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Drought in the Swiss water tower

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In the long run, it will not only be hotter in Switzerland, but also drier. Droughts have serious consequences for agriculture, water supply, energy production or natural ecosystems. We are creating the data basis to recognize critical droughts at an early stage and to assess and mitigate their consequences for nature and society.


From an economic and social perspective, as well as for risk management, early detection of critical drought conditions is essential. On our platform, a wide range of hydrological indicators are combined in a nationwide early drought detection system. The platform serves as the basis for a national federal early warning system for drought in Switzerland. In addition, we develop models and study large-scale weather situations in order to be able to predict water deficits several weeks in advance.

Heat waves and the associated extreme droughts are on the rise as global warming progresses. In the Alpine region in particular, they have the potential to trigger social and economic crises, for example if natural hazards become more frequent or cause worse damage than before. The CERC research center contributes to a better understanding of these extremes and their risks, and to finding solutions to mitigate or manage them for the benefit of society.

Today's lack of snow is potentially next summer's drought. The SLF has compiled questions and answers on the winter of 2022/23 with little snow.




Alpine Drought Obvservatory

According to the Alpine Convention, water scarcity and related conflicts are becoming a worrying topic in many Alpine regions, depending on water from snowmelt and glaciers.

EMERGE - Extreme droughts in mountain regions

EMERGE will investigate the impacts of historic megadroughts on water fluxes and ecosystems in mountain regions, and use this knowledge to develop stress-test scenarios for a possible future megadrought in the Swiss Alps.


This research aims to explore the predictability of drought at a monthly time horizon in the form of low flow in Switzerland and the European Alps by using machine learning techniques and linking large scale weather patterns with local hydrological events.

Floods and droughts under global change

This project aims to enhance our understanding and modeling capability of regional hydrologic extremes in the Alps in a global change context.

Drought and flood statistics in regulated catchments

This project aims to enhance our understanding of the statistical behavior of multivariate hydrologic extremes in the Alps in a global change context where streamflow is increasingly regulated through reservoir operation or water abstraction.


Drought has been one of the main focus topics of WSL forest research for years. In Valais, we oversee various research platforms and conduct irrigation experiments in the Pfynwald. Building on this experience, we are extending our research to other, hitherto less arid forests in Switzerland. Indeed, the increasingly frequent dry and hot years are also leaving their mark on the Central Plateau, the Pre-Alps and the Jura.

On numerous observation plots, we have been doing intensive surveys on forest health for many years and also measure the effect of drought on forest condition. These are the plots of the Long-term Forest Ecosystem Research (LWF) and the Sanasilva inventories. In addition, we also conduct annual forest health surveys on the 6000 sample plots in the National Forest Inventory (LFI) network.

The real-time network TreeNet calculates daily so-called forest condition nowcasts, which provide information about the current tree growth and tree water deficit (a measure for drought stress of trees) of about 400 forest trees all over Switzerland. The indicators are displayed daily on These data are also integrated in the federal NCCS site on forest functions and climate change, where further data on current forest condition can be compared in an interactive internet tool (Forte app).

In the 2018 summer season, Switzerland (and especially Central and Northern Europe) experienced one of the most extreme droughts in recent decades. In the same year, WSL launched the WSL Drought Initiative 2018 with the aim of deriving new insights for dealing with similar situations in the future.

For more information, see our Forest and drought page.




VPDrought: A novel approach to disentangle atmospheric and soil drought

By deciphering the single vs. combined VPD and soil moisture effects, we will be able to improve global predictions. We aim to apply a scale spanning approach to disentangle the processes affected by atmospheric (i.e., VPD) and soil droughts from the tissue to the tree and the ecosystem level.

SwissSPOT- Swiss forest Soil water POTential network

SwissSPOT is a network to monitor soil water down to 2m soil depth at Swiss Long-term Forest Ecosystem Research (LWF) sites.

HEAT - Keeping it cool in a Hotter world: brEAking new ground into the drivers and consequences of forest Temperature regulation

We will use a hierarchical cross-scale approach that spans plant physiology, remote sensing, and community ecology to assess the physiological and ecological processes that underpin forest temperature regulation during hotter droughts. The work will take place at the Model Ecosystem Facility (MODOEK) and in Saillon (Valais).

Detecting temperature thresholds for photosynthesis and understanding how they are controlled by long-term acclimation to soil drought

We evaluate the potential of thermal imaging with unmanned aerial vehicles (UAV) to detect drought stress in Pinus sylvestris in a long-term irrigation experiment in the Pfyn forest in Valais (southern Switzerland).


Species-specific reactions of temperate European forest trees to a changing environment. A project related to the Swiss Canopy Crane II (SCC II) site near Basel and the network TreeNet.

Drivers and consequences of drought-induced hydraulic dysfunctions and mortality under global warming

This project explores the specific impact of VPD and temperature increase on tree water use and mortality. It also investigates the potential damages of using X-ray MicroCT to track embolism in living trees.

Partitioning of resources between beech trees during drought

We will examine whether recent drought events shifted the partitioning of growth among tree size classes of beech trees and use this information to develop thinning strategies for mitigating drought impacts in lowland and montane Swiss beech forests

N-DEPEND - Is there a "Nitrogen Deposition Penalty" for Forests under Drought?

This project intends to test the "N-penalty" hypothesis for the Swiss forests. By statistical modeling and quasi-experimental analyses based on N deposition estimates, drought indices and NFI data, we assess interacting effects of N deposition and drought on forest health and productivity.

UAV-based monitoring of physiological tree responses

In this project, we investigate the potential of spectral proxies, obtained from unmanned aerial vehicles (UAV) high-resolution multispectral and thermal imaging, to detect trees pre-visual drought stress responses.

Acclimation and environmental memory

Which are the main mechanisms conveying adaptation on the organ and whole tree level, how fast does acclimation occur and how long is an acclimation potential sustained?

Oriental beech (Fagus orientalis) for assisted migration?

We assess the drought response of European and oriental across different life stages by taking advantage of existing Oriental beech plantations in France, Germany and Switzerland.

Soil organic matter dynamics under drought

DRYSOM assesses soil organic matter (SOM) to drought in a long-term irrigation experiment (Pfynwald). Responses range from a suppressed processing through microbial and faunal communities, decreases in carbon inputs from trees into soils, to shifts in soil carbon storage.


We want to explore a stable isotope tree-ring approach for analyzing physiological drought responses of trees. The results are expected to provide a novel diagnostic tool for understanding causes of tree decline.

Drought duration effects

The present study will analyze the within-tree distribution of C, N, and P reserves in trees treated with different drought duration and frequency, to investigate the C, N and P reserves in relation to recovery ability and mortality following repeated drought events with various drought duration.

Understanding how species interactions modulate long-term heat and drought impacts

The project aims to assess the physiological processes by which trees adapt and interact with each other under a changing climate, determine how these processes affect tree physiological responses to climatic stresses, and better understand long-term shifts in tree internal carbon and water cycles.

Forests under stress

In this project we will assess the physiological processes by which trees adjust and interact among each other under a changing climate, determine the consequences of these processes on forest responses to climatic stresses and improve our understanding of these effects on forests functioning at a large comprehensive scale.

Drought & beech: Effects of the 2018 summer drought on beech on the northern side of the Alps

In this project, we investigate causes for the impacts of the extreme summer drought 2018 on the vitality of beech trees in different regions of the Swiss Plateau and Jura.




How do beech trees in Switzerland react to extreme drought?

The WSL project "Drought and Beech" investigates possible causes of premature leaf discoloration and discoloration in the extreme summer of 2018 in the Swiss Plateau and Jura.



Capturing a forest's invisible stress

Researchers at WSL show how the stress of trees can be detected at an early stage. To do this, they use spectral data from drone photos.


Drought, heat and forests

Vapor pressure deficit (VPD) - the difference between the amount of moisture in the air and the amount of moisture the air can hold when saturated - determines how much moisture plants release. Its increase as a result of climate change is a concern for forests.



Surviving drought

At WSL, Leonie Schönbeck studies how trees absorb and store energy, and how they use their energy reserves to recover after drought.



Prolonged dry periods, which increase the risk of forest fires, have become more frequent in the last thirty years. We systematically collect data from forest fires and develop methods and concepts to assess forest fire risk.

Further information on the topic of forest fire on our topic page Forest fire.




Forest fire extremes in mountain regions

FoFiX tackles questions on the emerging fire hazard in regions not yet affected by forest fires, e. g. mountain regions of Central Europe.

Remote sensing data for fire danger rating

Provide a simplified Swiss-wide forest fire-related characterization of forest fuel types and calculate and analyse drought and fire-related remote sensing indices derived from multispectral Landsat and Sentinel-2 data.

Nearest neighbor fire rating

Development of a data-driven nearest neighbour model for the daily forest fire danger rating which may be used by the operators as second opinion provider.

Drought influence on lightning-induced fires

In a changing climate, lightning-caused wildfires might increase in Switzerland over the next decades. Our studies aim at understanding patters and conditions under which these fires develop.




Fire ecology of beech forests

In the context of climate change, forest fires in beech forests are becoming more frequent and severe. Against this background, the idea has arisen to initiate a specific study on the fire ecology of beech.