Dlouhá stoka (Long Ditch) is a technical monument of major significance intersecting a large part of Slavkovský les (Slavkov Forest). The water canal was completed in 1536 because mining was consuming more and more water for driving mining machinery and equipment and also the supplies of wood in the surroundings of Horní Slavkov and Krásna were thinning, and it was necessary to transport wood to the mining areas from the distant Kynžvart forests. The route was staked out by mine surveyor Rossmeisel and the waterworks were named Flossgraben. It represented a highly purposeful and elaborate project interfering with the natural water regime. Taking into consideration the terrain configuration, the project mainly required due management of all surveying activities and maintaining a minimum decline that would guarantee the successful transport of water to adequate elevations and thereby secure the success of the overall project. Apart from digging and paving, a major part of the work involved building relatively large-scale and watertight dams and dikes on the slopes.
The total length of the water ditch was 24.2 km.
The Flossgraben water ditch largely copied the route of the original older ditch. It lead from the Róta River and on its way, it absorbed excess water flowing from the Kynžvartský rybník (Kynžvart Pond). Almost copying the contour line, it supplied water up to Teilhäsel where it split into two branches. One branch continued to Seifertsgrün, apparently following the same route as the older ditch dating to 1499. The second branch headed towards Krásno. Water was partially diverted to a number of mining ponds and subsequently to mining and mineral processing plants. The average width of the water ditch was 2 metres and its sides were undoubtedly lined with logs to facilitate transport of timber. The bed was of a trapezoid shape with a width ranging from 1.2 to 3 metres. The average depth was about 1 metre. Segments passing through the towns of Krásno and Horní Slavkov were laid with bricks.
The water flow was quite rapid and the difference in elevation between the beginning of the ditch (810 metres above the sea level) and its confluence with Slavkovský potok (Slavkov Brook) in Horní Slavkov (587 metres above the sea level), i.e. along a distance of 24.2 kilometres, amounted to 223 metres. The decline on a 100-metre segment ranged from 0.35 to 0.83 metres and the flow rate was approximately 0.4 m3/s. The last construction work involving the building of concrete bridges across the water ditch, as well as other repair and reconstruction work was completed in 1908. Later, the bed was narrowed by partial filling. The worst times for this once one of the most remarkable water mining works in Europe, built in the 16th century, began after World War II.
The devastation of the landscape along with the mining activities of the Jáchymovské doly n.p. (Jáchymov Mines, national enterprise) resulted in the damaging and partial destruction of the waterworks, especially of some parts of the canals, drainage adits, and mining ponds. Due to intense mining of tin and wolfram ore by the Rudné doly s.p. Příbram (Ore Mines Příbram, state enterprise), a part of the Flossgraben was re-routed through a new concrete-bed route. The hectic period of privatisation in the early 1990s gave another blow to the unique waterworks with its uncontrolled construction of small water power plants. Moreover, agriculture known for its little concern for historical values, also did not contribute much to the preservation of the Long Ditch.
Fortunately, the present situation is better. Thanks to the efforts of local people, natives, and the Georgius Agricola Foundation for the region of the Slavkov Forest; the entire water route is fully functional and the original technical road, formerly used for maintenance purposes, has been renewed around some of its length. In September 2003, the Ministry of Culture included Dlouhá stoka on the list of cultural monuments.
The information retrieved from the Slavkov Forest website has been used with the kind permission of Daniel Šťastný.