Vranovská přehrada
| Vranovská přehrada | |||||||
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| Coordinates | 48 ° 54 '22 " N , 15 ° 49' 10" E | ||||||
| Data on the structure | |||||||
| Lock type: | Gravity dam | ||||||
| Construction time: | 1930-1934 | ||||||
| Height above valley floor: | 54 m | ||||||
| Height above foundation level : | 59.87 m | ||||||
| Building volume: | 220,000 m³ | ||||||
| Crown length: | 296 m | ||||||
| Crown width: | 7 m | ||||||
| Base width: | 41 m | ||||||
| Data on the reservoir | |||||||
| Reservoir length | 30 km | ||||||
| Total storage space : | 133,000,000 m³ | ||||||
| Catchment area | 2,214 km² | ||||||
The Vranovská přehrada ( German dam Frain) is a dam built between 1930 and 1934 with the associated reservoir on the Thaya in the Czech Republic . It is located near Vranov nad Dyjí in South Moravia near the Austrian border.
Occasions for establishment
The Thaya is a river with large fluctuations in the water flow. During the snowmelt in spring or after heavy rainfall, it carries large amounts of water, but in summer there is low water. And both had partially negative effects for the communities on the Thaya.
With advancing electrification, the demand for electricity increased and this was to be met by hydropower.
The Thayatal Railway to Raabs an der Thaya was planned from Znaim an der Thaya / Znojmo nad Dyjí . The dam's electricity would have been used for their electrical operation.
First power plant planning
The wood sculptor Roman Loos from Znojmo an der Thaya presented initial ideas about building a power station on the Thaya. His early death in 1890, however, put an end to the planning.
Other plans included a dam between Vöttau ( Bítov ) and Freistein an der Thaya and a tunnel to a power house in Frain an der Thaya . However, the slight gradient did not allow economical operation.
Although there was still no concrete project, agreements on water rights were already in place around 1900 .
The engineer Ferdinand Schmidt from Frain combined the above-mentioned problems and wishes and found the solution in the planning of a large storage facility, which originally consisted of three dams. But in the course of his geological and hydrological investigations it soon became apparent that the construction of a single large dam wall above Frain an der Thaya was the best solution.
His plans stipulated that the dam should absorb tidal waves in the storage space that was kept free and release it evenly to the lower reaches of the Thaya, so that the communities below the dam always had an even amount of water available even in dry periods.
In addition to his technical investigations, he also began to take care of the future financing of the project. The state, the states of Moravia and Lower Austria and private financiers such as the “Schweizer Bankverein” should work together as donors .
After official commissioning in 1912, the “Thayatalwerke für Stau- und Elektrizitätsanlagen company with limited liability” received the building permit, which became valid after objections in 1914 and was limited to ten years.
The project came to a standstill due to the First World War and the subsequent uncertainties caused by the establishment of the Czechoslovak state.
Interwar period
Schmidt was not deterred. He kept collecting technical data and reuniting a funding group. However, time was starting to run out. The newly established Czech state renewed the concession in 1919, but only for three years.
The loss of the concession would have been a personal catastrophe for him, because he had financed a large part of the building preparations out of pocket.
In 1921, the West Moravian Electricity Company appeared unexpectedly to negotiate with him about the purchase of the concession project that was ready to build. With the impending total loss of the financial resources he had in mind, he had no choice but to agree to the low purchase price. As a visual improvement, he was offered the top management of construction as a well-paid employment contract. In addition, he was granted the exclusive rights to shipping and fishing for further marketing. The contract was signed on April 25, 1921.
Despite the crude negotiating methods with which he had been put under pressure, Schmidt continued to fight for the construction of the dam.
The construction
Although the construction project was planned to be ready for construction, the start of construction was repeatedly delayed. It was not until February 1929 that the Brno State Office put the construction of the Frain dam on the Thaya out to tender.
The end of October of the same year was the Minister of Public Works - Franz Spina - the result is known: The contract was awarded, the consortium Bohemian-Moravian construction company shares ( Prague ) - Lanna Aktiengesellschaft (Prague) - Pittel + Brausewetter (Brno).
In the last months of 1929 the necessary preparatory work began (workshop, residential and office buildings, temporary bridges and tracks for the material railway). The concrete mixing plant as well as the ballast crushing and sorting plant, which were supposed to process the building material obtained on site, were built where the numerous small restaurants stand today.
On January 8, 1930, the material railway, built as a narrow-gauge railway, was picked from the construction site to the Schönwald train station ( Šumná , Nordwestbahn Wien – Prague), where a separate material transfer station had been built.
The foundation stone for the dam was laid on April 1, 1930, without any major celebrations, in the presence of the new Minister for Public Works, Dostalek.
In the first construction phase, the Thaya was moved to the right bank in order to be able to build the half of the wall with the four bottom outlets and the stilling basin on the left bank . At the same time the cascades of the water overflow were built.
The dam wall was built from cast concrete ("plastic concrete"). This was produced in the electrically operated concrete mixing plant, filled into containers and transported by cable car to the respective construction section and filled into the formwork using cast channels. This plant had a daily output of 1,200 m³ concrete per day.
During the construction of the construction section on the right bank, the Thaya was diverted through the openings in the bottom outlet. In the event of a flood, a construction section was left a little lower to support the bottom drain.
After the actual dam was completed, the road with two sidewalks was built over the dam and the power plant center was expanded.
The electrical equipment
Schmidt's plans included 10 Francis turbines in five groups - graduated from 3200 HP to 960 HP per turbine - in order to achieve the best possible equalization of water level and electricity demand and to allow the most uniform amount of water to pass through the dam. In addition, the water supply to the turbines was designed so that as much warm surface water as possible should drive the turbines in order not to cool the river below unnecessarily.
Not much was left of these considerations in the final construction. In the end, only two Francis turbines were used, the water was cold deep water. The third turbine was not installed until 1938.
Transporting the two Francis turbines and the other mechanical equipment for the power station posed major problems for the engineers, because neither the motor vehicles nor the local roads of the time met the requirements. So often several tow vehicles had to be harnessed together in order to move on often not even asphalted paths.
In 1934 the power station building, located directly on the dam wall on the right bank, was completed and the expansion of the high-voltage line to the Oslawan thermal power station near Brno, which had previously supplied the concrete mixing plant with the required electricity, began. This line was not completed until 1936 and was the first 100,000 volt high-voltage line in West and South Moravia.
Completion and full jam
In 1933 the traffic jam started unplanned. The spring thaw and heavy rains filled the reservoir, so that a water height of 15 meters could be measured at the dam. This water level was sufficient to partially flood a mill above the dam and the residents of the village of Vöttau (Bítov) realized that it was no longer possible to stay in "Alt-Vöttau" and it was high time to move to the newly built "Neu-Vöttau". The names "Alt- und Neu-Vöttau" were not official.
Since the dam was not yet fully resilient at this point in time, the bottom drains were opened. It also became apparent that the necessary clearing work in the damming area had not been carried out thoroughly enough and that this, together with drowned game, ensured that the pent-up water turned into a putrid and smelly liquid.
The dammed water had to be drained and then the damming started again. It took until 1935 before the full jam was reached. In May 1935, the Znojmo newspaper called on its readers not to miss the interesting spectacle of the overflowing water.
On April 11, 1934, power generation with two turbines began, and the dismantling of all ancillary facilities required for the construction and the recultivation of the construction site began.
In 2004 and 2005, the now 70-year-old power plant was renovated.
process
The total costs for the construction of the dam were around 132 million crowns, a lot more than had been planned. This fact, coupled with rapidly emerging rumors of financial irregularities and bribes, could only have one result.
On December 9, 1935, the trial began before the Brno Criminal Senate. In addition to the head of the construction administration during the construction of the dam, there were charges against the executing construction companies as well as some supplier companies. One of the charges was the "crime of inducement to abuse official authority".
The verdict was pronounced on December 21st. The head of the building administration dealt with the heaviest punishment when the dam was built: one and a half years heavier dungeon that was tightened every month by a fast day. Two other defendants were imprisoned for 10 months on one fast day a month. In addition, all of the defendants had to reimburse the legal costs and lost the right to vote in municipal elections for three years.
Aftermath
During the construction of the Frainer Dam, some changes were made to the planning originally carried out by Ferdinand Schmidt or the requirement to drain a certain minimum amount of water during dry periods was not complied with. The fact that the construction management only applied for approval of the changes after a fait accompli had been created, led to massive protests by the affected communities.
The city of Znojmo complained that the power plant did not serve to regulate the water balance of the Thaya as planned, but only to generate electricity. In addition, it must be ensured that not so much cold water is drained off, as this would massively damage the bathing industry in the Thaya (Schmidt's plans had taken care of this!).
Frain an der Thaya also presented a long list of deficiencies regarding the construction and operational management of the dam.
Corresponding entries were unsuccessful. On February 20, 1936, the negotiation of the water permit took place in Znojmo.
Again, the arguments of the affected communities were put forward. The reaction of the delegation from Hardegg (Lower Austria) was most energetic . She protested against being fobbed off with any excuses.
The negotiation was unsuccessful for the affected communities.
Today the two national parks Thayatal and Podyjí still complain about the surge of water that is generated by the generation of electricity, as this affects the life of the animals in the river and in the immediate bank area.
Tourism at the dam
Frain an der Thaya had been a popular place for summer holidays even before the dam was built. But now tourism has taken on a new dimension: excursion boats for tours on the reservoir have been purchased. After South Moravia had also become part of the 3rd Reich, a town partnership with Starnberg was established and one of the motor boats there was transported to Frain.
Tourism ceased during the war, and the population of German origin was expelled on May 24, 1945.
After the war, tourism picked up again, and boats went back to Vöttau Castle . The Iron Curtain prevented vacation travel to the south, so the bank of the reservoir had to replace the Riviera. Campsites and holiday homes emerged.
Since the reservoir serves as a drinking water reservoir for numerous communities on the Thaya (such as Hardegg in Austria or Znojmo in the Czech Republic), it was declared a water protection area in the wake of the Velvet Revolution and the traffic of excursion boats has been suspended, but is now back in operation .
The dam and the war
As a result of the bombing of the Möhne Reservoir in 1943, the population feared that this could happen again here as well. The civilian population of Frain an der Thaya was therefore instructed to deposit clothes and documents with relatives and acquaintances outside the Thaya valley in the event of a disaster.
Calculations showed that if the dam was completely destroyed, even the relatively distant Lundenburg ( Břeclav ) was still endangered by the tidal wave. As a precaution, a "Neu-Lundenburg" was therefore planned on a higher site.
But apart from an anti-aircraft battery with quadruple guns on the dam wall, no defensive measures were taken. In addition, a steel cable was stretched between masts, which should prevent or make attacks more difficult. In addition, the navy mined parts of the reservoir.
Further power plant projects
A power plant at Baumöhl was considered as a follow-up project . However, the backlog of this lock would also have affected Austrian territory and therefore, based on existing agreements with the Republic of Austria , obliged to sell electricity at cost price. The project was not carried out.
The Niederdonau Gauwerke, which took over the management in 1938, planned a larger dam above Znaim an der Thaya and a smaller equalization basin above Hardegg. In 1943 the project would have been ready for construction, but the development of the Second World War prevented its implementation.
As early as 1945 there were technical talks between the West Moravian Electricity Works and the newly founded NEWAG in Lower Austria about the construction of the aforementioned equalization basin, since Austrian territory would also have been affected. However, the political developments in Czechoslovakia in 1948 ended these talks.
In 1966, the Austrian government took the initiative and wanted to support the project, which had failed in 1948, as part of the border region promotion. But the planned economy in Czechoslovakia prevented this. In addition, a small dam was built at Znojmo nad Dyjí to secure the city's water supply.
The last attempt to build a power plant in this region was once again the project near the Bull Rock above Znojmo nad Dyjí. But since Austrian territory was also affected, the negotiations dragged on. In the meantime, nature conservation began to take hold and instead of the power station, two national parks were created: The Thayatal National Park in Lower Austria and the Národní park Podyjí in South Moravia.
The Thayatalbahn
The Thayatalbahn project from Znaim an der Thaya to Raabs an der Thaya was one of the triggers for the construction of the Frainer dam due to the planned electrical operation and the electrical power required for it.
Ferdinand Schmidt was also heavily involved in this project, together with Heinrich Friedländer from Zurich . They made their first concrete proposal in 1904. Most of the route was to run in Moravian territory and only a short stretch in Lower Austria to Raabs.
The approval of this railway line was great, but when the project was ready for construction, the First World War began. After the end of the war and the establishment of the new Czech state, the latter declared that he was not interested in this railway line near the border.
The Thayatal Street
Thayatal Straße was a project from the interwar period . On the occasion of the tourism conference for the Thayatal in September 1929 in Waidhofen an der Thaya , the construction of a motor vehicle road through the Thayatal in South Moravia and Lower Austria was shot at. It should connect Znaim an der Thaya and Waidhofen an der Thaya and if possible follow the course of the Thaya in order to show the travelers the splendor of the Thaya valley.
Ferdinand Schmidt, who was busy with the planning of the Frainer dam, was asked to include the road section Frain - Freistein an der Thaya ( Podhradí nad Dyjí ) in his planning. But this project was not implemented either.
Ferdinand Schmidt
Ferdinand Schmidt was born on December 18, 1878 in Frain an der Thaya. In addition to his job as an engineer, he was mayor of Frain from 1923 to 1927. He was also director of the Frainer Sparkasse. In 1914, the city of Hardegg an der Thaya in Lower Austria made him an honorary citizen in gratitude for his efforts to build the “Thayatalbahn” . He died on September 27, 1941 in Frain, where he is also buried in the local cemetery.
His family, like all other German-speaking Frainers, was expelled in 1945.
On the 30th anniversary of his death (September 27, 1971), a memorial ceremony was held at his grave on the initiative of the South Moravian Energy Works n.p., Brno, with the full consent of the political authorities. His next of kin were invited and the visas were even made available.
In 1978, on the occasion of the hundredth birthday, a celebration was held in the presence of the mayor of Vranov nad Dyjí. The Schmidt family was not invited to this.
The grave has been an honorary grave since 2001.
Technical specifications
- 4 bottom discharge pipes of 160 cm each
- Water supply to the turbines: 3 pipes of 260 cm each
- Turbines: 3 Francis turbines à 5,400 kW
- Annual electricity generation: approx.25,000,000 kWh
literature
- Willy Anderle, Walter Schmidt: Frain - once the pearl in the Thayatal. Volumes I and II, self-published, 2002.
- Miroslav Vanék: Vranovska Přehrada - stavba - úzkokolejky - provoz - lodni doprava . Sursum Verlag, 2012, ISBN 978-80-7323-238-2 .