Wahnbach dam
| Wahnbach dam | |||||||
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| Coordinates | 50 ° 48 '17 " N , 7 ° 17' 3" E | ||||||
| Data on the structure | |||||||
| Construction time: | 1954 to 1958 | ||||||
| Height above foundation level : | 52.5 m | ||||||
| Height above the river bed : | 46 m | ||||||
| Height of the structure crown: | 126.1 m | ||||||
| Building volume: | 1 020 000 m³ | ||||||
| Crown length: | 379 m | ||||||
| Crown width: | 7.55 m | ||||||
| Slope slope on the air side : | 1: 1.5 - 1: 1.75 | ||||||
| Slope slope on the water side : | 1: 2 - 1: 2.5 | ||||||
| Data on the reservoir | |||||||
| Altitude (at congestion destination ) | 124 m | ||||||
| Water surface | 2 km² | ||||||
| Reservoir length | 5.8 km | ||||||
| Storage space | 41 300 000 m³ | ||||||
| Total storage space : | 43 180 000 m³ | ||||||
| Catchment area | 69 km² | ||||||
| Design flood : | 110 m³ / s | ||||||
The Wahnbachtalsperre is located in Siegburg- Seligenthal in the Rhein-Sieg district in North Rhine-Westphalia and is used to supply drinking water . The reservoir is mainly fed by the Wahnbach .
The dam and the drinking water supply were put into operation on April 28, 1958 by then Prime Minister Fritz Steinhoff . The Wahnbachtalsperrenverband (WTV), founded on June 12, 1953, supplies more than 780,000 residents in the federal city of Bonn , in the Rhein-Sieg district and in the district of Ahrweiler with drinking water, although this is partly done with groundwater from the lower Sieg area .
The dam's barrier structure is a 52.5 m high dam .
history
Before the Wahnbachtalsperre was built, the "Lüttersmühle", the inn "Wahntaler Schweiz" (both about 50 ° 50 ′ 12.9 ″ N , 7 ° 18 ′ 32.4 ″ E ), two agricultural ones , were in today's storage space Property - "Hillenbach" (approx. 50 ° 50 '12.6 " N , 7 ° 18" 27.8 " E ) and" Petershof ", which stood on the site of the former Hoffnungsthaler Hütte (approx. 50 ° 49' 8" N , 7 ° 18 ′ 20 ″ E ). The residents of these houses had to be relocated. The "Herkenrather Mühle" restaurant was located at the entrance to the Wahnbach, where the current pre-lock is located. The building was used by the Wahnbachtalsperrenverband (WTV) for several years as a test facility for phosphorus elimination systems.
The purpose of the dam should be:
- the delivery of supplementary water in the event of low water levels in the Sieg
- the generation of hydropower
- the flood protection in the lower Wahnbachtal and
- the supply of Bonn, Siegburg, the Siegkreis and the district of Bonn with drinking water and the industrial company based in Siegburg, the chemical fiber AG, with process water
The water rights granted on November 12, 1955 allow an annual extraction of 28.1 million cubic meters.
The pictures compare the state before and after the construction of the reservoir. In the map from 1951, the Wahnbachtalstraße leads along the Wahnbach to today's L189 near Herkenrath. After the flooding caused by the construction of the dam, the course of the stream and the road in the reservoir disappeared. At the northern and southern ends of the lake there are remains of the road, and between Wolperath and Wahn former feeder roads. The Ummigsbach Bridge , built between 1925 and 1927 , was blown up in 1945 by the Wehrmacht.
Course of the Wahnbach and the Wahnbachtalstraße around 1950 and overlaying today's reservoir.
Bridge of the old Wahnbachtalstraße, which is normally flooded by the Wahnbachstausee.
Course of the old Wahnbachtalstraße.
Ummigsbach Bridge in the lower reaches of the Wahnbach around 1930.
After it was blown up by the German Wehrmacht in 1945, the bridge is in ruins.
geology
According to the geological map of the Geological Service of North Rhine-Westphalia, the surrounding layers consist of the Siegen layers , at Neunkirchen-Seelscheid also layers of the Ems. On the mountain tops, these paleozoic layers are mostly covered by Quaternary loess .
The Siegen layers are fossil-bearing in places. In the widespread alternation of sandstone and slate layers, these mostly occur in clayey layers.
These fossils are very valuable from a paleobotanical point of view, as they provide insights into the flora of the Lower Devonian. Species found here include A. Taeniocrada decheniana , Sciadophyton laxum , Sawdonia and Stockmansella langii . The latter species in particular formed reed-like stocks at that time.
Other locally limited layers are the Oligocene to Miocene basalts and basalt tuffs of the Steimelskopf. Quaternary drifting sands and, further east, main terrace gravel occur in the vicinity of heather.
construction
The structure of the dam consists of a bottom outlet tunnel, extraction tower, hearth wall control tunnel and the actual barrier structure. The dam was built from a pile of Grauwacke that was extracted from a valley slope near the village of Pinn. This got an outer skin seal made of asphalt concrete. The remaining structures were made of concrete. In January 1955, work began on the dam structure. Between April and August 1955, work was carried out on the hearth wall control tunnel, on the water-side dam foot and the flood relief with the weft channel and the 8 m deep stilling basin . So that the Wahnbach did not lead to flooding during the construction work, it was led past the dam structure through a diversion tunnel. This tunnel now houses the raw water pipe from the extraction tower, which allows extraction in three water depths (20, 25 and 30 m above the foundation level). The bottom drainage tunnel with heights of 0 and 10 m above the foundation level offers two further water extraction options.
From September 1955 to June 1956, the dam structure was built by pouring stone rubble. The daily output was 8,600 m³. The topping-out ceremony was celebrated on June 19, 1956. The surface sealing with asphalt concrete was then applied on the water side within five months. On December 20, 1956, the dam of the Wahnbach was started by closing the butterfly valves.
In the lake itself there is a platform with a ventilation system. Using a periscope , air can be pumped into different water depths and thus the oxygen content of the water can be influenced.
Below the barrier there is a machine house with pumps for pumping the raw water to the Siegelsknippen drinking water treatment plant, as well as another one that contains systems that are used to reduce the carbonic acid content of the groundwater from the Hennef Siegbogen, which is also below the dam.
Pre-lock
At the upper inlet of the Wahnbachtalsperrensee, near the "Herkenrather Mühle", there is another barrier structure - the pre-dam. Here the water for the main basin is pre-clarified in a phosphorus elimination system.
Intensive agricultural fertilization and use of the areas in the catchment area of the Wahnbach resulted in a mass development of algae in the reservoir and threatened eutrophication of the lake. The reason for this was the released nutrients, mainly due to the high concentration of phosphorus. The extensive pre-treatment of the tributaries deprives the algae of their livelihood and reduces the biomass produced in the reservoir. For this, the phosphorus compounds are reduced, the mineral turbidity and organic compounds are removed and algae and plankton are reduced. Initially, a test facility was started in the "Herkenrather Mühle". This had a throughput of 1 m³ / h. Today the plant has a throughput of approx. 18,000 m³ / h. The pre-basin has a usable storage volume of approx. 500,000 m³ and the dam has its own flood overflow.
Security and flood protection
Reservoirs with their shut-off structures play a special role in terms of monitoring during operation. Due to its construction and location, each dam must be viewed as an individual structure. An individually adapted monitoring system is required for this. The monitoring takes place in coordination with the state supervisory authority. In North Rhine-Westphalia this lies with the state environmental agencies. The last major overhaul was carried out in autumn 2006, for which the water level had to be lowered significantly.
The dam structure is protected from flooding by a flood relief system and the bottom drainage tunnel with two pipes with a diameter of 1400 mm, which, like the chute , open into the stilling basin .
In addition to the production of drinking water, flood protection is an important task of the dam. In order to be able to absorb the flooding that occurs, a storage volume is specified that must be kept free for a prescribed period. These are the months between November and March. A volume of 2 million m³ is to be reserved for the Wahnbach dam. If the volume is fully used and the inflow continues to be constantly high, the excess water is drained to the underwater in a controlled manner via the flood relief system.
Water catchment areas
The main water catchment area of the Wahnbachtalsperre lies between Wiehl-Drabenderhöhe in the northeast, Hennef / Much in the southeast and Siegburg / Seelscheid in the northwest. It is mainly fed by the Wahnbach with its tributaries, including the Wendbach.
A groundwater works in the Hennef Siegbogen area and the Untere Sieg groundwater works in Meindorf serve for further water extraction .
Wahnbach dam
The average reservoir volume is 34 million cubic meters per year. The water law allows an annual extraction of 28.1 million m³ from the dam. This means that there is a secure reserve. The water quality is influenced by the inorganic parameters of the phosphorus concentration; this is already low in the Wahnbach and the other tributaries and tends to continue to decline.
Lower victory
On March 3, 2000, the association was granted a permit under water law to extract 20 million m³ / year for a period of 40 years. The groundwater is obtained by means of three horizontal wells and processed in a plant in Sankt Augustin-Meindorf. The groundwater levels are monitored regularly: weekly at 82 measuring points, monthly at 103 measuring points and every six months at 207 measuring points.
Hennef victory arch
On May 11, 1978, the association was granted the water law permit for the extraction of 13.3 million m³ / year for this area. Here the drinking water is obtained by means of two horizontal filter wells, then passed to the foot of the dam, where a large part of the carbon dioxide is degassed and finally, like the surface water from the dam, is processed into drinking water in the treatment plant Sieelsknippen. The permit under water law is valid until December 31, 2008. Here, too, the groundwater level is observed in many places. Weekly at 46, monthly at 65 and every six months at 161 measuring points.
The groundwater flow and the groundwater levels are influenced by the water levels of the Sieg and Rhine as well as the geomorphology of the groundwater-bearing subsoil. The extraction wells create a recognizable lowering funnel in the groundwater table, but it is only small. The raw water quality of the groundwater depends on the nitrate concentration and has a downward trend. There is a water protection area around the water extraction systems . This is divided into different zones.
Drinking water treatment
When treating reservoir water to make drinking water , all ingredients contained in the reservoir water that must not be contained in the drinking water must be removed. The unwanted ingredients enter the reservoir water from the tributaries of the dam or are formed here through the growth and degradation of algae and other aquatic organisms.
The undesirable ingredients in dam water include:
Dissolved substances
- Decomposition products of fungi, bacteria and algae (sometimes toxic, odorous substances, interfere with disinfection)
- Iron and manganese (non-toxic, brown-coloring substances, interfere with disinfection)
- Humus substances (non-toxic, brown substances, interfere with disinfection)
- Mineral oils, solvents, components of cleaning agents (partly toxic, odorous substances)
- Plant protection products (toxic substances)
Particles and turbidity
- Pathogens from sewage and animal faeces
- living or dead fungi, bacteria, algae, aquatic animals (sometimes toxic, odorous substances, interfere with disinfection)
- mineral turbidity from runoff
The drinking water treatment plant of the WTV is in Siegburg-Siegelknippen. It is about 100 meters above the Wahnbach valley. One focus of the water treatment lies in the more developed by the Association of flocculation and the substantially newly developed from WTV disinfection by ultraviolet light and ultrasound .
Mixing in flocculants, usually iron (III) chloride , creates large flakes that are supposed to bind as much fine substances as possible from the raw water . These are then filtered out by the sand filters. Ultrasound treatment deactivates the plankton in the water so that it can be easily filtered out. If this does not happen, it can detach itself from the flakes and so penetrate the filter.
The filters consist of several layers: a layer of quartz sand approx. 0.8 m and a layer of anthracite coal with 1.2 m. In the so-called backwashing process, the filtered substances are rinsed out and deposited in the mechanical sedimentation system. The raw water is now fed into an intermediate storage tank. From there it goes to the UV disinfection (an innovation in the field of disinfection and mainly developed by the WTV - chlorine dioxide was used here in the past). By irradiating the microorganisms in the water with UV light of 400 J / m², all hygienically relevant microorganisms are recorded and rendered harmless. The process is now approved according to Part II of the list disinfection process (Bundesgesundheitsblatt 10/2002 p. 842).
The water is constantly examined by our own accredited laboratory. Furthermore, the WTV operates the first and so far largest test rig for UV disinfection devices up to 3000 m³ / h in the Meindorf waterworks and works together with the DVGW. In this test bench, some large and small systems for the USA, Germany, France and Canada were tested.
Drinking water quality
The chemical and bacteriological properties of the drinking water supplied meet the requirements of the Drinking Water Ordinance at all times . The very soft (lime-free) and chemically corrosion-resistant water has a hardness range between 1 and 2 (7 ° dH). The difference between the supply areas, which results from the supply of the Bonn valley zone with a higher proportion of groundwater treated in the Untere Sieg waterworks, is only slight.
Utilities
In addition to the groundwater wells, the dam and the two treatment plants, the Wahnbachtalsperrenverband has 230 km of transport pipelines (raw and drinking water). In addition, there are 16 drinking water tanks with a capacity of 113,000 m³, 17 pumping stations to increase pressure and a culvert to supply the part of the Rhein-Sieg district west of the Rhine and the federal city of Bonn. For reasons of redundancy , the culvert consists of two separate water pipes and was laid around 1.20 m below the natural bed of the Rhine together with two gas pipes to reduce costs.
Coverage area
- Federal city of Bonn
- municipality Alfter
- Eitorf municipality
- Municipality Neunkirchen-Seelscheid
- municipality Ruppichteroth
- Municipality Wachtberg
- Community Windeck (partial)
- District town of Siegburg
- City of Bad Neuenahr-Ahrweiler
- City of Bornheim (partially)
- City of Hennef
- City of Koenigswinter
- City of Lohmar
- City of Meckenheim
- City of Niederkassel (partially)
- City of Remagen
- City of Rheinbach
- City of Sankt Augustin
- Zweckverband Eifel-Ahr
Others
- All buildings that were in the area of today's reservoir and would have been flooded were demolished during the construction of the dam. However, there are still a few bridges within the reservoir that dry out when the water level is low (as was the case last in summer 2008).
- Some supply lines run through the reservoir, which were installed on the bed of the original Wahnbachtalstrasse and serve to supply the phosphorus elimination system.
- Since the dam serves exclusively to supply drinking water, its use for local recreation is limited, as swimming in the lake and camping in the protection zone, unlike in the case of reservoirs with mixed use (such as the Rursee , for example ), are prohibited and the offense can be fined up to 50,000 €. Even stepping on the dry sole during z. B. emptying of the storage space due to maintenance is not permitted without the corresponding permit. In addition, the area is difficult to see from the outside and difficult to access for rescue workers, so that in the event of an accident or a medical emergency there is a risk to the life of the unauthorized visitor.
- Angling is permitted in the Wahnbachtalsperre in accordance with the legal requirements for holders of a special, limited number of annual fishing permits. The most successful angler so far has been Franz Schmitz, who hooked an 18 pound trout in 1990. Every week a fisherman fishes off little bruises using a net in order to maintain the biological balance.
- In April 2008 it was announced that the asphalt concrete waterproofing of the dam needs to be renovated. For this purpose, the storage capacity was reduced by 35 million m³ by the end of June 2008, which led to large parts of the reservoir falling dry. Remnants of the old settlement were also temporarily visible.
- The names of the places on the reservoir often end in -lap .
Renovation of the main dam in 2008
In 2008, the asphalt sealing of the main dam had to be renewed above about 20 meters above the valley floor. For this purpose, the water level of the main reservoir was lowered by approx. 25 m, whereby large parts of the otherwise flooded Wahnbach valley fell dry. The main embankment including the forecourt was closed to visitors during the work. A vantage point has been set up for visitors on both sides of the dam, from which one has a good view of the renovation work. Unfortunately, these points were sometimes difficult to find for non-residents, which led many visitors to enter the construction site themselves. During the main phase of the work, a viewing platform was set up in the garden of the dam supervision in the northwest. The forecourt on the main dam has been accessible since mid-December 2008, and the dam itself has been accessible again since the beginning of July 2009. Since then, the platform on the southwest side has been partially accessible and partially (like the dam itself) cordoned off as a construction site. Neither temporary lookout point could be used for wheelchair users, the north-western one because there were stairs to climb there, the south-eastern one because the path, which initially consists of good forest paths, becomes steep and impassable at the end. However, the now accessible dam can be used by wheelchair users.
The re-damming began in mid-November 2008, shortly after the work on the main dam was completed. The regular water level was initially expected for March or April 2009. However, due to low rainfall, it was only reached in summer 2009, and water has been regularly withdrawn from the reservoir since mid-July 2009.
Supply lines through the reservoir (autumn 2006)
Bridge of the old Wahnbachtalstraße shortly before the fore basin, normally flooded (summer 2008)
View of the partially emptied reservoir with an exposed extraction tower (summer 2008)
The Derenbach Bridge (summer 2008)
Old road with sign in the emptied reservoir (summer 2008)
The Derenbach Bridge from a different angle (summer 2008)
Derenbachtalbrücke
View from the Hemmersch Röcken (summer 2008)
Bridge on the Hemmersch Röcken (summer 2008)
The 51 year old tree stumps (summer 2008)
Panorama, view from Pinner Berg (summer 2008)
Rehabilitation of the asphalt sealing of the main dam (summer 2008)
See also
swell
- ↑ Schweitzer, Hans-Joachim, The oldest plant communities in Germany, Geological history in the Rhineland: Fossils and rocks, 1994, Wighart v. Koenigswald and Wilhelm Meyer (eds.), Verlag Dr Friedrich Pfeil
- ↑ Bußgeldkatalog environment. In: Applicable decrees (SMBl. NRW.). Ministry of the Interior and Municipalities of North Rhine-Westphalia, February 4, 2017, accessed on February 9, 2017 .
- ↑ Wahnbachtalsperre Water Protection Area Ordinance. (PDF; 135 kB) Cologne District - The District President as the upper water authority, May 14, 1993, accessed on February 9, 2017 .
- ↑ Axel Vogel: Wanderer collapsed: Rescue mission in the Wahnbach dam. In: General-Anzeiger (Bonn). August 2, 2008, accessed February 9, 2017 .
- ↑ Stefan Villinger: Hegefischer Netz out for good drinking water - Blaufelchen in the Wahnbachtalsperre. In: Rhein-Sieg-Rundschau. P. 23 , accessed on August 8, 2017 .
- ↑ Axel Vogel: Memory emerges in the Wahnbachtal. In: General-Anzeiger (Bonn). June 19, 2008. Retrieved February 9, 2017 .
- ↑ Axel Vogel: Many people made pilgrimages to the Wahnbachtalsperre. In: General-Anzeiger (Bonn). December 6, 2008, accessed February 9, 2017 .
- ↑ 800,000 consumers receive drinking water as they did before the dam renovation. ( Memento from October 25, 2010 in the Internet Archive ) Wahnbachtalsperrenverband, July 15, 2009 .
literature
- various annual reports of the WTV
- Norbert Eckschlag, Wolfram Such: Water. 50 years of the Wahnbachtalsperrenverband. 1953-2003. Published by the Wahnbachtalsperrenverband. Edition Blattwelt, Niederhofen 2003, ISBN 3-936256-03-9 .
- Norbert Eckschlag: The new drinking water treatment plant of the Wahnbachtalsperrenverband. The structural concept. In: Management and protection of drinking water reservoirs. Quality and preparation of dams (= working group drinking water dams . ATT series 3). Lectures and discussions at the technical-scientific symposium on the 30th anniversary of ATT, on November 30, 2000. Oldenbourg-Industrieverlag, Munich 2001, ISBN 3-486-26512-1 , pp. 343–352.
Web links
- Website of the Wahnbachtalsperrenverband
- Dams directory NRW (PDF file; 122 kB)
- Dams in North Rhine-Westphalia; State Environment Agency NRW (PDF file; 121 kB)