However rich most of Switzerland is in water resources, the canton of Valais lacks its fair share. In order to bring scarce water to their fields, villagers built artificial water courses, called "bisses" in French and "Suonen" in German, running down from glacier melt water.

In the middle ages there were several thousand kilometres of channels in use, and even at the beginning of the 20th century the 200 or so remaining channels had a total length of about 2,000 km.

It was important to get the right speed of flow, and hence exactly the right slope for the bisses. If they were lucky, the builders were able to use natural channels, or simply cut ditches to direct the water; in the most extreme cases they risked their lives to drive struts into the sides of cliffs and then to lower specially constructed wooden channels onto them. It was not only the construction that was dangerous: the bisses also needed regular inspection and maintenance.