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Diemelsee, Diemelstausee
Diemel dam: dam wall with reservoir, compensation pond and power station;  in front the village of Helminghausen, on the left the Eisenberg
Diemel dam: dam wall with reservoir, compensation pond and power station; in front the village of Helminghausen , on the left the Eisenberg
Location: District of Waldeck-Frankenberg ( HE ), Hochsauerlandkreis ( NW )
Tributaries: Diemel , Itter
Drain: Diemel
Larger places on the shore: Helminghausen , Heringhausen
Larger places nearby: Willingen , Brilon , Marsberg
Diemelsee, Diemelstausee (Hesse)
Diemelsee, Diemelstausee
Coordinates 51 ° 22 '20 "  N , 8 ° 43' 26"  E Coordinates: 51 ° 22 '20 "  N , 8 ° 43' 26"  E
Data on the structure
Construction time: 1912 to 1914 and 1919 to 1923
Height above valley floor: 36.2 m
Height above foundation level : 42 m
Height of the structure crown: 378.2 m
Building volume: 72,000 m³
Crown length: 194 m
Crown width: 7 m
Base width: 31 m
Power plant output: 1.04 MW
Data on the reservoir
Altitude (at congestion destination ) 376.2  m above sea level NHN
Water surface 1.65 km²dep1
Reservoir length 4 km (Diemelarm), 3.1 km (Itterarm)dep1
Reservoir width 300 mdep1
Storage space 19.9 million m³
Total storage space : 21.75 million m³
Catchment area 103 km²
Design flood : 113 m³ / s
Overflowing dam wall with power station building (from the north)

The Diemelsee, also called Diemelstausee and Diemeltalsperre , is a dam with 1.65 km² of water surface and about 19.9 million m³ of storage space on the Diemel . It is located in the municipality of Diemelsee in the Hessian district of Waldeck-Frankenberg and in the urban area of Marsberg in the North Rhine-Westphalian Hochsauerlandkreis ( Germany ).

The Diemeltalsperre (DiT) dam , which consists of a reservoir , dam wall , hydropower plant and compensation basin , is owned by the Federal Waterways and Shipping Administration ; Responsible is the waterways and shipping office Hann. Münden . Along with the Edersee , the Diemelsee is one of the water-regulating reservoirs in the Weser catchment area .



The Diemelsee lies in the northeastern foothills of the Rothaargebirge , the northeastern part of the Rhenish Slate Mountains . It spreads in the cross-border nature park Diemelsee mainly in the north Hessian district of Waldeck-Frankenberg in the municipality of Diemelsee; its small northern part and also its dam wall belong to the town of Marsberg in the Westphalian Hochsauerlandkreis. The Marsberg core city is about 13 km northeast (19 Diemel-km); Somewhat to the south-west is the Upland with the core town of Willingen just under 10 km (12 Itter-km) away .

The reservoir is traversed by the Diemel and fed by its tributary Itter . Its dam is about 500 m south of the village of Helminghausen (zu Marsberg). The only riverside village is Heringhausen (to Diemelsee) in the east. In addition to Marsberg, the next larger cities are Korbach (core city 14 km southeast; North Hesse) and Brilon (core city 9 km west-northwest; Westphalia), both of which are outside the catchment area of ​​the reservoir (which of course also applies to Marsberg, which is located below the lake) .

The Diemelsee is located in a wooded low mountain range , the highest mountain of which is the Köpfchen ( 610.4  m above sea  level ; west of the Itterarm), directly on the reservoir . Immediately east-southeast of the dam rises the Eisenberg ( 594.6  m ) and a few kilometers south of the Koppen reservoir ( 715.1  m ).

Natural allocation

The Diemelsee belongs in the natural spatial main unit group Süderbergland (No. 33) and in the main unit Ostsauerland Gebirgsrand (332) to the natural areas Vorupländer Hügelland (332.61; large part of the Diemelarm), which belongs to the subunit Vorupländer (Adorfer) Bucht (332.6), and Padberger Switzerland (332.70; entire Itter arm and the northern part of the reservoir near the dam), which is part of the Diemelbergland subunit (332.70).



The flora of the Diemelsee is presented in the bank areas, the inlets of the Diemel and Itter rivers and in the areas of the reservoir .



The fish stock of the Diemelsee is looked after and managed in cooperation with forest authorities. The fishing lease and the coordination of the fish stocking were largely handed over to the Diemelsee municipality as of January 1, 2019.


In the Diemelsee there is a population of river and pond mussels .


European beavers are present in the inlet areas of the Diemelsee. They were established from genetically Bavarian stocks.


Various types of water birds can be found at the Diemelsee. In addition, there are numerous typical species of the low mountain range Sauerland and Waldeck .

Protected areas

The northern part of the reservoir located in Westphalia near the dam is in the Hoppecke-Diemel-Bergland landscape protection area (landscape type A; CDDA no. 555554573; 2001; 77.9719 km²). Only the south-west end of the Itterarm of the Diemelsee in northern Hesse is protected as a nature reserve Diemelsee ( CDDA no. 81526; designated 1982; 18.69  km² in size). There, when the water level is low in summer, dry areas are characterized by pioneer corridors. They occur as mud flats and two-tooth societies. In the bank area there are reeds and dense willow bushes. Areas with quarry forest-like structures can be found along the Itter. Mallards , tufted ducks and great crested grebes breed by the lake . Little grebe , coot , goosander , gadfly , wigeon and pochard are resting water birds. Resting waders are regularly Sandpiper , less frequently Greenshank and Green Sandpiper. There have been beavers at the lake since 2015 .


The reservoir serves, with its dam, the water level control of the federal waterways Weser and Mittellandkanal , flood protection, hydropower generation and recreation.

On November 24, 1923, the damming of the Diemelsee began. In 2003, its previously specified capacity of 20.05 million m³ was re-measured using a laser scan process: its storage space (with normal full stagnation) is around 19.9 million m³ and its total storage space (with design flood ) around 21.75 Million m³. When it is fully blocked, its water surface is 1.65 km². The reservoir is a maximum of 34 m deep and its banks are about 16 km long. The storage target is 376.2  m above sea level and the design flood is 113 m³ / s. The catchment area of the dam is 103 km². The valley floor directly in front of the dam is at a height of exactly 342  m .

The southern Stauseearm is the Diemelarm, in addition to the zoom flowing from the south Diemel also from the direction of the village Stormbruch coming from the southwest Hagenbicke flows and on which the village Heringhausen is located; at the influence of the Diemel in the Seearm, the Holzbach flows from the southwest . The western one is the Itterarm, into which the Itter, coming from the southwest, flows and where Kotthausen (desert and hamlet of the village of Heringhausen) is located. The state border of Hesse and North Rhine-Westphalia runs slightly to the north of the point where the two arms meet.

Dam wall

Air or north side of the dam (view roughly from west to east)
Water or south side of the dam (view roughly from the southwest)


The dam of the Diemelsee was constructed according to the Intze principle as a curved heavy -weight dam made of around 72,000 m³ of rubble stones , which were mined in the specially set up diabase quarry on neighboring Eisenberg . The wall is a maximum of 36.2 m above the valley floor and 42 m above the foundation floor, resulting in a maximum height of 5.8 m above the valley floor. At the crown it is around 194 m long and 7 m wide. The base width is about 31 m. The crown is 378.2  m high.

Building history and modernizations

The construction work on the dam took place in two phases. The first phase lasted from 1912 to 1914. Then there was a break in the First World War (1914–1918) and a little beyond that. The second phase took place from 1919 to 1923. In 1924 the dam was put into operation.

In the 1990s, the dam was completely renovated and the safety standard was also adapted in accordance with DIN 19700 ( dams ). A sealing curtain with an injection seal was created in the ground, an inspection passage was installed and other work was carried out. The renovation work was completed in 1998. The Waterways and Shipping Office operates a Schirrhof on Lake Diemelsee for further maintenance and repair of the dam wall and storage area .

The dam is registered as a monument in the Marsberg list of monuments.

Second World War

The Diemelsee dam was attacked several times by the Allies during the Second World War (1939-1945) in order to destroy it and to damage or destroy the infrastructure below the wall through the leaking water. The wall was not destroyed.

At the end of the war, the Waffen-SS did not plan to demolish the wall, as US troops had already occupied the area around the reservoir at the end of March and the beginning of April and the German soldiers therefore had to move away. In April the US soldiers were replaced by Belgian soldiers and these in turn by British soldiers in June.

Helminghausen power plant

Helminghausen power plant from the air

The Helminghausen power plant is located below the dam . As a hydroelectric power station , it uses water from Lake Diemel. It went into operation in 1924, has two turbines , a nominal output of 1.04  MW and generates an average of 2.50 GWh of electricity per year  .

Compensation pond

Dam wall with Diemelsee and Heringhausen on the bank from the air

Just below the dam and power plant of the Diemel lake extends just south of Helminghausen an equalization pond called balancing reservoir ( 341.4  m ), which has m³ in normal operation approximately 65,000 storage space. It consists of a dam almost 8 m above the foundation level with an outlet structure , the crown of which is 343.2  m .


Itter level Kotthausen  III, (Itter zur Diemel, 377.68  m above sea level , kilometers: 3.40)

The waterways and shipping authority Hann. Münden operates several gauges to record the water level as well as the inflows and outflows of the Diemel reservoir. The water levels are recorded at the following points:

  • Inflow of the Diemel at the Wilhelmsbrücke gauge ,
  • Inflow of the Itter at the Kotthausen gauge ,
  • Reservoir level of the Diemel reservoir at the Diemeltalsperre gauge ,
  • Outflow into the Diemel at the Helminghausen gauge .

In the lower reaches of the Diemel no further officially accessible water levels are determined; From the difference between the water levels in Karlshafen and Wahmbeck, conclusions can be drawn about the contribution of the Diemel reservoir to the water flow of the Weser.

Tourism, leisure and sport

Sailboat on the Diemelsee in front of the Eisenberg and the dam crown

Over time, tourism has developed into one of the most important economic sectors in the Diemelsee area and the nearby Upland . The guests come from Kassel and the Ruhr area , and occasionally from the Netherlands . Tourist associations were founded in the villages on and near the reservoir to promote tourism, which still plays a crucial role today. In order to better connect the region, the Korbach-Bredelar bus line, founded in 1922, was diverted to the reservoir.

The Diemelsee now serves as a leisure and recreation area. Activities and sports include:

  • Fishing
  • Excursion on the passenger ship MS Muffert , named after the St. Muffert lookout point
  • Swimming (e.g. at the Heringhausen lido)
  • canoeing
  • swim
  • Sailing and surfing
  • Hiking:
    South and east past the Diemelsee, the
    Diemelsteig leads, among other things, over the Eisenberg and the St. Muffert vantage point there . The Drei-Seen-Weg ( Edersee –Diemelsee– Twistesee ) runs past north ; a circular variant of this path runs around the reservoir.
  • Diving (e.g. in a bay near the dam on the Westphalian side)


Immediately east of the Diemelsee, coming from the north of Helminghausen , the Westphalian state road  912 runs along the western flank of the Eisenberg , which turns south - also running along the reservoir - into the north Hessian state road 3078 and there to Heringhausen . From the latter, in Heringhausen, the district road  65 branches off, which was laid out along the Diemelarm, crosses it and leads south-west to Stormbruch . From the K 65 branches off to the southwest of Heringhausen, the K 71, which runs along the southern part of the Diemelarm and then further south-southeast to Giebringhausen . The L 393 runs along the north bank of the Itterarm from Helminghausen in the northeast to Bontkirchen in the southwest.


View from the
St. Muffert vantage point on the Eisenberg over the Diemelsee: left Heringhausen on the Diemelarm, in the middle Stormbruch before Koppen on the horizon, right the Itterarm with Kotthausen

See also


  • Peter Franke, Wolfgang Frey: Dams in the Federal Republic of Germany . Published by the National Committee for Large Dams in the Federal Republic of Germany (DNK) and the German Association for Water Management and Culture Building e. V. (DVWK), Systemdruck-GmbH, Berlin 1987, ISBN 3-926520-00-0 .
  • Paul Gerecke: The Diemeltalsperre , in Zeitschrift für Bauwesen , 75th year, 10. – 12. Heft (engineering component), 1925, pp. 93–124, on opus.kobv.de ( PDF ; 4.56 MB)

Web links

Commons : Diemelsee  - collection of pictures, videos and audio files

Individual evidence

  1. a b c d e f g h i j k l m n o Wasserstraßen- und Schifffahrtsamt Hann. Mouths; Dams : Edertalsperre and Diemeltalsperre on wsv.de.
  2. a b c d e f g h i j k l Paul Gerecke: Die Diemeltalsperre , in Zeitschrift für Bauwesen, 75th year, 10. – 12. Heft (engineering component), 1925, pp. 93–124, on opus.kobv.de (PDF; 4.56 MB)
  3. DIN 4048-1 Hydraulic Engineering, Terms, Dams, January, 1987
  4. Martin Bürgener: Geographical Land Survey: Handbook of the natural spatial structure of Germany # single sheets | The natural spatial units on sheet 111 Arolsen. Federal Institute for Regional Studies, Bad Godesberg 1963. →  Online map (PDF; 4.1 MB)
  5. More protection for the mussels from Diemelsee ( Memento from April 5, 2019 in the Internet Archive )
  6. Network fishing, beavers gnaw at the Diemelsee ( Memento from April 5, 2019 in the Internet Archive )
  7. ^ Karl Schilling, Westfalenpost, More protection for the mussels from Diemelsee ( Memento from April 5, 2019 in the Internet Archive ), on diemelsee.de
  8. Karl Schilling, WLZ, beavers gnaw at the Diemelsee ( memento from April 5, 2019 in the Internet Archive )
  9. Map services of the Federal Agency for Nature Conservation ( information )
  10. Diemelsee nature reserve , on nabu-waldeck-frankenberg.de
  11. Giebringhäuser Walter Emden photographs Biber an der Diemel with a wildlife camera , Waldecker Landeszeitung from November 24, 2017
  12. a b On November 24, 1923, the damming of the Diemelsee began , from November 25, 2013, on hna.de.
  13. Overview of the sights in Marsberg . (PDF; 205 kB) Helminghausen district . Tourist office Marsberg e. V., November 30, 2010, accessed June 6, 2011 .
  14. ^ A b c Hugo Cramer: The district of Brilon in the Second World War 1939–1945, 1955, section Helminghausen, pp. 97–98
  15. uniper equity story appendix (archived). (pdf; 5.4 MB) (No longer available online.) eon.com, April 26, 2016, archived from the original on October 28, 2016 ; accessed on December 17, 2017 (English). , P. 76
  16. a b Topographical Information Management, Cologne District Government, Department GEObasis NRW ( Notes )
  17. a b c d Wasserstraßen- und Schifffahrtsamt Hannoversch-Münden: current level (pegelonline.wsv.de):
      Wilhelmsbrücke , Kotthausen , Diemeltalsperre and Helminghausen
  18. MS Muffert timetable with details of the ship's name on seerundfahrten-diemelsee.de
  19. Strandbad Diemelsee ( Memento from April 10, 2013 in the Internet Archive ), on diemelsee.de