Groundwater
During a dry period lasting several weeks, there is a lot less precipitation than usual, so less groundwater is formed. Groundwater resources that are mainly fed by precipitation are therefore more sensitive to dry periods than groundwater resources that are also fed by river or lake water. However, during longer dry periods rivers carry little or no water, so are also unable to replenish groundwater to their usual extent.
The degree to which drought affects groundwater volume also depends on the nature of the subsoil, the thickness of the groundwater and the depth at which it is situated. Because of the complex subsurface properties and the small-scale topography of Switzerland, there are considerable local and temporal differences in the impact of drought on groundwater resources.
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