The Waitaki council voted unanimously last week to join the Gore, Central Otago, and Clutha councils to share resources and develop water.
Its own standalone project was rejected by the Department of Internal Affairs.
Gore Mayor Ben Bell said it was a "fantastic result" to have WDC back in the fold.
"It’s been made a lot easier because we’ve done a lot of modelling work with them, so bringing them back was easy," he said.
Mr Bell was less enthusiastic about the decision by Timaru and Mackenzie councils to not join the shared waters CCO, but said the door might be open for future co-operation.
"Obviously [it’s] a bit sad and disappointing by Timaru and Mackenzie deciding not to come with us but I understand they have to make the decision that’s for their community. Now we’ll slowly box on with the four and set up this water scheme.
"The door is probably temporarily closed while we set up, but there will be other CCOs and other councils, once we’re set up and fully formed, I’m sure we’ll be pretty welcoming of other councils should they need to join another CCO," he said.
For Mr Bell, although the departure was a bit of a shock, he understood the reasoning and said he has no worries about the stability of the partnership.
Waitaki District Mayor Mel Tavendale said despite "good conversations that were had in good faith" it was a lost opportunity.
"I do think it’s a missed opportunity for real cost savings, but I recognise that everyone has their drivers and their concerns that they’re addressing through this conversation."
Mrs Tavendale said looking across all councils helped them to better understand the costs involved.
"But ring-fencing is the only effect that it has on us and it would have been an effect either way, whether we looked north or south.
"We’re still working on our asset assessment and what that looks like."
Mrs Tavendale said they had engaged with all six councils over the last two months.
"From the discussions we’ve had there are clear benefits of a larger organisation in both efficiency and cost savings — choosing a larger entity will deliver the best outcome for Waitaki."
Most important was affordability for the community.
All councils wanted a sustainable and reliable network, Mrs Tavendale said.
And there was "a lot less risk" staying with the South, she said.
Mrs Tavendale said the Southern Waters group had "a really open door" for Waitaki throughout the conversation and the understanding of "rural water" was a big plus in those discussions.
In a joint statement, Central Otago District Mayor Tamah Alley, Clutha District Mayor Jock Martin and Gore District Mayor Ben Bell said the inclusion of Waitaki in the Southern Waters group would strengthen the water services entity.
Mr Martin said Southern Waters had always been open to working with like-minded councils to deliver positive outcomes for their communities.
"This isn’t about leveraging for advantage.
"It’s about building a model that is financially sustainable, protects public health and the environment, and gives our communities confidence in how their water services are delivered," he said. — additional reporting Juliana Chin
