Most rivers are each inhabited by a powerful spirit which rules the waterway from headwaters to mouth. River dwellers worship him or her. Those spirits which inhabit tributary rivers, streams, and creeks are usually the children of the main river deities.
The three greatest rivers of Glorantha are all in Genertela. They are the Janube in Fronela, the Oslir in Peloria, and the Tanier in Ralios and Arolanit.