It is not far from Bad Harzburg or Torfhaus to the Oker reservoir. In the Lower Saxon district of Goslar, the Oker flows into a reservoir that is bordered by the dam.
We reach the reservoir via the B498, which runs parallel to the Oker between Altenau and Goslar. It runs along the reservoir and crosses it over the Weißwasser bridge. From there it is not far to the Oker reservoir. There is a small car park at the side of the road, from where it is only a few steps to the imposing dam wall.
The Oker reservoir is 260 metres long. You can walk along it and enjoy the view of the reservoir on one side and the view of the valley with the small river Oker on the other. If you want to look into the valley, you should not be afraid of heights. The dam wall is 75 metres high and the valley is correspondingly deep at the dam wall’s feet. But the view is worth it, it is quite imposing how the Oker dam rises.
As I walk along the wall, I imagine the masses of water pressing against the concrete and admire once again the work of structural engineers and civil engineers who have calculated this.
Construction of the Oker Dam
The Harzwasserwerke began building the dam as early as 1938-42. First, they laid the roads in the valley and built the bridges over the valley that still exist today. During the Second World War, construction work was initially interrupted. The construction of the dam took place after the war from 1952-56.
The forest workers’ settlement Unterschulenberg in the valley had to be abandoned. It was rebuilt at a different location. At times when the reservoir stores little water, the remains of some houses and the old valley road can be discovered in the lake. The legend that the church spire then looks out of the water and the bells ring should not be believed, however.
The dam is a so-called arch-weight wall. Originally, a different construction was planned, but the contractors were able to prove that with their construction method less concrete would be needed and the wall would still serve its purpose. And so far they seem to have been right.
I read that there is the possibility to visit the inside of this impressive dust structure. Unfortunately, I didn’t discover any dates for such a tour at the time we were there. I would have been really interested in that.
Tourism at and on the Okertal Reservoir
You can cruise around the reservoir on a scheduled boat service from March to December. A complete round trip with the “MS AquaMarin” takes about 90 minutes.
It is also possible to go out on the water with non-motorised boats. There is the possibility to rent pedal boats, for example.
Swimming and diving in the reservoir is allowed in some areas. However, dives must be announced. Those who would like to dive into the remains of the old settlement must be well equipped. It is about 20 metres deep and it can be very dark.
Paths lead around the reservoir so that it can be completely circumnavigated on foot or by bicycle.
There are several restaurants on the shore of the lake and there is a camping site.
Here are a few more facts about the reservoir and the dam
Length of the dam wall: 260 metres
Height of the dam wall: 70 metres
Width of the crown of the dam: 8 metres
Width of the base of the dam: 19 metres
Concrete volume of the wall: 140.00 m³
The reservoir is divided into two main arms, the Altenau and the Schulenberg arms. These are separated from each other by a mountain range. There is storage space for 46.85 million cubic metres of water in the Okterstausee. The total water surface area is 2.25 square kilometres. This is slightly larger than the entire Großer Tiergarten in Berlin or comparable to more than 310 football fields.
The lake has a maximum depth of 65 metres.
The water of the reservoir is collected over an area of 85 km². About 40% of the water comes from the river Oker. The Oker flows through the lake in a south-north direction.
Other rivers also supply water to the lake. These include: Schwarzes Wasser, Kellwasser, Kalbe, Große Hune, Lange, Schalke, Riesenbach, Aeke and Große Bramke.
The water drives the turbines in the Romkerhalle hydropower plant of the Harzwasserwerke. It is used to generate electricity. When the water level is low, the reservoir feeds the river and when the water level is high, it regulates the water level to prevent flooding.