Droughts are increasing in Switzerland due to climate change. Droughts can be a challenge for agriculture, energy supply, ecosystems and other areas. This is where the project 'Development and expansion of an early detection and warning system for drought' comes in. Starting in 2025, the federal government will provide a new drought platform with information for early detection (monitoring and forecasting) and warnings for all of Switzerland.
- Why do we need information on drought?
- What is the aim of the drought project?
- Which (federal) offices and agencies work together on the drought project?
- What causes drought?
- Who is affected by drought?
- Where can I find the drought platform and what content does it include?
- What possibilities exist for dealing with future droughts?
Why do we need information on drought?
Extreme natural hazard events are increasing due to climate change. They can occur more frequently, with more severity and in places not previously affected. More frequent and longer droughts are one example of this increase in natural hazard events. The climate scenarios for Switzerland show that this trend will continue.
The federal government has therefore decided to include drought in its natural hazard warnings and to make measurement data, forecasts and related information available online on a drought platform starting in 2025.
With good information and timely warnings, the responsible cantonal and communal authorities, the economic sectors and the public can better prepare for periods of drought. This enables them to plan early and initiate suitable measures. Examples include:
- Communes: securing the drinking water supply and preparing information and recommendations for the public
- Agriculture: planning/optimising irrigation management
- Ship traffic/transport: planning alternatives to freight traffic on the Rhine
What is the aim of the drought project?
A national system for drought monitoring, forecasting and warning supplements the existing services of the federal government relating to natural hazards information and warning and implements the Federal Council decree of 18 May 2022. (Press release available in german, french and italian.)
A new drought platform will make information and data available online for this purpose starting in 2025. The drought data collected can be used not only for incident management, but also for science. The data helps to improve understanding of the direct and indirect effects of drought and to recognise important connections.
The drought warnings in particular make it possible to take precautions and react in a timely manner to prevent or minimise damage.
Which (federal) offices and agencies work together on the drought project?
Drought is a multifaceted phenomenon. Consequently, several federal offices work together on this project. These are: the Federal Office for the Environment (FOEN), the Federal Office of Meteorology and Climatology (MeteoSwiss) and the Federal Office of Topography (swisstopo). Each office is responsible for a different aspect in accordance with its area of expertise:
- The FOEN manages the project, coordinates the development of the information platform and the warning chain (in collaboration with the Steering Committee on Intervention in Natural Hazards LAINAT) and is responsible for monitoring and modelling hydro(geo)logical and forestry impacts. The FOEN publishes the warning in consultation with the other federal offices.
- MeteoSwiss is responsible for developing and operating the national soil moisture monitoring network. It also compiles and optimises drought indices (e.g. for the accumulated precipitation deficit) for monitoring as well as meteorological forecasts over extended periods (four weeks).
- swisstopo is Switzerland's geoinformation centre. It provides data from satellites for drought monitoring with a spatial resolution of up to 10 metres. Both current and historical data is provided. One example is the monitoring of vegetation stress (the extent to which plants suffer from drought) using satellites, which swisstopo performs together with MeteoSwiss.
What causes drought?
In contrast to other natural hazards, drought is a phenomenon that builds up slowly. When many people hear the word 'drought', they immediately think of summer and hot weather. But drought can also occur in winter. Drought depends in general on the following factors:
- Precipitation: This is the amount of rain or snow that falls in an area.
- Soil moisture: This is the amount of water in the soil.
- Discharge/water level: This is the amount of water stored in bodies of water or as groundwater.
A drought is therefore always a water shortage, regardless of the time of year.
What types of drought are there?
The World Meteorological Organization (WMO) distinguishes between four types of drought, which differ in their origin and effects:
Meteorological drought (precipitation deficit)
Agricultural drought (soil moisture deficit)
Hydrological drought (discharge deficit)
Socio-economic drought (supply deficit)
Meteorological droughts are characterised by below-average precipitation (precipitation deficits) over several weeks to months. This is due to persistent areas of high pressure that keep out moist air masses.
If there is no precipitation for an extended period of time, the soil moisture also decreases. This means that less water is available for plants. In the summer half-year, the reduced soil moisture is often a result of a combination of low rainfall and high evaporation due to high temperatures. This is the case, for example, when a dry winter is followed by a spring with little precipitation and then periods of heat in the summer months.
When the water level in rivers, lakes and groundwater falls far below the long-term average, this is referred to as hydrological drought. This situation is exacerbated by increased water abstraction, e.g. for irrigation.
If the water demand of the population and the economy is higher than the available supply, this is referred to as socio-economic drought.
What all these types of drought have in common is that there is not enough water available in an area over an extended period of time to meet the current water demand. However, exactly how much is 'enough' varies depending on the sector and population concerned. In a given region, the soil may already be very dry, affecting agricultural production. However, there may still be enough water left in the bodies of water of the same region so that fishing and water ecology are not (yet) affected.
Soil: water storage and evaporation
The increasing drought has a strong impact on soil moisture. In combination with above-average temperatures and sunshine hours, this leads to the soil drying out considerably. The type of soil also plays a crucial role. While sandy soil, for example, cannot retain water well, clayey or organic soil can store water over a longer period of time.
The less water there is in the soil, the less water can evaporate from the soil surface, which leads to further warming and drying of the atmosphere. At the same time, fewer clouds form and it rains less. This dries out the soil even more.
In this case, does a heavy downpour help to resupply dry soil with sufficient water? Not necessarily. Very dry soil may not be able to allow rainwater to seep away quickly enough. The water simply runs off the rock-hard, crusted surface. This can lead to flooding and flash floods. This is also called 'surface runoff'.
Who is affected by drought?
The following areas can be negatively affected by drought:
Drinking water supply
Energy supply/electricity sector
Agriculture
Forestry
Ship traffic/transport
Nature/ecosystems/biodiversity
Population
Some sources of drinking water may dry up. Moreover, supply bottlenecks may occur and thus conflicts of use between the drinking water supply and other uses (e.g. irrigation in agriculture). The supply of extinguishing water may also be affected. This is especially important because the risk of forest fires increases in dry weather.
When rivers carry less water due to drought, run-of-river hydro power plants are not able to produce as much electricity. Storage power plants also produce less electricity due to the low reservoir levels.
When water levels are low, bodies of water warm up more quickly. Cooling water for nuclear power plants, which is normally taken from rivers, is then too warm. Moreover, river water heats up further due to the operation of the nuclear power plants.
Heat and drought lead to a rapid decrease in soil moisture. This damages plants and leads to crop losses or even crop failures (due to drying out, emergency harvests from insufficiently developed seeds, plant diseases, etc.). If there is no rainfall, dry soils can be irrigated. This causes the (ground) water level to drop, however. This is not always sustainable and can lead to further problems, especially if the water level is already very low due to drought.
In the worst-case scenario, farms are forced to slaughter livestock because the livestock can no longer be supplied with sufficient feed without additional feed purchases or because there is no longer enough drinking water available. This affects alpine farms in particular.
Crop and livestock losses not only have an impact on producers, but also on consumers: If the food supply becomes scarcer, prices rise.
Trees react stressed to a lack of water and are weakened as a result. They grow more slowly and produce less fruit or none at all. Prolonged drought can cause leaves to change colour or can cause trees to shed leaves or needles prematurely. Weakened trees are also more susceptible to insect infestation, e.g. bark beetles. Drought can lead to the death of treetops or entire trees. Falling branches or falling trees can then be dangerous for visitors to the forest. Trees then also no longer offer protection against natural hazards (protection forest). Drought also increases the risk of forest fires, given that more combustible material (fuel) is available.
Passenger and freight shipping is negatively affected by low water levels. This also applies to leisure traffic on the waterway network, which can no longer take place regularly. Transport shipping on the Rhine, which is important for the import and export of goods to and from Switzerland, can be severely impaired by low water levels (reduced speed and/or loading capacity) and, in the worst case, must be suspended. This has an impact on commerce and can affect the national economic supply (e.g. shortages of animal feed, edible oils/fats, fuels).
Various ecosystems are affected by drought, sometimes severely. For some species, the situation is even life-threatening. Water-dependent ecosystems and forests suffer especially severely from long periods of drought. Drought causes water levels to fall and water temperatures to rise, which reduces the oxygen content in the water and concentrates any pollutants the water may contain. These factors put fish under stress and can cause fish to die off.
Tree mortality increases. This not only threatens biodiversity, but also human beings and their basic resources/material assets, e.g. through forest fires or weakened protection forests.
Nitrate/pesticide inputs into the groundwater – especially from agriculture – are diluted less during droughts. Similarly, discharged waste water is also diluted less.
In general, droughts lead to a decline in water reserves (low water in lakes, rivers and groundwater reservoirs). In some cases, this can lead to water shortages in households. Where shortages are severe, communes may call for restrictions on water use (e.g. no watering of gardens and lawns, no washing of cars). In the event of water shortages, conflicts can arise between different users and interest groups with regard to who is allowed to consume how much water.
Dry vegetation increases the risk of forest, field and bush fires. In populated areas, this creates a risk of injury to persons and damage to property. If many fires occur at the same time, there may be a shortage of available resources (fire engines, helicopters, firefighters).
If there is heavy rainfall after a drought, local flooding may occur. The dried-out soil cannot absorb the water quickly enough, and large surface runoffs occur (see info box 'Soil: Water storage and evaporation').
© KEYSTONE/Cyril Zingaro
Where can I find the drought platform and what content does it include?
The federal government's new drought platform goes online in spring 2025. A wide range of information on the current situation and forecasts for the coming four weeks will be made available at www.drought.admin.ch, along with historical data (e.g. precipitation, discharge, soil moisture, groundwater, vegetation stress). If extended droughts occur, warnings are also published on the platform.
Starting in 2025, the drought platform will be further developed and expanded on an ongoing basis.
The drought platform is based on the existing platform drought.ch of the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL). The website drought.ch will continue to operate as an experimental research platform once the new drought platform goes live.
What possibilities exist for dealing with future droughts?
The local effects of droughts can differ significantly. It is therefore important to obtain timely information and to follow the instructions of the local authorities if a drought occurs. More information on how to act during a drought will also be available starting in spring 2025 on the federal Natural Hazards Portal.
In the longer term, forward-looking adaptation strategies are needed to deal with increasing periods of drought. A few examples:
- In agriculture, crops that require less water can be used. Irrigation methods can also be optimised. Smart soil moisture sensors can report when and how much water is needed. This ensures that irrigation is selective and performed only when it is really necessary. This saves water.
- Water suppliers can increase their resilience to drought primarily through better networks. This includes the development and coordination of joint emergency plans between the various suppliers. These plans can define joint strategies in the event of extreme drought, such as the temporary redistribution of water resources. However, this requires investment in infrastructure, e.g. the construction of supra-regional pipeline networks. Networks create flexibility and ensure that bottlenecks can be compensated for locally so that the drinking water supply remains reliable even under difficult conditions.
- Forestry aims to make forests more resilient so that they remain healthy in the long term and can continue to fulfil their functions (as a source of wood, protection against natural hazards, habitat, etc.). For example, more tree species can be planted that cope better with drought.
But as is so often the case, the following principle applies here as well: Prevention is better than cure. Instead of adapting to increasingly long and more frequent droughts, active climate protection (e.g. through the reduction of climate-damaging emissions) can significantly mitigate the increase in droughts, heat, heavy precipitation and lack of snow.
Further information
Last modification 19.08.2024
