But the Kohupatiki Marae Trustees have declared in a letter to Hawke's Bay Regional Council chair Rex Graham that they do not support the WCO.
Written by chairman Wayne Ormsby, the letter says the "first and only time" the marae board of trustees had "ever" discussed the WCO was at a special meeting at their marae on October 30. The application was lodged in 2015.
The letter claims the application was made on behalf of Ngati Hori ki Kohupatiki by two trustees, who did not consult with the other eight.
"The outcome of [October's] special meeting was a motion moved, seconded, and carried stating 'The Kohupatiki Marae Trustees do not support the Water Conservation Order'," Mr Ormsby wrote.
Mr Ormsby could not be reached for comment yesterday. But marae trustee Api Robin said the two trustees may have had the right to make the application on behalf of Ngati Hori - one of the two hapu - but not Kohupatiki.
"Once they mentioned Kohupatiki ... that implicates all of us and so that's where we had to draw the line, that many of our whanau did not support the WCO and these two members had no right to use Kohupatiki."
When asked why the trustees declared this stance just ahead of the hearings, Mr Robin said many members only heard about the application several months ago through the media.
On what this could mean for the application, Mr Robin said the use of Kohupatiki could be a concern, but they would need to see what happened during the hearing.
The hearing schedule does not feature any presentations from Ngati Hori ki Kohupatiki, but he said some members might need to appear to speak on the issue.
What this means for the WCO is unclear.
The special tribunal, appointed by the Minister for the Environment, could not comment on the matter. The Environmental Protection Agency - which provides support for the hearing - was also unable to comment.
However a spokeswoman said "this is something that the special tribunal may address over the course of the hearing".
Mr Graham - who received the letter- said he thought this would have "a very big impact on the application because it is clear that Kohupatiki marae doesn't support the [WCO]".
Hawke's Bay Regional Council chief executive James Palmer said from their perspective, it was a matter for the applicants to address and clarify with the special tribunal.
"Upon receipt of the letter, our lawyer passed it on to the lawyer acting for the WCO applicants and asked them to clarify whether the letter has any implications for their application. We are currently awaiting their response."
Today the special tribunalwill begin hearing the application at Napier Conference Centre.
This will be the first stage of the hearing, to consider issues relating to the upper reaches of the Ngaruroro. It is expected to have finished between December 8 and 11.