Ngati Hori ki Kohupatiki said it was backing the application because of the Ngaururo's cultural importance to Hawke's Bay Maori.
"This application recognises the Ngaruroro's significance to Ngati Hori, and Ngati Kahungunu generally, and strengthens our hapu's efforts to restore the mana and mauri of these waterways," said Margaret McGuire, Chairwoman of Ngati Hori ki Kohupatiki.
The other applicants are already working closely with Ngati Kahungunu in the iwi's kaitiaki role.
Mr Johnson said anglers treasure the upper Ngaruroro catchment because of its outstanding backcountry rainbow trout fishery, spectacular scenery and some of the clearest water in the country.
"The application our group has made to the Minister today is backed by a substantial volume of evidence which makes a very strong case for a Water Conservation Order on the Ngaruroro and Clive," he said.
"We are confident this large body of evidence will result in the Minister accepting our application and initiating the inquiry process."
Once the Minister accepts an application for a WCO, which offers similar protection to that of a National Park, a special tribunal will be set up to examine the case for a WCO and invite submissions from the public and special interest groups.
The tribunal will then hold a hearing and the Ngaruroro applicants are optimistic it will make a decision within a year.