The fire has spread through more than 1000 hectares of mānuka scrub and peat soils at Awarua.
Low temperatures and dew helped to contain the fire overnight, and Fire and Emergency has nine helicopters and nine ground crews on the fire ground today.
In an update this afternoon Fire and Emergency New Zealand said the fire is now 1350ha (the increase is due to updated mapping) with a perimeter of 26km.
Incident Controller Mark Mawhinney says he was pleased with the progress they have made.
"They have done an amazing job in some challenging conditions," he says.
Weather forecast predicts southwest winds 75-90kmh, possible gusts of 100kmh.
"These conditions increase the chance of the fire becoming more active, Waituna residents may see more smoke in the air tomorrow," Mr Mawhinney said.
"Please stay away from the area to keep yourself, and our firefighters, safe - it is still an active fire.
"Crews will be back on site tomorrow morning to continue extinguishing the fire."
Te Rūnaka o Awarua Kaiwhakahaere Dean Whaanga said the Waituna Wetland was used by generations of Awarua tīpuna as a giant food basket to feed whānau living at nearby settlements, and was home to many memories and traditions.
"I have strong memories of visiting this extraordinary place while growing up and feeling the mauri (life force) of the whenua and awa," he said.
"Our tīpuna had extensive knowledge of whakapapa, traditional trails and tauranga waka [canoe landing places], places for gathering kai and other taoka, as well as ways to use the resources of Waituna.
"Because this area was so important to our rūnaka, there are many urupā and wāhi tapu sites near Waituna where our tīpuna are buried. These are places holding the memories, traditions, victories and defeats of Kāi Tahu tīpuna."
Awarua tīpuna regularly harvested their cultural materials as well including paru or black mud for making dyes.
He said the rūnaka was thankful for the efforts of firefighters.
"We will have to wait until the fire is extinguished to fully understand what has been lost," Whaanga said.
"It's incredibly sad some of the taoka species found here will have likely died in the fire, but we're comforted knowing the landscape will heal over time.
"We will ensure we continue to pass down the kōrero of our tīpuna about this special place to future generations of our whānau."
Fire and Emergency said north-west winds of up to 15kmh were predicted for today which were ideal conditions for firefighters to continue to make the fire safe.
There was some rain forecast, but it was not expected to be enough to make a difference to the fire.
Fire and Emergency was urging people not to fly drones near the fire after one was spotted.
"This will result in helicopters having to be grounded, impacting firefighting efforts."
Environment Southland has raised concerns about the flora and fauna losses.
Its integrated catchment management general manager Paul Hulse, said the fire was in a wetland of international significance and the losses could potentially be devastating.
"As well as the close-knit Waituna community, the wider Southland community will be upset to see the fire burning in close proximity," Hulse said.
"While Southland remains in a drought situation, Fire and Emergency NZ has confirmed that the water being used to control the fire comes from tarns within the wetland, the Waituna Lagoon and the sea."
Waituna Wetland was formally recognised by a statutory acknowledgement in the Ngāi Tahu Claims Settlement Act 1998.
- additional reporting ODT
