Rishma Banerjee

Droughts followed the prolonged heatwaves in Europe, drying up the water level of rivers, streams and underground

Since May 2022, Europe has been facing several climatic extremes, with heatwaves, wildfires, drought conditions, and flash floods reported across the continent. Drought conditions have affected the continent since the beginning of 2022, but it is now expanding. According to the researchers at the European Drought Observatory, the combined drought indicator (CDI) shows that 47 per cent of Europe is under "warning conditions" and 17 per cent is under "alert conditions". The European Commission Joint Research Centre (EC-JRC) has warned that the current drought could be the worst in 500 years.

Mapping
Drought hazards have been increasing in Central and Southern Italy, Southern Greece, Spain, Portugal, France, Western Germany, the Netherlands, Belgium, Luxembourg, Romania, Hungary, northern Serbia, Ukraine, Moldova, Ireland, and central and southern UK.

The Po River is under the highest drought severity in Italy, where water levels are seven feet lower than usual. Italy's Prime Minister Mario Draghi described the situation as the "most serious water crisis in 70 years". To compensate, more water from Lake Granda was allowed to flow out to local rivers but even that had to be stopped when the lake's water level reached just 32cm above the water table. Drought emergencies have been declared in five Italian regions along the Po basin, home to nearly 30 per cent of Italy's population.

The Iberian Peninsula comprising Spain and Portugal has been severely affected too. In Spain, reservoirs were at 40 per cent capacity by the end of July. The volume of water stored in reservoirs is currently 31 per cent lower than the 10-year average. Such is the drought in the country that a pre- historic stone circle called the Spanish Stonehenge has emerged on the Valdecanas reservoir. In Portugal, the water reservoirs that store hydroelectric energy are at less than half the average of the last five years. Water for irrigation has also been affected.

In France, around two-thirds of the country is under a crisis alert. French Prime Minister Elisabeth Borne reported that July 2022 was France's driest month in 60 years. 100 villages have run out of water and depend on water supply trucks. On 05 August, an inter- ministerial crisis unit was set up to mitigate the potential crisis. The agricultural ministry said that the corn harvest has been affected due to water scarcity and is expected to be 18.5 per cent lower than in 2021. Even though Europe is anticipating an energy crisis, nuclear power stations are reducing their outputs. High water temperatures and low flows have affected their ability to use river water to cool the plants.

In Germany and Netherlands, the Rhine River has reported such a low water level that freight is being loaded to only 30-40 per cent of the capacity to avoid running aground. The Rhine is the main artery for shipping in the two countries, and thus, low flows severely impact commercial navigation and the logistics sector. In the Netherlands, dike stability and water distribution have also been affected.

In the UK, July was the driest month since 1935, with only 35 per cent of the average monthly rainfall. The reservoirs are at a 25- year low; on 12 August, a drought was declared in 8 of the UK's 14 environment agencies.

Recent occurrences
Studies show a robust greenhouse-gas- forced temperature change in temperatures in the first half of the 20th century (1900- 1949). Observational datasets confirm that human activities affected the tendencies of droughts across Europe during this time.

The major drought in this time frame occurred in 1921 and 1947. In 1921, the drought was driven primarily by a significant rainfall deficit. The worst hit area was the triangle between Brussels, Paris, and Lyon, and a vast stretch of the continent, from Ireland to Ukraine was also affected. It impacted water supply, agriculture and livestock farming. The drought of 1947 was of exceptional severity and spread across Central Europe. It originated due to an anticyclone over Central Europe and the ridges of high pressure extending over the region. It led to a terrible harvest of cereals and other crops.

However, in the mid-20th century (1950- 1980), a decrease in drought tendency is revealed, and greenhouse gases are seen to have a lesser impact on sporadic dry spells across Europe. Increased aerosol pollution and frequent volcanic eruptions also blocked sunlight and induced more rainfall than the average. The major drought that affected Europe during this time was 1975-76. This was brought about by a relatively dry, mild winter with below-average precipitation. The precipitation deficit developed during spring and summer over Western Europe, centring in northwest France and southeast England. While the drought in 1975-76 was not the only one in this time frame, the remaining recorded ones were lesser in intensity and extent and had faster turn- around timelines.

In the later part of the century (1980-2000), an increased compound influence of greenhouse gas on droughts is noted again. The major drought incidents in this time frame started in the winter of 1989 and 1991. The drought conditions that affected the Iberian Peninsula in 1989-90 were less severe in intensity, but they heralded dry conditions that prevailed over Europe throughout much of the early 1990s. This event had two peaks, one in the spring of 1989 and the next during the summer of 1990. While the former was mainly restricted to Spain and Portugal, the latter expanded north and westward to affect southern France. From 1996-1997, the drought began with meteorological shortages in Great Britain and expanded over south Scandinavia, Denmark and northern Germany. It started with a dry winter and reduced available water for Europe in the early spring.

In the 21st century, droughts have been a common occurrence across Europe. These droughts have been regarded as exceptionally severe and linked primarily to increased temperature, heat waves, and a lack of precipitation in the summer months. 2003, 2015, and 2018-2019 saw the most intense drought events in this time frame, other than the ones currently affecting Europe.

In 2003, the drought resulted from increased evapotranspiration due to significant precipitation deficits with heat extremes. Due to the drought, crop yield suffered significantly, and low discharge levels of rivers were reported across Europe. In this case, the drought conditions expanded rapidly because of the persistent blocking of the high-pressure pattern that lingered over Western Europe. From 2004-2007 several parts of Europe underwent drought conditions. While the intensity was considerably lower in Western Europe, like France and the UK, this episode is considered one of the worst drought events for Spain and Portugal. It affected hydropower and crop production severely. Such was the disaster in Portugal that the country declared a "calamity status", a temporary "Drought Commission" had to be established.

In 2015, over 50 per cent of Europe was affected by severe drought. It developed rapidly over the Iberian Peninsula, France, southern Benelux, and central Germany in May. It reached peak intensity and spatial extent by August, affecting especially the eastern part of Europe. Over the summer period, four heat wave episodes were associated with persistent blocking events.

The 2018-2019 drought was due to extremely high temperatures and increased evapotranspiration rates. Record-breaking high temperatures reached the otherwise cool and humid northern regions, and the compound hot-dry event led to major impacts in north-central and north-eastern Europe, particularly affecting agriculture, livestock farming and forestry as reported for Sweden, Finland, Estonia, Lithuania, Latvia, Denmark, the Netherlands, Belgium, Germany, the United Kingdom, and eastern France. The propagation of the meteorological drought resulted in low reservoir levels and river discharge, which period, four heat wave episodes were associated with persistent blocking events.

The 2018-2019 drought was due to extremely high temperatures and increased evapotranspiration rates. Record-breaking high temperatures reached the otherwise cool and humid northern regions, and the compound hot-dry event led to major impacts in north-central and north-eastern Europe, particularly affecting agriculture, livestock farming and forestry as reported for Sweden, Finland, Estonia, Lithuania, Latvia, Denmark, the Netherlands, Belgium, Germany, the United Kingdom, and eastern France. The propagation of the meteorological drought resulted in low reservoir levels and river discharge, which impaired public water supply, leading to partial shutdowns of nuclear power plants and triggering massive fish deaths. In contrast to central and northern Europe, the western Mediterranean countries experienced above‐average wet conditions in 2018. Opposite to 2018, the 2019 drought was centred on eastern Germany, the Czech Republic, and Poland before spreading westward

It can thus be noted that regional droughts are a regular occurrence, especially in Southern Europe. However, the extent of the dry spell in 2022 is showing signs of being exceptional.

Tracing the causes
First, Europe's current weather and wind patterns. The jet stream current usually brings the wet Atlantic winds to Europe. However, the lessening of temperature differences between regions has weakened the intensity of the stream. Thus, instead of bringing in moisture-laden winds, a weak or unstable jet stream is bringing hot air from North Africa into Europe, leading to more intense heat and drought. Moreover, most of the continent has noticed high mid- tropospheric pressure anomalies, which are associated with heatwaves and droughts. These steer away continental weather systems that bring moist and cool air.

Second, prolonged high temperatures and wildfires. The droughts are both a cause and an effect of the sweltering summer in Europe. Hot weather dries up the landscape, which dries up the atmosphere and makes the air easier to heat up. As evapotranspiration increases, high-pressure 'heat domes' are created that deflect precipitation, thus enhancing the severity of droughts.

Third, climate change, global warming and anthropogenic causes. Climate change has increased Europe's average temperature by 1.9 degrees Celsius compared to pre- industrial levels, which is faster than the world average. As a result, rainfall patterns are shifting, whereby they occur in shorter and more intense bursts, often not in unity with the monsoon season. Thus, non- perennial rivers do not replenish their water levels, and water retention in the soil also becomes difficult. Absorption of this water to fill the underground water table also becomes difficult, thus exacerbating agricultural drought. The rise in temperature evaporates more water, therefore drying up land further. This climate change has also been caused by human behavior in the form of industrialization, fossil fuel use, and increased water demand for civilizational use has also exacerbated the anomalous weather patterns. Though human activity has not been an immediate trigger for the 2022 drought, the effects accumulate and compound over the years to have an adverse impact on the environment.

While droughts have been a regular occurrence in the history of Europe, the current one persisting over an extensive part of the continent is showing signs of being intense and long-lasting. The 2022 drought is exacerbated by the climate anomalies like heatwaves and wildfires that Europe is experiencing. This has increased the demand for water, which the continent is not equipped to provide. This drought, especially amidst an impending energy crisis, will be brutal for Europe to mitigate.

About the author
Rishma Banerjee is a Research Assistants at the School of Conflict and Security Studies, NIAS.

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