Robson Lagoon, about 7km northeast of Balclutha, is a key part of the Lake Tuakitoto Wetland complex.
The lagoon, lake and wetlands is described as a rush and sedge swamp, lowland lake, that has an artificial water level.
Otago Regional Council engineering manager Michelle Mifflin said the flow gate project was within the ORC’s catchment of the Lower Clutha Flood Protection and Drainage Scheme.
It aimed to change the flow management system around the wetland to encourage the normal flows of its tributaries (Lovells Stream and Stoney Creek) which enter Robson Lagoon, while managing drainage in the area, Ms Mifflin said.
The project was co-funded by the ORC and the Ministry of Business, Innovation and Employment.
It upgraded ageing infrastructure and assisted with water management around the 566ha lagoon complex, she said.
The solar powered flow gate would be opened when there were higher flows from the tributaries, diverting water past the lagoon through a drain into the lake.
In lower flows, the gate would close and the tributaries could flow into and replenish the lagoon.
"This project will go a long way to providing certainty in maintaining minimum water levels for the wetland, and also provide adequate land drainage."
Better control of water flows would also enhance protection of the area’s natural and ecological values, which are number five on New Zealand’s top 10 list of wetland wildlife habitats.
There was a highly diverse "mosaic" of vegetation types and wildlife habitats in the area, hosting nationally or internationally rare or threatened species.
The area provided roosting, feeding and breeding habitat for the threatened Australasian bittern and banded dotterel.
It was a breeding area for the uncommon marsh crake, spotless crake and South Island fernbird.
It supported a significant proportion of the national population of mallard and Australasian shoveler (kuruwhengi), grey teal and black swan.
"It’s also considered nationally important as a freshwater fishery habitat.
"The new flow management structures will allow for sustainable habitat water levels and flows, and also provide for the safe passage of native fish with a small tunnel for them," Ms Mifflin said.
The area supported long and shortfin eels, whitebait, the common bully, giant galaxiid, freshwater mussels, perch and brown trout.
It also hosts threatened plant species such as swamp nettle and Isolepis basilaris.
The flow gate will be official opened on Wednesday.
