Switzerland makes predictions about avalanches, floods, and heat waves, but, unlike other countries, it doesn’t have a drought warning system – yet. What causes droughts, and how can they be predicted?
It is forbidden to water gardens, wash cars and fill swimming pools. Water is scarce and should be used sparingly. Otherwise, it could be rationed. This is what the residents of some Swiss municipalities were told in the summer of 2022, when Europe was hit by the worst drought in 500 yearsExternal link.
Some lakes, such as Lac de Brenets on the Swiss-French border, had nearly dried up. Low water in the Rhine River disrupted the shipping of goods imported into Switzerland. And army helicopters had to carry water over mountain pastures to reach thirsty livestock.
These lakes and rivers have now filled up, thanks to the rains in recent months. But the drought alarm is not over yet. Of concern is the scarcity of snow in the mountains, which could deprive Switzerland of an important source of water during the summer season, with serious consequences for water supply, agriculture, hydropower production and ecosystems.
No one knows whether and how much rain will fall this summer. There is no overview of the national water supply and demand, and unlike other countries, Switzerland has no early detection and warning system for periods of drought. This is set to change.
What is drought?
It is a prolonged lack of water due to insufficient rainfall or heavy evaporation. In 2022, Switzerland saw its lowest rainfall since local measurements began in 1864, according to the Federal Office of Meteorology and Climatology (MeteoSwiss). Between June and August, less than 40% of the expected rain fell in the country’s southernmost regions.
There are three types of drought. Meteorological drought is the absence of precipitation over a long period of time. In Switzerland, it is defined as the longest period in which less than one millimetre of precipitation is measured at a station. The record of 77 days was set in the city of Lugano in 1988; last year, the Coldrerio weather station, also in the country’s southernmost canton of Ticino, recorded the longest dry period with 40 days.
Hydrological drought occurs when the water level in lakes and rivers falls below a certain threshold. Last August, the levels of lakes Lugano, Lucerne, Constance and Walen reached an all-time low.
Agricultural drought occurs when the moisture content of the soil is particularly low and plant roots do not receive enough water – as was the case this spring in areas south of the Alps, according to MeteoSwiss. It is a very local phenomenon that depends on the type of crop and soil.
What causes drought?
The persistence of an atmospheric high-pressure zone that limits rainfall and high temperatures are among the main natural causes of drought. Increased drinking water consumption and water use, for example due to population growth, can also lead to a water deficit, while deforestation and intensive agriculture dry out soils.
Human-induced climate change is also causing droughts, or rather increasing their likelihood. The2022 summer droughts across the northern hemisphere were at least 20 times more likely to occur due to climate change, according to an international studyExternal link involving researchers from the Swiss Federal Institute of Technology in Zurich (ETH).
Why is it possible to predict most natural hazards in Switzerland, but not droughts?
Switzerland has been tracking and closely monitoring thunderstorms, wind, avalanches, floods, landslides, heat waves, and forest fires since 2014. Warning systems are activated if needed. The country also has a hail detection systemExternal link that combines data from weather radar and automatic sensors as well as reports from the public.
However, there is currently no warning system for droughts. The reason is simple: Switzerland has huge water reserves, and historically, drought has never been a concern.
How is Switzerland preparing for future droughts?
Despite its Alpine glaciers and countless lakes, rivers and streams, Switzerland is not immune to drought risks, especially when a dry winter is followed by a spring with low rainfall and an unusually hot summer.
From 1994 to 2017, the number of droughts caused by snowmelt deficit in the Alps increased by 15% compared to the period from 1970 to 1993, according to a recent studyExternal link by the Institute for Snow and Avalanche Research (SLF). “The trend will continue in the future,” says lead author Manuela Brunner.
In the long term, it will get warmer and drier in Switzerland. Periods of drought will become more frequent, more intense and last longer. In view of this outlook, the federal government decided last year to set up a national early detection and warning system by 2025. Early detection of droughts would, for example, enable farmers or operators of hydropower plants to better plan the irrigation of their land and electricity production, respectively.
What tools and technologies can predict a drought?
Currently, several cantons in Switzerland rely on the drought.chExternal linkplatform, which was set up in 2013. The tool, run by the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), provides information on a variety of hydrological indicators, from lake levels and river flows to the water equivalent of snow in the mountains.
With the new drought warning system, a national network of sensors will be created to measure soil moisture in real time. The system, which will cost CHF4.75 million ($5.2 million), will integrate hydrological data from the WSL platform and data from satellites that monitor weather conditions. It will provide information on all types of droughts.
The system will be gradually improved based on the experience of users, such as farmers. The goal is to predict the onset of drought several weeks in advance.
What are other countries doing?
Switzerland draws inspiration from the solutions of countries that have been most affected by droughts, says Christoph Spirig of MeteoSwiss. Among them is the United States, which introduced a drought monitoring systemExternal link in 1999. It consists of a map updated weekly showing the intensity of droughts.
Members of the European Union rely on the European Drought Observatory. This tool, introduced in 2007, is based on the analysis of rainfall, soil moisture, groundwater levels and vegetation water stress, among other indicators.
But one third of the world’s population is not covered by systems that warn of droughts or other extreme weather events. In 2022, the United Nations launched the Early Warnings for All initiative, involving multilateral agencies and development banks, humanitarian organisations and civil society. The initiative initially covers 30 countries most at risk. The goal is to protect all people on the planet from hazardous weather, water or climate events through early warning systems by 2027.