The Renaelva river flows into the Glomma in Åmot municipality in the county of Hedmark, Norway. One bridge that connect east and west side of the river, is Kjøllsæter Bridge. A sideriver to Renaelva is Julussa which is about 30 km long, coming from south, through the valley Julussdalen.
The Rena watershed has a drainage area of 3,967 km².
A tunnel has been built to transport part of the water from the upper Glåma river into the Rena river in order to optimize the production of electricity by power plants.