Oker Dam
The Okertalsperre is a dam in the Harz ( Lower Saxony). It is fed by the River Oker.
- 5.1 Vorsperre
- 5.2 hydropower plant Romkerhalle
- 5.3 Oker - Grane studs
- 5.4 equalization basin of the Okertalsperre
- 5.5 sewer
Technology
The dam in sheet form ( arch-gravity dam ) is 75 meters high, 260 meters long, can accumulate up to 47 million cubic meters of water and is used for power generation, low-water elevation and flood protection. Indirectly, it is also used for drinking water. The mean annual discharge is 75 million cubic meters. From Okertalsperre the hydroelectric plant Romkerhalle is fed.
In deciding to build an arch-gravity dam, it was a special proposal of exporting Contractors Dykerhoff & Widmann AG, Hochtief AG and Philipp Holzmann AG. They were able to demonstrate that in this construction significantly concrete could be saved.
The dam must only compressive forces and therefore can do entirely without reinforcement. To minimize the evolution of heat during setting of the concrete, a Grobrüttelbeton was used. For this purpose, up to 40 cm were vibrated large diabase stones in relatively normal concrete. Thus, the proportion of cement decreased in the concrete. Since the Diabassteine had a density of almost 3.0 tonnes per cubic meter, increased their proportion and the weight of the concrete, which the wall was added stability.
Overflows the dam
Table with technical data on the Okertalsperre
History and location
The construction of the Okertalsperre was started in the years 1938 to 1942 and then completed from 1952 to 1956. Urgently the continued construction was also after the snowy winter of 1946/47, devastating floods, especially in Wolfenbüttel and Braunschweig had occurred. Prior to the establishment of the small Talortschaft Schulenberg had to be abandoned; it was rebuilt above the lake. In low rainfall years can drop so much the level of the dam that residues of individual houses and the old valley road are visible with its bridges.
The Okertalsperre is located on the main road 498, which follows the course of the Oker between Goslar and Altenau. On the east bank runs along a forest road that is closed to public motor vehicle traffic.
With its many tributaries resembles the Okertalsperre the much larger Biggetalsperre in the Sauerland. For the same reason it is also called " Lucerne the resin ".
Photos from the construction
Main dam under construction
Main dam under construction
Viaduct as in 1954/55
Tourism
On the Okertalsperre each one liner for tourists runs from early March to early January ( in the off-season weekends only). This ship of the line connection is the maximum Points (above mean sea level ) in Lower Saxony. In addition, the Okerstausee is traveled during the summer months of numerous private, non-motorized water vehicles. The swimming and diving is outside cordoned-off areas, for example in the area of the dam also permitted. In winter Eisbadeveranstaltungen take place at sufficiently stable ice thickness. The Okerstausee can walk and non-motorized vehicles on roads and trails are surrounded completely. Between Vorstaumauer and main dam, there is a completely paved trail that is used by cyclists, inline skaters and Skirollerfahrern. Only the closed to motor vehicles way between Vorstaumauer and Altenau unpaved (gravel and stone path ). On the main road there is 498 in the summer months on weekends heavy motorcycle traffic (northern Directions to peat house ). Here lie along the dam several restaurants. In undisturbed water surface ( no wind, no rain, no human-induced disturbances ) is formed from the reservoir to a very smooth surface on which the surrounding landscape clearly reflected.
Okerstausee at low water
Oker in Okerstausee at low water
Branch of the Okerstausees at low water
Temporarily flooded bridge in Okerstausee at low water
Fish fauna
The Okertalsperre is predominantly a salmonid with brook trout, grayling, brook, rainbow and brown trout. In addition, pike, walleye, large perch, eel, burbot, carp, tench and numerous white fish occur. For the sport of fishing, visitor passes are issued.
To Okertalsperre associated facilities
Vorsperre
The pre-dam of Okertalsperre is equipped with a gravity dam, which has a height of 20.0 m. The pre-dam may build up to 520,000 cubic meters of water and is mainly used for water level regulation and keeping the Okertalsperre. The duration of storage (up to 15 m water depth at the Vorstaumauer ) was used to create a wetland in Kellwassertal. Only at very high water level in the dam and Okerstausee are pre-dam on the same water level. Then the water level can rise by up to 1.60 m in the pre-dam.
Vorsperre, Okerstauseeseite at low water
Hydropower plant Romkerhalle
The fed via a pipeline from the Okertalsperre hydropower plant in Romkerhalle has an installed power of 4.14 MW. It was made in 1956, and is equipped with a single Francis turbine. The slope is 80 m, the nominal flow 6.5 m³ per second and the annual work 12.5 million kWh per year. The power plant is operated as a storage power plant about eight hours a day. It drains directly into the bed of the river Oker. At this point, the designated on the Oker whitewater course, which is used mainly for Canoeing begins. From the irregular power plant operation resulting strong and sometimes abrupt changes in water level in the river Oker up to the equalization tank of Okertalsperre. The hydropower plant Romkerhalle is also known under the name " hydropower plant Oker ".
Oker - Grane studs
About the 7.4 km long Oker - Grane studs whose inlet is Romkerhalle and its outlet on the east bank of the Granetalsperre, water from the Okertalsperre ( power plant or bottom outlet ) can be passed into the Granetalsperre where it can be recycled for drinking water. The Granetalsperre itself only has a relatively small catchment area and is dependent for its drinking water to more inflows. The Oker - Grane tunnel was constructed in the period 1968-1970.
Balancing reservoir of Okertalsperre
The 3 km located below the dam in the Okertalsperre and 2 km downstream of the hydropower plant Romkerhalle equalization tank is equipped with a gravity dam, which has a height of 18 m. This tank can accumulate up to 204,000 cubic meters of water and is used downstream, especially the water level regulation. Directly below the dam there is no water power plant. To the northern edge of the Harz but several smaller hydroelectric power plants located on the Oker be fed. Similar to the Okerstausee forms when undisturbed water surface at the dam a very smooth water surface, on which the surrounding landscape clearly reflected. Because of the sheltered position of the balancing reservoir, this phenomenon there on quite frequently.
Balancing reservoir of Okertalsperre, impact body
Sewer
In order not to pollute the water in the dam, the resulting in Altenau and Schulenberg sewage is pumped into a separate sewer line to the Okertalsperre around the treatment plant Goslar- Oker.