The foremost part of the Vispertal valley is the driest region in Switzerland. At the measuring point Ackersand below Törbel, the average annual precipitation is 520 litres per square metre. The high mountains all around force the clouds to dump their moisture onto the peaks and passes – and the Valais valley floor usually ends up empty. By comparison, just under forty kilometres from Ackersand – in Mönchsjoch – more than 3,500 litres of precipitation are measured annually. This means the parts of the Valais valleys that cannot be irrigated are unable to be used for agriculture. And since the sunny terraces are not to be found on the valley floors, but on the balconies outside, the people of Valais have had to ‘fetch’ the water in the narrow, steep valleys at the end of the glaciers ever since they cleared and settled in the long Rhone valley. The oldest water pipe in Valais was discovered a few years ago in an archaeological dig during motorway construction in the Pfynwald forest. It dates back to Roman times.
The lack of precipitation is accompanied by constant winds which dry out the ground. From mid-April to September, meadows, vines and fields must therefore be irrigated in order to harvest anything at all. In perilously balanced wooden ‘gutters’, medieval builders overcame vertical rock faces with the gentlest possible incline, to avoid losing any water. It was not unusual for men to fall to their deaths. In this way, they atoned for misdeeds committed in the village – inspiring the name ‘Suon’, which comes from the German ‘Sühne’, or ‘atonement’. Over the centuries, an extensive network of thousands of kilometres developed across the whole of Valais, branching out from the tributaries via the ‘Suons’ into increasingly narrow waterways reaching every piece of cultivated land.