Obersauer reservoir
| Upper Sauer Reservoir Esch-Sauer Reservoir |
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| Coordinates | 49 ° 54 '42 " N , 5 ° 55' 22" E | ||||||||
| Data on the structure | |||||||||
| Lock type: | Arch dam | ||||||||
| Construction time: | 1955-1958 | ||||||||
| Height of the barrier structure : | 142 m | ||||||||
| Height above the river bed : | 43 m | ||||||||
| Crown width: | 1.5 m | ||||||||
| Base width: | 4.5 m | ||||||||
| Power plant output: | 15 MW | ||||||||
| Operator: | Syndicat des Eaux du Barrage d'Esch-sur-Sûre (SEBES) | ||||||||
| Data on the reservoir | |||||||||
| Water surface | 3.8 km² | ||||||||
| Storage space | 60 000 000 m³ | ||||||||
The Obersauer reservoir (also Esch-sur-Sûre dam ) is located near Esch-Sauer in Luxembourg and is the largest lake in the country. The Sauer , which rises in the Ardennes , and its numerous tributaries deliver 175 to 240 million cubic meters of water annually.
The project
When Luxembourg's natural drinking water reserves were no longer sufficient at the end of the 1940s, the Luxembourg government decided in the early 1950s to use surface water for drinking water production .
This required a clean, year-round flowing body of water, in the vicinity of which neither large cities nor industries were located. The problem of sufficient water reserves could only be solved by a dam , as there are no large natural lakes in Luxembourg. The narrow Sauer river valley and the rocky banks, which give the dam wall a good and firm hold, offer good conditions for creating an artificial lake.
The construction time for the 47 meter high arch dam was just under three years, from 1955 to 1958. The wall thickness varies between 1.5 meters at the crown and 4.5 meters at the foot of the wall.
When fully filled, the reservoir covers an area of 3.8 square kilometers and has a capacity of 60 million cubic meters of water. The lake is up to 43 meters deep.
In the valley there were several mills and farmsteads whose residents had to be relocated before the dam was built. Today divers can still visit the remains at these points at a depth of about 30 meters.
In order to keep the lake water as clean as possible, dams were built below Pont Misère and not far from the village of Bavigne with storage heights of 9.6 meters and 23 meters. There, driftwood , tree trunks and sand particles are caught before they can get into the lake.
The SEBES
SEBES stands for Syndicat des Eaux du Barrage d'Esch-sur-Sûre . The syndicate was launched in 1962. Members are the four syndicates SES, DEA, SIDERE and SEC, which are responsible for the nationwide water supply of the country, as well as the city of Luxembourg .
The tasks of the SEBES are the processing of raw water from the Upper Sure reservoir to drinking water and subsequent delivery to the distribution networks of the different communities. It was not until the SEBES systems were built in 1969 that the country's central water supply was possible. Thus (as of 2007) around 80 percent of the population in Luxembourg is supplied with SEBES water.
The emptying of the reservoir
The entire reservoir has only been emptied twice in its previous existence: the first time in 1965–1966 to enable the installation of a fixed raw water extraction line, the second time in 1991 for repair purposes and to set up a height-adjustable suction arm (see below) 140 meters from the dam .
The reservoir is only emptied in official agreement with the barrages in the valley in order to avoid flooding. When emptying the dam, the locks are opened a maximum of 15 centimeters. The air suction that occurs at the lock opening is enormous. Workers have to rope up there to avoid being carried away. The whole process then takes about four weeks. Refilling takes about three months depending on the time of year and the amount of rainfall. The lake is not completely emptied, it shrinks back to the original river size, which looks like a trickle compared to a full lake. The fish that swim in the lake must be caught by hand and kept in an artificial tank near the SEBES halls for the duration of the emptying.
Many items came to light during the 1991 emptying, including some boats, bicycles and a large amount of discarded household appliances. The next complete emptying of the reservoir is planned for 2023 at the earliest.
The height-adjustable suction arm
The height-adjustable 16 meter long suction arm in the Esch-Sauer reservoir was a child of necessity. When the reservoir's algae plague increased rapidly in the 1980s, a decision had to be made. The permanently installed raw water extraction line at the foot of the 47-meter-deep dam wall increasingly sucked in more and more algae. So they decided on a completely new construction:
A 22-meter-high, height-adjustable suction arm that can pump raw water out of the cleanest layer of the reservoir in different seasons. During the emptying in 1991, it was installed at a distance of about 140 meters from the dam.
There the raw water is taken from water protection zone 1. The suction arm sits on a frame, which is anchored in the ground with four concrete blocks . Stainless steel was used as the building material for the frame and the suction arm . When viewed from a distance, the construction called the extraction device has a certain resemblance to an oil rig .
The water is pumped into a raw water tank with the help of centrifugal pumps , which has a capacity of around 5000 cubic meters. The container is at the highest point of the treatment system, so the water flows through all the other stations of the system automatically thanks to gravity .
The diameter of the suction arm is 70 centimeters; the conveying capacity is 1200 liters per second.
Hydroelectric power plant
The high pressure of the water is used to generate electricity. Two Francis turbines, each with an output of around 5500 kilowatts, were installed in the two lower bulkheads of the dam . On the section of the river below the dam wall, three weirs and a compensation weir are distributed over a length of four and a half kilometers . These contain a total of seven Kaplan turbines with a total output of 1850 kilowatts.
The operator of the plant is the joint stock company SOLER, half of which is owned by the energy supplier Enovos and the power plant company Société Électrique de l'Our , and which is also responsible for the hydropower plants in Ettelbrück and Rosport .
See also
Web links
- Barrage Esch-sur-Sûre on the website of the Luxembourg Road and Bridge Administration (French, partly German)
- official website of SEBES
- Esch-Sauer run-of-river power plant on the Société Électrique de l'Our website
Individual evidence
- ↑ See also this diving map on a French leisure portal. PDF file, 503kB, accessed July 2, 2013.
- ↑ Information about SOLER on the website of the Société Électrique de l'Our, accessed on July 2, 2013.