Two bike riders discovered the severely decomposed remains in half a metre of water at a property about 20 kilometres south of Murwillumbah last week, while using a popular track that runs past the property.
A post-mortem examination on Monday identified the body and prompted the homicide investigation, which will be run under Strike Force Milera. Detectives from the State Crime Command's homicide squad and other specialised units will be deployed to the Northern Rivers.
Whear's three children, in a statement released on behalf of the family, said they were "devastated and horrified" by the development and are demanding answers for the "callous, inhumane act".
"We are left facing a future without her, carrying unimaginable grief and unanswered questions," the family said.
Whear, who was last seen on February 19, was captured on CCTV at a Murwillumbah service station the day she disappeared.