Its completion became pressing following the devastating floods in Wolfenbüttel and Brunswick in the winter of 1946/47 when there were heavy falls of snow.

Before work started the small hamlet of Schulenberg in the valley had to be abandoned; it was rebuilt above the reservoir.

The large tour on the MS Aquamarin takes approximately 1.5 hours and can be started from all landing stages around the reservoir.

There is a circular route, using roads and paths, around the Oker Reservoir which is accessible to unmotorised vehicles or walkers.

Between the pre-dam and the primary dam there is a fully metalled circular path, which is used by cyclists, inline skaters and roller skiers.

Only the path between the pre-dam and Altenau, which is barred to motor vehicles, is not metalled, but is surfaced with gravel and stone.

In very calm conditions (no wind or precipitation and no man-made disturbances) a very flat surface forms on the reservoir which mirrors clearly the surrounding landscape.

The pre-dam (Vorsperre) of the Oker Reservoir is of the gravity dam type, with a height of 20.0 metres.

[1] The hydro-electric power station in Romkerhalle is fed via a pipe from the Oker Reservoir and has a capacity when completed of 4.14 MW.

It has a descent of 80 m, the nominal discharge is 6.5 m³ per second and it generates 12.5 million kWh per year.

The Grane Reservoir itself only has a relatively small catchment area and is reliant on other tributaries in order to be able to supply drinking water.

Like the Oker Reservoir, in calm weather conditions, it forms a very smooth water surface which reflects the surrounding countryside very clearly.