Drought refers to exceptional, climatologically unusually dry conditions that pose a challenge for the authorities, sectors and ultimately the general public. They are not to be equated with dry periods that are climatologically usual for a season or a particular region.
As for other natural hazards, official warnings are issued so that affected authorities and sectors can prepare for an impending drought in good time. These warnings, issued per region, are based on the weekly expert assessment of the current situation and the combined drought index forecast (CDI). They differ from the automatically calculated CDI in that they interpret trends and take into account forecast uncertainty.
The drought hazard levels issued for each region are explained below. They are based on the hazard levels specified in the Civil Protection Ordinance (Art. 24) (german).
Little to no risk of a prolonged drought lasting several weeks. Nonetheless, annual or local water-saving measures may be in effect.
No specific guidance necessary.
The combined drought index shows no significant deviation from the long-term average for several variables (precipitation, discharge and soil moisture) in the coming weeks.
A prolonged drought lasting several weeks is anticipated. Local or regional restrictions on water use, such as water abstraction bans, may be introduced. The risk of forest fires may be elevated. Further information available at Drought and impacts – National drought platform.
The combined drought index shows a noticeable deviation from the long-term average for several variables (precipitation, discharge and soil moisture) in the coming weeks.
Drought warnings only issued for hazard levels 2 and 4. Hazard level 3 is not used for drought situations as it would not make any noticeable difference to the general public compared to level 2.
A significant increase in drought conditions is expected. Local or regional restrictions on water use are likely, e.g. shutting off fountains, hosepipe ban for watering gardens or washing cars. The risk of forest fires may be seriously elevated. Further information available at Drought and impacts – National drought platform.
The combined drought index shows an extreme and unusual deviation from the long-term average for several variables (precipitation, discharge and soil moisture) in the coming weeks.
Drought warnings only issued for hazard levels 2 and 4. Hazard level 5 is not used for drought situations as it would not make any noticeable difference to the general public compared to level 4.