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Drought is when there is a water shortage over a long period of time due to insufficient rainfall or high evaporation. A distinction is made between meteorological, hydrological and agricultural drought.


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In meteorological drought, there is a lack of precipitation over a long period of time. Hydrological drought occurs when the water levels in lakes and rivers fall below a certain level due to precipitation deficits in their catchment area. Agricultural drought occurs when plant roots receive too little water, for example because the groundwater level drops. Different ecosystems and economic sectors are affected depending on the duration of the drought.

Various climate indices for drought

Depending on the definition, different climate indices are used to describe drought. For example, meteorological drought is measured by the maximum number of consecutive dry days. This index is defined as the longest period in a year during which less than 1 mm of precipitation is measured on consecutive days at a weather station.

Of all the weather stations monitored by MeteoSwiss, only Genève-Cointrin exhibits a trend towards longer phases of consecutive dry days during the period from 1961 to the present. According to the VH2018 Climate Change Scenarios, longer dry periods in summer are to be expected in the future.