Nick Ward and Peter Scott won the seats ahead of Toni Serverin.
The South Canterbury/Ōtuhituhi regional constituency includes the northern part of the Waitaki district, near the Waitaki River.
Mr Ward, who had served one term, won 12,300 votes while Mr Scott tallied 8403.
Formerly the chairman of Environment Canterbury, Mr Scott resigned in September last year following revelations his council-provided car exceeded the speed limit 678 times since January last year, with a top speed of 157kmh.
He was also investigated last year after he said in a radio interview he was probably "operating illegally" on his South Canterbury farm.
He would be entering his fourth term.
The mayoral race in Waimate was close, with progress results giving incumbent Craig Rowley a lead of fewer than 80 votes.
The progress results had Mr Rowley on 912 votes, with his nearest rival Sharyn Cain sitting on 836 votes.
Mrs Cain had been deputy mayor and had not sought a council seat this election
One-term councillor Rick Stevens was sitting on 655 votes, in third.
In Mackenzie, Scott Aronsen is the clear leader in a five-strong field for the mayoralty with 85% of the vote counted.
He received 926 votes with acting-mayor Karen Morgan the next best on 337.
Anne Munro was voted in as mayor in 2022 but she stood aside more than a year ago after being diagnosed with cancer.
She announced in July she was not running for mayor.
