by the community to achieve these goals. Some would involve ORC and others would involve DCC or community organisations. The majority of projects would rely on confirmed funding to enable them to go ahead.


Hear Libby Caldwell, Project Delivery Specialist, talking about Tomahawk Lagoon and how the community can have a say on which water quality projects should be prioritised on this podcast from Otago Access Radio here.

  • Please drop by and tell us at Grants Braes Football Clubrooms on Thursday 29th April anytime from 3pm until 7.30pm. Pop in, look at the options, have a chat with our team, and let us know which three projects are the most important to you.

    Or you can tell us online in the survey below:

    Consultation has concluded
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