"The OIA request had resulted in the release of a map that outlined the addition of an extra irrigation zone [Zone N] to the scheme area. [Mrs] Hewitt's property sits inside this new area," Greenpeace's agriculture campaigner Gen Toop said.
Mrs Hewitt said she had also requested an exception from the Auditor-General so she could continue to participate in discussions and vote on significant decisions that were related to the dam.
"Any pecuniary interest I might have is uncertain and in any event no different to that of the general public," Mrs Hewitt said.
"[Or] it is so remote and insignificant that it cannot reasonably be regarded as likely to influence me in voting on or taking part in discussions relating to the [dam]?"
She said she has yet to receive a response from the Auditor-General.
"It is with regret that I must decline to participate in any discussions or decisions regarding the RWSS until such time as I receive a decision from the Auditor-General confirming it is appropriate for me to participate in such discussions or decisions."
A spokesman for the Office of the Auditor-General confirmed they had received an application from Cr Hewitt under the Local Authorities (Members' Interests) Act to take part in decisions about the dam.
"We are aware of the issues regarding [Mrs] Hewitt's potential conflicts of interest," he said.
"We are working through these issues with the council and Cr Hewitt, and we are currently waiting for some further information to support her application."
He said it was not appropriate for the office to comment any further.
The council's chief executive Liz Lambert, who sought the legal opinion to which Mrs Hewitt responded, said the issue was being addressed.
Cr Hewitt wanted to emphasise that this was a temporary decision.
"I am still endeavouring to represent the community to the absolute best of my ability," she said.
"I am following a prudent course of action - and I eagerly await a final determination [from the Auditor-General]."
Forest & Bird, who have also lodged a complaint, said it was difficult to tell when the dam company decided to add an additional Zone N to the irrigation scheme.
"The documents we have seen show that Cr Hewitt should have known from at least October last year that this zone would include her property and that as a result she would stand to gain from decisions by the council to invest public money in the scheme," the group's environmental lawyer Sally Gepp said.
"She should have declared her interest and stood aside from decision-making from that time."
Forest & Bird have also urged the Auditor-General not to grant Mrs Hewitt an exemption, saying the benefits of allowing her to participate in decisions relating to the scheme do not outweigh the risk that her participation will be regarded as distorting or tainting such decisions.
Ms Toop said it was "plain wrong" that Cr Hewitt hadn't declared a conflict of interest until now.
"It's uncanny timing that the council has only acknowledged this conflict of interest after people started making noise about it," she said.
Ms Toop said any decisions that had been made between when the new map was created in November 2015 and now must be reviewed in light of Cr Hewitt's admission.
"[Mrs] Hewitt has been part of critical decision-making about the future of Ruataniwha - decisions that could lead to her gaining financially," she said.
Ms Toop says Greenpeace is calling on the Ruataniwha process to be halted until such time as an external review about the conflict of interest has been completed.
