Ecotago Charitable Trust had been working to improve the water quality in the degraded lagoon since 2016, trust chairman Andrew Innes said.
It was pleasing the council had accelerated work in the area and it validated the trust’s own work, Mr Innes said.
"We are just so delighted," he said.
"Some of us like to think that us talking to them and nagging them has encouraged them to take a more positive interest in Tomahawk Lagoon than they had in the past."
After increasing angst over algal blooms in the lagoon several years ago, the group — made up of teachers, scientists, students and concerned community members — started their own water quality monitoring programme at the lagoon.
For the council to now commit to a catchment management plan showed the importance of that work, Mr Innes said.
"At the start of it, you feel like you’re crashing about in the undergrowth," Mr Innes said.
The ecologist the council employed for its forthcoming ecological assessment would use Ecotago data, which provided valuable information and a good starting point, she said.
The council’s implementation committee last week approved the initial management plan, its ongoing development and the project’s implementation.
In a statement, the council said engagement with the community identified an ecological assessment, permanent water quality monitoring and the formation of a catchment community group as top priorities.
The council budgeted $100,000 in its long-term plan towards improving biodiversity and water quality in Tomahawk Lagoon in the coming 2022-23 financial year, and a further $160,000 in the following two years.
At the same meeting the council also approved a management plan and a similar work programme for South Otago’s Lake Tuakitoto.
The council says Tomahawk Lagoon is a regionally significant habitat for numerous plant species, waterfowl and waders.
Lake Tuakitoto is habitat for nationally and internationally rare or threatened species, including the rare Australasian bittern and banded dotterel, and is a breeding ground for the uncommon marsh and spotless crake and the South Island fernbird, the council says.