Daring construction of the channels

Today, the feat of hanging wooden troughs – weighing several hundred kilogrammes each – from almost vertical rock faces
seems almost unbelievable. The water conduits were made from evenly thick larch trunks. Using a rope-like mesh of willow and birch branches attached to the front of the section, two of the bravest men – usually unmarried and always at risk of falling – guided the trough, which was lowered on ropes from above by strong arms, into the wooden structure made of thick beams previously hammered into the rock. It had to be ensured that the gradient of the water conduit was not less than 0.5m per kilometre, and on level stretches around 1 to 1.5m per kilometre. This is the only way to ensure an even flow over the entire distance. Even today, traditional bisses are often renovated and built without a single metal nail. However, modern solutions are also used to minimise water loss. For example, interlocking wooden channel sections are sealed with silicone, and watertight rendering is applied to the neuralgic points of channels that have been bricked or chiselled into the rock. Everyone who contributed to the construction and maintenance of the irrigation channels, or was able to pay for their share, was entitled to the water. Each person was allotted water rights: a Tessel (a small wooden board) was used to record how much (or how long) water could be drawn and when. One whole notch equalled one hour of water consumption. In the old days, the poor were only allowed to get their share of water at night, but fortunately that is now a thing of the past. The basic social principle seen here remains valid to this day – prosperity is secured through collective labour. The water supply from the bisses and their maintenance is still precisely organised in ‘water communities’ to the present day. What could be more satisfying than knowing that your grandfather built the bisse, your mother watered the vegetables or your brother recently calculated the optimum route with a 3D program?Just how highly water is valued in Valais, considered irreplaceable and often even ‘sacred’, can be gauged from the depiction of the Bisse d’Ayent on the current 100-franc note.


It’s true, nowhere else in Switzerland is the climate as dry as in Valais. Nowhere else, except in Ticino, are such high temperatures measured. Nowhere else does it rain so little, and nowhere else is the wind such a frequent guest as in the Rhone Valley. The characteristic topography has a direct impact onthe climate in Valais: as a large valley that divides the Alps into the Northern and Southern Alps, it is surrounded by high mountains on both sides. As clouds approach, they accumulate and empty themselves on these mountains before they even reach the Rhone valley. Clouds formed by evaporation in the valley itself rise and pour rain down onto high, uninhabited altitudes.In the driest areas of Valais, it rains far less than 600 mm peryear. This means that there’s more evaporation than precipitation!


In Ausserberg, on the south-facing slope above Visp, water from the catchment area of the Bietsch Glacier and the Wiwannihorn is collected in an aqueduct. A 35-kilometre-long bisse carries the water until it flows into countless fine branches. They run through the cultivated land like arteries, supplying water from high altitudes to the populated areas further down.The history of the Süe (the German dialect word for bisses) dates back to the Middle Ages (around 1378). The often dangerous construction process and complex maintenance challenges were the price paid to ensure the community’s survival.


Only if enough hay could be harvested in summer would the cattle survive the winter, and with them the people. Water has always meant fertile soils, food and life; drought, on the other hand, means poverty and migration.



Discovery tours along the bisses

You can’t fail to succumb to the charm of the Valais on
a hike alongside a bisse, as the irrigation channels
are calledin the French-speaking Lower Valais.
Whether adventurous, family-friendly or romantic
– variety is guaranteed on the historical trails.




Stunning four-thousand-metre peaks, sunshine and
perpetual snow – that’s the Valais we know and love.
Here, wherethe Rhone flows, where glaciers feed count-
less streams, why would anyone saywater is scarce?
Well, the bisses are proof that this has been the case
since the Middle Ages. They supply remote meadows,
fields, vineyards and orchards with precious water.