In an email to regional councillors, Transparent Hawke's Bay chairwoman Megan Rose said the aim of the meeting was to "provide the public with an overview of all sides of the discussion and to better enable those that need to make important decisions regarding the dam to do so".
Regional council chairman Fenton Wilson has declined the invitation because he will be in Wairoa on Thursday.
However the council's chief executive, Liz Lambert, and its resource management group manager, Iain Maxwell, have said they will attend.
Also attending will be Central Hawke's Bay farmer Hugh Ritchie, an existing irrigation user, Fish & Game environmental manager Corina Jordan, who has been instrumental in legal action related to the project, consultant Peter Fraser, a critic of the economics of the dam, and Jonathan Dick, Ngati Kahungunu's environment and natural resources director.
"We have received a huge amount of support for the meeting," Ms Rose said.