The Friends of the Whanganui River will meet on Sunday to consider the group's future, treasurer Pauline Walton says.
The group was started in 1988 by historian and adventurer Arthur Bates. It was for "non-political fans" of the Whanganui River, and aimed to publicise the river's history and encourage its use.
Since then the Friends have published yearly annuals and led visits to places on the river and its many tributaries. They also put on two trips for the public, in the Whanganui Summer Programme.
There were about 400 members in the group's heyday. Many no longer live in the area.
"A good many are older people. A good many had family connections, particularly in the Mangapurua Valley," Mrs Walton said.