The Dam and the Hydro-Power Plant on the Kwisa River near Leśna

The Kwisa river – a left-bank tributary of the Bóbr River, floating through the Izera Foothills accumulates water from an approximate area of 300 km2. This is an area cleared of trees due to a human activity. Often repeated floods, especially the catastrophic ones that occured late in the XIX century in 1888 and 1897, forced the authorities of the Silesia Province to build dams and reservoirs. Professor Otto Intze, from the Aachen University, worked out a safety system for the mountain rivers in the Sudety region. He was also an architect of the gravity dams made of rock and concrete mix. The first dam of this type in Silesia is the described construction built in the eye and fine-grained gneissic granites at the beginning of the Kwisa’s gorge just above Leśna. The engineering works were directed by doctor of engineering, Mr. Curt Bachmann who was also a builder of the dam in Pilchowice on the Bóbr river and several others. In the Autumn 1901 the earth and mining works started as a part of a water circulation adit’s drilling process under the left bank of the river. It enabled to heap up a cofferdam beneath which the fundaments of the dam had been hewn out. 32 tons of explosives were used in the mining blasting works. 450 workers from Austria and Italy were brought along. Six months later another water circulation adit under the right bank of the river was finished. The side sluices used for keeping a constant level of water were built in front of the abutments of the dam. 40 meters deep well sluices were hewed out just above the side sluices to keep up the flood-water flow (660 m3 per second). From the top they were covered with ornamental bars. The bottom and side sluices are connected to the water circulation adit. In the granite shelters near the culverts there are water gates that regulate the flow of the water in the water circulation adit if the reservoir needs to be emptied.The body works of the dam were completed on 15th July 1905. 600 carriages full of concrete, 20000 m3 of sand, 2400 m3 of lime, 460 tons of the reinforced steel and  rocks  from

the nearby stone-pit were used to build the dam. The concrete was prepared according to the special recipe which included tuff brought from the Rhineland. Thanks to the dam a 140 ha reservoir was created with a capacity of 15 million m3 including a flood reserve of 8 million m3. The barrier lake is t kilometers long, up to one kilometer wide and has a diversified coastline. Between 1905 and 1907 a power plant with three turbines of J.M. Voith design were built beneath the dam. In 1908 three turbo-units were added. The plant has a power of 2.61 MW and is the oldest power station in Poland. Water flows under the dam onto the turbines through the two bottom culverts. There are two water-gates in the dam. The additional water-gates were installed in the granite shelters at the bottom of the dam in case of any damage. The height of the dam is 45 meters, including 36 meters above the earth surface level. At the bottom it is 38 meters wide and 8 meters wide at the top which is decorated with the ornamental railings. The top of the dam is situated at 282 meters above the sea level. The capacity of the dam is 63000 m3.The Leśniańskie lake functions nowadays as a power engineering facility, reservoir and a recreational area including relaxation and water sports facilities. Just beside the Lake there is the impressive Czocha Castle build on the rocky promontory. On the opposite shore there is the romantic Rajsko Castle with a wharf just beneath it. There are bicycle lanes and hiking trails all around the lake leading to Gryfów Śląski, Leśna, Lubań and Świeradów Zdrój.
The dam and the power station can be reached by car and bus on route: Gryfów Śląski-Leśna-Lubań.

Information concerning the dam can be found on the website:
www.tauron-ekoenergia.pl

Edited by Antoni Witczak
Translation: Andrzej Rudkowski

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