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Tomohaka / Tomahawk Lagoon
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Tomahawk Lagoon is located at the southern end of the Otago Peninsula. It consists of two shallow brackish water lagoons which are joined by a narrow channel and weir/gate structure and share a common sea outlet.
Tomahawk Lagoon is a wildlife refuge of 33 hectares that is managed by the Department of Conservation which contains the threatened plant species Isolepis basilaris on the margin of the lagoon. The area is important ecologically as it is defined as a marsh and less than 15% of original marshes remain in Otago.
The lagoon is a regionally significant wetland habitat for waterfowl and waders with a variety of bird species present and is part of a chain of feeding habitats along the coast used by migrating birds. Tomahawk Lagoon is also important habitat for native fish and eels.
Citizen Science results indicate that turbidity, E. coli, nitrates and phosphate levels are all exceeding national guidelines. Cyanobacteria is also regularly found within the lagoon over the summer months which is a toxic bacterium which can be harmful to humans and animals.
Associate Professor Marc Schallenberg examines a sediment core sample from Tomahawk Lagoon
a-pied-stilt-or-white-headed-stilt-himantopus-leucocephalus-is-bending-over-and-looking-between-its-long-legs-at-tomahawk-lagoon-in-dunedin-new-zealand
a-pied-stilt-or-white-headed-stilt-himantopus-leucocephalus-is-moving-in-the-strong-wind-at-tomahawk-lagoon
a-marsh-crake-or-baillons-crake-porzana-pusilla-new-zealand-endemic-subspecies-p-p-affinis-is-walking-foraging-in-the-reeds-near-water-at-tomahawk-lagoon
In 2017, in response to concerns about water quality, our staff began to work with the local community to scope lake restoration works for Tomahawk Lagoon.
ORC dedicated $260,000 over three years (2022-2025) to enhance the Tomahawk Lagoon Catchment through community action to contribute to a healthy ecosystem for all to enjoy.
In 2018, two workshops were held with the community which identified community goals and values for the Tomahawk Lagoon catchment, and it identified potential projects for the catchment.
In 2021, a consultation process was undertaken with the community, mana whenua, and key stakeholders to vote on the highest priority actions to be implemented for the catchment.
Three priority actions, along with the collective vision and values for Tomahawk Lagoon, were compiled in the Tomahawk Lagoon Outline Management Plan.
Catchment group formed and supported
This work is being led by the community and Otago Catchment Community. ORC continues to support community members in the formation of a ‘Tomahawk Lagoon Catchment Group’.
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tomahawk-lagoon-photo-christopher-peacocke
Ecological Assessment
ORC contracted Cawthron Institute to undertake an Ecological Assessment of Tomahawk Lagoon. ORC contracted Cawthron Institute to undertake an Ecological Assessment of Tomahawk Lagoon.
The aim of the ecological assessment was to identify drivers for the current ecological status of the lake and to identify possible actions that the ORC, in collaboration with the community, mana whenua, and key stakeholders, could undertake to make the catchment more resilient. The ecological assessment consisted of an analysis of historical data, and a fieldwork component. The final report on the ecological assessment was submitted to ORC on 31 July 2023, which was then shared to mana whenua, community representatives, and key stakeholders.
Recommended management actions focussed on reducing contaminants in the lagoons. These included:
- Exploring the possibility of zoning the catchment as a nutrient-sensitive zone in the Otago Regional Council Land / Water Plan
- Undertaking fencing and riparian planting; buffers in forestry areas
- Enhancing existing wetlands in the catchment
Water Quality Data
ORC has established a monitoring site as part of our State of the Environment programme (August 2022) in the deepest point of the upper lagoon. The site name is Tomahawk Lagoon at Tomahawk Mid, and we perform monthly sampling for various water quality parameters (e.g., nutrients, chlorophyl-a, bacteria levels, and water clarity) and physico-chemical parameters (water temperature, pH, dissolved oxygen, conductivity, etc).
Stormwater education - April 2024
A stormwater education event was held at Domain Hall in April 2024.
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Tomahawk Lagoon Community Day — April 2024
Open day - July 2023
Open day held at Tomahawk Lagoon.
ORC has developed an Implementation Plan with the community.
The Vision is a thriving Tomahawk Lagoon catchment, where water quality and biodiversity are maintained and enhanced through community action to contribute to a healthy ecosystem for all to enjoy.
ORC has more funding available to help landowners enhance habitat on their properties, particularly wetlands and alongside creeks.
More stormwater education and signage is being developed.
If you would like to get involved with the local community on this project, follow them on social media:
If you would like to know more about this project or have any other questions about the work at Tomahawk Lagoon, you can contact our customer services team:
Phone: 0800 474 082
Email: customerservices@orc.govt.nz
