Lake Constance water supply

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Lake Constance water supply

legal form Administration union
founding October 25, 1954
Seat Stuttgart , Germany
management Michael Stäbler (commercial)
Christoph Jeromin (technical)
Number of employees 320
sales 74.0 million euros (2015)
Branch Water supply

The Bodensee-Wasserversorgung (BWV) is a special purpose association based in Stuttgart , which was founded on October 25, 1954 by 13 municipalities to cover the water requirements in many municipalities in the arid Swabian Alb and in the greater Stuttgart area. In 2015, as one of the largest German long-distance water supplies, it supplied around four million people in around 320 cities and towns with drinking water from Lake Constance .


Water withdrawal

Aerial photo of the treatment plants of the Lake Constance water supply on the Sipplinger Berg

Every year between 125 and 130 million cubic meters of water are taken from Lake Constance by the Lake Constance water supply. That is a little more than one percent of the total flow and less than Lake Constance loses through evaporation. The water discharge in 2015 was 131 million cubic meters. The highest annual output was reached in 2003 with 139.8 million cubic meters. On August 8, 2003, the highest daily output was measured at 531,000 cubic meters. The Lake Constance water supply has a withdrawal right of 670,000 cubic meters of raw water per day; that's an average of 7750 liters per second. This was already regulated in 1966 in an international agreement between the neighboring states of Austria , Switzerland and the Federal Republic of Germany. The drinking water supplied by the Bodensee water supply has a hardness of 1.6 millimoles calcium carbonate per liter (formerly 9.0 degrees German hardness), the pH value is 7.9 and the nitrate content is 4.2 mg / l (2015 ).

Two thirds of Lake Constance is fed with water from the Alps . In total, the tributaries provide around 11.5 billion cubic meters of fresh water per year. The annual water withdrawal of the Lake Constance water supply of around 125 to 130 million cubic meters of water is, compared to the inflow, a negligible amount. Most of the water from the Alps flows into the lake from an altitude of more than 1500 meters and its quality is practically unaffected by settlement, industry and agriculture. A simple, natural treatment is therefore sufficient for use in drinking water. Thanks to the constant inflow from the Alps, there is always enough water available.

Due to the large water volume of almost 50 cubic kilometers (50 billion cubic meters = 50 trillion liters), the water is well protected in the event of an accident involving substances that are hazardous to water, as pollutants are diluted so much that they could not impair the drinking water supply. The low concentrations would not significantly pollute the water and even in the raw water would remain well below the strict limit values ​​of the Drinking Water Ordinance. In addition, the treatment would prevent such substances from getting into the drinking water.

The lower water layers in Lake Constance (up to 254 meters deep) and also in Überlinger See (up to 147 meters deep) are protected from contamination by the natural stratification of the water. On the four to five degrees Celsius cool deep water, a warmer layer floats almost all year round, which due to its lower density hardly mixes with the deep water. If pollutants get into the upper layer, they cannot sink to the depth from which the Lake Constance water supply draws its water. The cool deep water also means protection against bacterial contamination. It is only at the end of winter that the stratification is lifted and the water is circulated. This is very important for the lake because it supplies the deep area with oxygen.

Coverage area

Headquarters in Stuttgart-Vaihingen

The association has 183 members, including 149 cities and municipalities and 34 water supply associations. A total of 320 cities and municipalities are supplied in this way.

The supply area extends from the Lake Constance area in the south to Bad Mergentheim in the northeast of the state of Baden-Württemberg. It includes the central Neckar area as well as areas of the Baar , the Swabian Alb , the Black Forest , the Stromberg , the Heilbronner Unterland, the Kraichgau and the Odenwald up to near the Hessian and Bavarian border in the north.


Source pot on the Sipplinger Berg

Since 1958, the water has been taken from Lake Constance near Sipplingen at a depth of 60 m through two pipes, and since 1978 three pipes, and pumped to the Sipplinger Berg 310 m higher in the Süßenmühle lake pumping station.


On the Sipplinger Berg, the drinking water is treated by microsieves, ozone and Fe (III) salt-supported sand filtration, and then chlorine gas is added for disinfection. Every month 60 water samples are examined in the laboratory using a mass spectrometer. Trace substances such as sweeteners, antidiabetic agents, heat protection agents and X-ray contrast agents can be detected.

Water transport

From the Sipplinger Berg, the water is channeled through two main and numerous secondary and connecting pipes with internal diameters of up to 2.25 m to the connected cities and communities. The original pipes were made of gray cast iron , which leaked and broke over time and will gradually be replaced by steel pipes in the 21st century.

Most of the water flows freely downhill to Mosbach in the southern Odenwald ; In addition, 17 pumping stations ensure sufficient pressure in the network and transport the water to higher-lying communities. To support this, 20 pressure increase systems can cover the higher water demand at peak times.

Main line 1 from 1958 carries the water up to a height of 753 meters near Liptingen ( ). From there it flows into the Schwarzwald-Baar district and the Neckar area to Ludwigsburg . World icon

Main line 2 from 1971 crosses the Swabian Alb through the approximately 24 kilometers long underground "Albstollen" . It supplies Stuttgart and the northern part of Baden-Württemberg. The machine used at the time for tunneling is now exhibited in the German Mining Museum in Bochum . The construction of the pipeline (1968–1970) under the direction of Fritz Schmidt was an outstanding technical achievement at the time.

With the commissioning of the West pipeline from Schönaich to Sternenfels in 2003, the last bottlenecks were eliminated.

The pipe network has a length of around 1700 km.

Water tank

Reservoir on the Sipplinger Berg

29 water tanks with a total volume of 470,600 m³ are integrated into the pipe network. The largest of these is the elevated tank in the Stuttgart district of Rohr ( ) with a capacity of 100,000 m³. World icon

  • Main line 1
    • Sipplinger Berg: 112,000 m³ at 689.4  m above sea level. NHN
    • Liptingen apex tank : 50,000 m³ at 753.5  m above sea level. NHN
      • Türnleberg elevated reservoir , north of Bad Dürrheim
      • Elevated tank Wanne, Villingen
      • Elevated container corners
      • Rote Steige elevated tank
    • Zepfenhan elevated tank : 10,000 m³ at 706  m above sea level. NHN
    • Irrenberg elevated tank
      • Egert elevated tank
    • Wessingen elevated tank : 15,000 m³ at 640  m above sea level. NHN
    • Öschingen elevated reservoir : 15,000 m³ at 598  m above sea level. NHN
    • Elevated tank pipe: 100,000 m³ at 526  m above sea level. NHN
    • Elevated tank Hohe Warte : 30,000 m³ at 432  m above sea level. NHN
  • Main line 2
    • Sipplinger Berg: 112,000 m³ at 689.4  m above sea level. NHN
    • Büttnau tunnel inlet tank: 39,000 m³ at 651.8  m above sea level. NHN
      • Disk summit elevated tank
      • Nonnenbrunnen elevated tank
    • Elevated tank pipe: 100,000 m³ at 526  m above sea level. NHN
    • Elevated tank Hohe Warte: 30,000 m³ at 432  m above sea level. NHN
    • Schweinsberg elevated tank : 24,000 m³ at 373.2  m above sea level. NHN
    • Hardhof elevated tank
    • Rehberg elevated tank
The first elevated tank in Liptingen with a capacity of 20,000 cubic meters was created by the Sigmaringen company Steidle and put into operation in autumn 1958. When it turned out to be too small, a second container with 30,000 cubic meters was completed in the spring of 1962 by the Härer company from Schwäbisch Hall . The supply line for the interconnected tanks consists of Mannesmann pipes 18 meters long and 1.30 m in diameter, while the drainage is through concrete pipes with a steel jacket.

Water price

The Bodensee water supply is a special purpose association. She doesn't make a profit. The association members, who are both owners and customers of Lake Constance water supply, offset the actual costs through a so-called allocation (fixed costs and operating costs). The costs are calculated for delivery to the community's elevated tank. They consist of fixed costs for the amount of water ordered and costs for the amount of water actually used.

The average surcharge in 2016 was 56.4 cents per 1000 liters. This surcharge also includes 8.1 cents of water abstraction fee. The fixed assets of the Lake Constance water supply are 744.5 million euros (2015), the annual turnover is 74 million euros (2015).

Emergency power generators against power failures

In the event of a power failure , the water supply is secured by three emergency power generators. 180,000 liters of heating oil are stored for the self-sufficient operation of the diesel engines.


BWV building in Sentenhart
BWV building in Ringgenbach

After the Second World War there was a water shortage in many communities in Baden-Württemberg. The years 1947 and 1949, when it rained little, were particularly bad. In addition, there was the “ economic miracle ” that began in the 1950s and caused the demand for water to grow very quickly. As early as 1950, a study commission for water supply of the Württemberg-Baden city association was set up. In February 1953, she suggested using Lake Constance to supply drinking water; In July 1953 the planning association was founded. In addition to Stuttgart , twelve other cities and communities ( Böblingen , Ebingen , Hechingen , Kornwestheim , Leonberg , Reutlingen , Rottweil , Schwenningen , Sindelfingen , Tailfingen , Tübingen and Villingen ) belonged to it. After the construction costs and their payment had been clarified by the cities and municipalities, the Lake Constance Water Supply Association was founded on October 25, 1954.

On February 11, 1956, construction work began on the conveying and processing systems on Lake Constance and the first main line from Lake Constance to Bietigheim . 1200 property owners were affected by the construction of the long-distance water pipeline. A total of 3,000 workers were employed on what was then Europe's largest construction site. After only two years and eight months, operations began on October 16, 1958. This started a rapid development. The network was constantly expanded and expanded to meet the water needs of other regions.
A special feature of the pipe network is the around 24 kilometers long underground crossing of the Swabian Alb, the so-called "Albstollen".

Up to August 31, 1959, when 30 cities and municipalities were affiliated to the association, a total of 22.5 million cubic meters of Lake Constance water was transported and transported.

In 1981 the Bodensee water supply merged with the long-distance water supply Rheintal (FWR), which supplied the areas north of Heilbronn as well as many towns and communities near Mosbach, Buchen, Walldürn and Bad Mergentheim. As a result, Lake Constance water supply gained 54 cities and municipalities as well as ten new water supply associations. The total number of members rose to 150.

In 2015, the Bodensee water supply supplied a total of 320 cities and municipalities with around four million inhabitants with drinking water through its 143 members.

Cross-border leasing agreement 2002–2009

With a cross-border leasing contract, the association leased all of its operating facilities and infrastructure to a US trust company for 841 million US dollars and at the same time rented it back from the latter. The contract ran for 30 years. The money was deposited with various financial institutions, with the obligation to repay the rental price of the Lake Constance water supply in several installments. One of the financial institutions involved, AIG , had to be replaced in the course of the financial crisis in autumn 2008 because it had fallen below a credit rating stipulated in the contract . At the end of March 2009, the contractual relationships were terminated prematurely. The loss from the business amounts to 4.7 million euros.

Poison attack in 2005

Drinking glass

On October 18, 2005, a poison attack on Lake Constance was reported in a letter to the Bodensee water supply. During the search for possible pollutants, two five-liter canisters were found on November 7th, one filled with atrazine , the other with a mixture of other pesticides. On November 9th, the canisters were recovered not far from the drinking water extraction point at a depth of around 75 meters and around 300 meters from the shore. After further searches on the bottom of the lake, two more containers were located on December 10th and were recovered on December 12th. It was a further five-liter canister with liquid pesticides and an opened plastic bag with granules - according to an analysis by the State Criminal Police Office, also a pesticide. The limit values ​​of the Drinking Water Ordinance were never exceeded in the drinking water, which was shown by corresponding control examinations. In mid-January 2006, the search operations on the lake bottom were discontinued without any further findings. Since the size of Lake Constance alone dilutes the pollutants very much, there was no serious danger to the drinking water supply. Nevertheless, the safety measures for the Lake Constance water supply have been increased through even better monitoring of the drinking water intake and the company's own systems. In addition, with effect from January 26, 2012, a restricted zone of approx. 400 × 1800 m approx. 100 m in front of the bank was set up above the extraction point, within which driving, swimming and diving are prohibited.


The Zweckverband Bodensee-Wasserversorgung is a member of the Arbeitsgemeinschaft Wasserwerke Bodensee-Rhein (AWBR) and works in the International Water Protection Commission for Lake Constance (IGKB) .

See also


  • Strong together. In: Crystal clear. The magazine of Lake Constance water supply, June 2009, pp. 4–7.
  • Zweckverband Bodensee water supply (ed.): Drinking water for Baden-Württemberg. Brochure dated September 2008.
  • Gerhard Naber: 30 years of Lake Constance water supply , in: Writings of the Association for the History of Lake Constance and its Surroundings , 107th year 1989, pp. 251–272 ( digitized version )

Web links

Commons : Bodensee water supply  - collection of pictures, videos and audio files

Individual evidence

  1. Numbers and facts. Lake Constance water supply, accessed on October 3, 2017 .
  2. a b c Luisa Rische, Katy Cuko: water supply. Laboratory boat not seaworthy . In: Südkurier of April 11, 2015
  3. Drinking water studies Lake Constance water supply, n. D.
  4. Mona Lippisch: This is how laboriously trace substances are detected in Lake Constance water. In: Südkurier , November 27, 2019.
  5. Villingen-Schwenningen water pipes are being renewed By Birgit Heinig July 4th, 2018, Schwarzwälder Bote
  6. Zweckverband Bodensee-Wasserversorgung (Ed.): Drinking water for Baden-Württemberg. Prospectus dated September 2008. Section water distribution
  7. ^ Alfred Eble: The top-level tank of the Lake Constance water pipeline in Liptingen . In: "HEGAU - magazine for history, folklore and natural history of the area between the Rhine, Danube and Lake Constance". Issue 1 (13) 1962. Page 115
  8. Strong together. In: Crystal clear. The magazine of Lake Constance water supply, June 2009, p. 6.
  9. Home chronicle . In: Hegau - magazine for history, folklore and natural history of the area between the Rhine, Danube and Lake Constance . Self-published by the Hegau history association Singen e. V., Issue 2 (8) 1959, p. 259.
  10. BWV: Cross-border leasing is history . News from April 9, 2009 ( Memento of February 12, 2017 in the Internet Archive ) (PDF; 86 kB) Retrieved on February 11, 2017
  11. No evidence of perpetrators in the case of the Lake Constance poison attack. In: Salzburger Nachrichten of November 15, 2005
  12. New restricted zone around the water supply point on Lake Constance. In: Schwäbische Zeitung from January 25, 2012

Coordinates: 47 ° 48 ′ 26 ″  N , 9 ° 6 ′ 12 ″  E