The Alm canal: the historic waterway between the Königsseeache and Salzburg
Since the 12th century, the Alm canal – a masterpiece of historical hydraulic engineering – has supplied the town of Salzburg with water for drinking, industry and fire-fighting. Today, it forms an important recreational area, as well as serving to generate energy.
The oldest part of the Alm canal network, the Mülln arm, was probably built as early as the 9th century. Between 1137 and 1143, the major landowners, the Cathedral chapter and St Peter's Abbey approved the boring of the Stiftsarmstollen, 400m-long tunnel, through the Mönchsberg in order to connect with the large quantities of water in the Leopoldskron district. In the 13th century, the canal was extended as far as the Königsseeache.
Over the centuries, the Alm canal had many functions, such as supplying water, driving mills and, from 1892 until 1959, also the Fortress funicular railway. Today, the Alm canal provides water for 14 turbines, including the oldest electric power station in the Province of Salzburg, the municipal emergency generator, several ponds, and the refrigeration and air-conditioning systems in the Festival Halls, the Natural History Museum, Salzburg Museum and other buildings in the Old Town. The mill-wheel of St Peter's bakery is still driven by water from the Alm canal.
The Alm canal is increasing in importance as a recreational area. There is a surf-wave for the adventurous, paths from the Old Town along the canal for walkers and cyclists to reach the southern region of Salzburg, and places to bathe on hot summer days.
The exciting history of the tunnel system can be explored during three weeks every September, when the tunnel is drained for necessary maintenance work – locally referred to as "Almabkehr". The Königsseeache sluice is closed, and the water-level in the canal lowered to a minimum to allow a three-week period for cleaning and maintenance. Guided tours through the Stiftsarmstollen tunnel are offered during this period.
