The move triggered fears from the community the hospitals were facing permanent closure.
The suggestion, however, was ruled out by the Canterbury District Health Board (DHB) which gave assurances those uplifted would be back within six weeks of the Omicron outbreak's peak.
But with the Government cutting DHBs and establishing a national health service body, Powell said the delivery of healthcare in rural communities could be in jeopardy.
"The threat to rural health is decisions will be made much further away from where those localities and communities are," he said.
"[The Canterbury DHB] has defined responsibilities for the whole of its population and its care, from what happens in general practice, rest-homes, treatment in hospitals...that disappears from July 1.
"Those running the hospitals will no longer have a responsibility for the care outside of the hospitals."
Powell said rural hospitals in Canterbury were "potentially" endangered.
"The further away decision-makers are from understanding what smaller hospitals do, the less they know their importance.
"There's a greater risk of the wrong decisions being made because the nature of rural health may not fully be understood."
In North Canterbury, Friends of Oxford Hospital president Linda Huria said a permanent closure of Oxford Hospital would be "very devastating".
"It's a focal point of the community...the community would fight for it."
Oxford was one of the four temporarily closed by the DHB due to rapidly rising Covid-19 cases.
The Future of Health website said Health NZ's locality model would enable much greater community consultation, involvement, and representation on how health care was designed and delivered, an assertion echoed by Health Minister Andrew Little, as reported by the NZ Herald last week.
Powell rubbished the remarks and said it was nothing more than a rhetorical soundbite.
"They haven't worked it out...they have no idea."
The temporary closures of Oxford, Waikari, Darfield and Ellesmere hospitals were touched on by the health select committee during last week's Canterbury DHB annual review.
DHB chair Sir John Hansen told Waimakariri MP Matt Doocey long term decisions around the hospitals were out of the board's hands.
"I've made it very plain that it is not up to this board to make any longer term decisions around those rural hospitals given the reforms that are coming along," he said.
"It is a decision for Health NZ and others."