Grønfjellåga () is a river in Rana Municipality in Nordland county, Norway. The long river's source is the lakes Kallvatnet and Kopparvatnet. It then flows through the Grønfjelldalen valley while absorbing several smaller rivers, before it flows out as a tributary to the river Ranelva at the Dunderforsen waterfall (also called Stupforsen).
Media gallery These photos are from a place east of Stupforsen:
References