Sparrowhawk Dam
The Sperberhaier Damm is an aqueduct of the Upper Harz water shelf . It was created in the 18th century and served to channel the water from the dam ditch over the sparrowhawk shark basin on the Clausthal plateau. This was intended to cover the rapidly increasing demand for power water for the water wheels of the Clausthal mines. The water flowed in a run on the top of the dam. The hydraulic output was up to 1000 liters per second at peak times. An open channel is now only visible at the western end.
The B 242 runs immediately south of the Sperberhaier Dam . The B 498 joins the B 242 roughly in the middle of the dam . Both federal roads then run together to the eastern end of the dam, where the B 498 then turns towards Altenau .
Like all buildings in the Upper Harz Water Regale includes the Sperberhai Dyke since 2010 to UNESCO - World Heritage Site .
history
According to tradition, it was planned as early as 1656 to channel water from the Bruchberg to the Clausthal plateau and there, above all, to the Upper Hausherzberger pond. At that time, work began on the construction of the Long Trench , which was created from the Upper Hausherzberger pond with the usual gradient of less than 1 ‰ in the direction of Bruchberg. Obviously it was only noticed during the construction work or during the parallel survey that there was a saddle between the Bruchberg and the Clausthal plateau that could not be overcome with this technique. Even then, the idea quickly arose of overcoming this depression with a 23 m high and over 2 km long dam on which the trench would then be led. But this dam was so huge that it seemed impossible to build.
The subsequent discussion about technical alternatives dragged on for almost 100 years. The obstacle could also have been bridged with a wooden hammer , but it was known that these weathered quickly and, in addition, wood was an extremely scarce commodity at the time due to the enormous demand for wood of the mines and steelworks. A culvert , i.e. a pipeline, was also discussed, but until then, people only had experience with pipes up to around 50 mm in diameter and did not know how to dimension a pipeline with a capacity of around 100 liters per second. As an experiment, the project would have been decidedly too expensive.
The alternative of constructing an aqueduct as a stone bridge was never discussed. Presumably one knew that there had been bad experiences with the Altväterbrücke in Freiberg with a comparable building. Under the Central European weather conditions (frost), Roman designs have not particularly proven themselves.
In the 1720s, the water shortage in the Clausthal mines worsened considerably. At that time, the mountain master Andreas Leopold Hartzig (1685–1761) suggested that the almost 8 km long stretch between Sperberhai and Clausthal should only be bridged with half of the usual gradient. By creating a new ditch from Clausthal to the sparrowhawk shark with half the slope, the sparrowhawk shark was reached at about 7 m lower level. As a result, the dam only had to be piled up 16 m high and its crest was only 940 m long. Such a structure was affordable, even if it still required a huge effort.
The implementation took place in the years 1732–1734. On average, 200-300 workers were employed, at peak times even 500 to 600. Commissioning took place in July 1734; in October 1734 a kind of official inauguration ceremony took place in the presence of the miner captain .
Accidents and optimizations
During the almost 300 years of operation, there were several accidents on the huge, but also sensitive structure: On the one hand, the seepage of large amounts of water from the trench into the dam body could cause erosion or ground fractures ; on the other hand, the ditch on the dam crest could overflow during floods and cause something similar. In both cases, significant earthworks were required to repair the damage. The first damage of this kind occurred in the year of inauguration 1734, the last in 1978.
Originally, the trench on the dam crest was enclosed in dry masonry; Sealed with turf or clay on the left and right and under the sole. In 1871 this trench was replaced by a concrete barn 2 m wide and 1 m high; this was probably one of the first major uses of Portland cement in the Harz Mountains. Due to this generous size, the trench was able to carry a water volume of up to 1000 liters per second over the sparrowhawk shark, despite the very low gradient (about 20 cm over 900 m in length). The 1978 accident was probably due to leaks in this concrete compound, which had cracked as a result of the dam's subsidence.
In 1981 the Sperberhaier Dam was piped with an AZ pipe with a diameter of 500 mm in order to rule out a repetition of the accident of 1978. As a result, the dam not only lost its great hydraulic capacity, but also its aqueduct character.
In order to restore the aqueduct character, the Harz waterworks reversed the piping on the last 300 m of the Sperberhaier Dam in 1992 and restored something like the type of ditch that probably led the water over the dam around 1734.
Others
In order to lift part of the water into some of the higher Upper Harz ponds , the Polsterberger Hubhaus was built on the Polsterberg (about 3 km west of the Sperberhaier Dam) .
At the eastern end of the dam is the former Dammhaus . It was built in 1732 as a construction office, was then the accommodation of the responsible trench attendant until the 1970s and is now a well-frequented restaurant.
See also
literature
- Martin Schmidt : The water management of the Upper Harz mining (= publication series of the Frontinus Society . Issue 13). 3rd supplemented edition. Harzwasserwerke, Hildesheim 2002, ISBN 3-00-009609-4 , p. 29-78 .
- Martin Schmidt : The cultural monument of the Upper Harz water shelf . Harzwasserwerke, Clausthal-Zellerfeld 2005 ( PDF, 28 pages, 1.7 MB ( memento from July 19, 2011 in the Internet Archive ) pages 16 + 17).
Web links
Coordinates: 51 ° 46 ′ 49 ″ N , 10 ° 25 ′ 12 ″ E