Comparison between the current border (pink line) and the 1940 border, shown here on the national map published in 1967 (black crosses)

The water divides above 3'500 metres have shifted over the course of time, partly due to melting glaciers.

Such a case occurred on the border between Switzerland and Italy at the Furggsattel above Zermatt: the border was aligned with the retreat of the glacier of  Theodule in 2000. As a result, the chairlift station has since then been located on Swiss territory and not in Italy.

The graphic representation illustrates how the courses of borders in the Zermatt region are influenced by melting glaciers. From 1940 to 2000, the height of the glacier has decreased and the water divide now follows the rocks. This decrease causes a shift in the border by 100 to 150 metres.

Only approx. 40 kilometres of the water divides between Switzerland and Italy (total length 578 kilometres) traverse snow fields or glaciers. There are no snow fields or glaciers along the other alpine borders between Switzerland and France and Switzerland and Austria which could result in any positional changes. In these regions the entire border runs along solid terrain. However, it cannot be ruled out that this type of border may also change, for example during a major rockfall.

As the federal authority responsible for the national border, swisstopo has to take these positional changes into account in order to accurately update various surveying, topographic and cartographic products. However, updates are only carried out as the need arises (for example, when the boundary change affects a construction).

The border between the canton of Geneva and France has a total length of 103 kilometres, 50 of which pass through the middle of rivers. Over time, and as the result of flooding, these rivers have changed their course. Surveys show that in various places the borders have shifted by several metres.

The same situation applies to the Doubs River, which forms the border between France and the cantons of Neuchâtel and Jura. As long as these rivers are not contained within channels, the borders will follow their natural course. Here again, nature decides and we can only accept these natural changes. As with glaciers, the boundary is adjusted along rivers when there is a significant change.

Overlaying the current boundary (the pink line) on old maps reveals changes in alignment. Here are some examples: