The role is a single one, to be filled by two people. Rather than one appointed by the Crown and the other by Whanganui iwi, both will be chosen jointly by Crown and iwi.
Ms Main said names were put forward to Whanganui iwi, and a series of meetings held.
On the Crown side, she said recommendations were made to Treaty Negotiations Minister Chris Finlayson, and people were asked whether they were interested.
There were other aspects of the process that she couldn't talk about.
However, she was looking forward to the appointment of the advisory group and its work to promote the river's wellbeing.
The two people chosen to be pou (poles, supports) would need time to accept and understand their role, she said. The two will speak on behalf of the river, uphold its legal status and values and promote its health and wellbeing.
The deed of settlement says they will also carry out "landowner" functions and administer Te Korotete o Te Awa Tupua, the $30 million contestible fund to support the river's health.
The appointments last for three years.
The pou will get administrative support from Nga Tangata Tiaki, the river's new governance entity, and advice from Te Karewao, a group of 17 iwi and local authority people.