The great unknown

Although at least 80% of drinking water comes from groundwater (see Water Use and Consumption), the renewal of this resource is not well understood. An unknown portion of the effluent from the water balance feeds the groundwater, while the same amount of groundwater feeds back into watercourses (the total water balance doesn’t change). It is assumed (Sinreich et al. 2012) that only about 10% of the theoretically usable groundwater in Swiss reservoirs can be sustainably replaced (equivalent to about a third of the annual rainfall, or 18 km3). The natural replacement of the groundwater depends on the aquifer type (see Glossary). Water can linger for a long time in different aquifers. This time is determined by the underlying geology (how well can the (rain)water seep into the aquifer?), by the size of the groundwater resources, and by the presence of watercourses. The residence time of groundwater can be between a few months (along rivers such as the Aare) to over 10 years (limestone areas like those found in parts of the Alps and Jura mountains). In the case of heavy precipitation in karst areas, the rivers react quickly, although the majority of the water flows away underground before emerging at a source. Thus, all groundwater is not well mixed. Imagine a wet sponge: if more water is introduced, some of the water already in the sponge is pressed out.

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BAFU: Umwelt und Gesundheit in der Schweiz
  • 2019

Umwelt und Gesundheit in der Schweiz

Die Beseitigung von Schadstoffquellen und der Schutz natürlicher Lebensräume sowie der Arten- und Pflanzenvielfalt nützen nicht nur der Umwelt, sondern auch der menschlichen Gesundheit. Ein von den Bundesämtern für Umwelt (BAFU) und Gesundheit (BAG) gemeinsam herausgegebener Bericht zeigt auf, wie sich Umwelt und Gesundheit auf vielfältige Weise gegenseitig beeinflussen, welche Fortschritte im Umweltschutz unserer Gesundheit zugutekommen und wo Handlungsbedarf besteht.