Because the river Grane itself does not deliver enough water for the 3 km long reservoir, a 7.4 km long diversion channel was built from the Oker river below the Oker Dam.

A further 4.8 km long diversion runs from the Radau to the Großer Romke and thus into the Oker-Grane Tunnel as well.

The operator of the Grane Dam, as well as its associated diversion systems and waterworks is the Harzwasserwerke.

The water from the reservoir is pumped up into a compensating storage basin of 60,000 m³ capacity, from where it flows to the waterworks.

A track for maintenance was laid around the reservoir, which is also open to walkers and cyclists and is about 17 km long.