Drought is an extreme, prolonged condition in which less water or rainfall is available than necessary. Drought is not only a physical phenomenon, but also an interplay between the availability and the water demand of organisms .
Drought often occurs in areas with a continental climate .
Typology of drought events
In general, three types of conditions are referred to as drought:
- Meteorological drought or climatological drought occurs when precipitation falls below average over a longer period of time.
- Hydrological drought occurs when the water levels in the water body fall below a normal value ( low water ) and the water reserves in the lakes , water reservoirs or water storage facilities fall below the statistical average. The shape is the longer-term consequence of the meteorological drought
- Soil dryness and, as a result, agricultural drought occurs when there is a lack of water in the root layer of the soil profile and there is too little water for an average agricultural production of crops . This can be due to long-term insufficient precipitation, but also have other reasons for a falling groundwater level (such as excessive abstraction , shifting of groundwater flows ), but also be a fundamental soil or area characteristic of soil or land (see also turgescence , turgor ; wilt ).
Drought periods can occur regularly, depending on the climate profile ( dry summer climate , winter drought , etc., compare singularity ), or an exceptional event that can last for weeks or years ( extreme weather ) , or a largely permanent climatological or regional condition (see, for example, desert climate , desertification , Karst , Inner Alpine Basin ), which changes on a geological scale. A hybrid form is the periodic but irregular El Niño phenomenon, which can trigger floods in South America and droughts in Africa .
There are various systems for quantifying drought, such as the Palmer Drought Index .
See also : Drought Index
A mega-drought is a drought that lasts for at least a decade or, more generally, particularly intense or long-lasting drought.
Possible consequences of droughts
- Bottlenecks in the water supply
- lower harvests , high prices for the harvested goods
- less cattle feed, high prices for animal products
- Obstruction of shipping due to the low water level.
- Bottlenecks in the power supply :
- Hydropower plants can produce less electricity
- The delivery of hard coal-fired power plants by ship becomes more complex at low water levels (the cargo ships cannot be fully loaded)
- Thermal power plants have to throttle their output, especially in summer (on the one hand they have too little cooling water in terms of quantity; on the other hand, the cooling water may only have a certain maximum temperature when it flows back into the river. The warmer the water is before it is withdrawn, the less the cooling capacity can be deliver it).
- Forest fire - and hallway fire risk (potentially: wildfire )
- Soil erosion
- Sand and dust storms
Drought risk analysis
As part of the risk analyzes in civil protection carried out by the German Federal Office for Civil Protection and Disaster Aid (BBK), the drought risk analysis was published in 2018 .
The drought scenario analyzed extends over six years and is derived from the extreme drought in Germany from 1971 to 1976. A return probability of around 450 years was estimated for this event. An increased mortality was determined due to the heat wave and cold spell. The examined effects of the drought scenario on critical infrastructures in Germany produced a large number of indications of identified deficits and suggestions for improvement.
List of historical disasters
|22nd century BC Chr.||Catastrophic drought in eastern North Africa and parts of the Middle East.||Fall of the Old Kingdom in Egypt and the Akkadian Empire in Mesopotamia .|
|Late 8th century BC Chr.||Drought in Greece.||Possibly trigger of the Lelantic War between Chalkis and Eretria|
|9th and 10th centuries||Three severe drought periods of several years 50 years apart (around 810, around 860, around 910).||The classical Maya civilization collapsed.|
|1069||England||Drought: almost 50,000 people starved to death. Many had to sell themselves into serfdom to survive.|
|1199 and 1202||Egypt||There was no annual flood of the Nile . 100,000 people starved to death.|
|1669-1670||India||Famine in Bengal in 1770 - an estimated 10 million deaths.|
|1876-1877||India||Three million people died of malnutrition and three million of cholera. A total of 36 million people were affected by the disaster.|
|1930-1938||Three years of drought (1930, 1935, 1937) within a decade in North America , known as the " Dust Bowl ".||Harvest failures, depopulation of some areas in the Midwest.|
Hot or drought years in Germany
The drought of 1540 is described by some authors as "the worst drought of the millennium in Germany", but this thesis is doubted by others. An investigation showed that during this time there was hardly any rain for 11 months, an event that cannot be simulated by today's climate models. The temperatures are said to have been five to seven degrees above the mean of the 20th century.
In 1857 a drought in the Emsland had a significant impact.
2003 was a so-called summer of the century . From around August 1st to 15th, 2003, there was a heat wave in large parts of Europe.
The first half of 2011 was extremely dry in Germany. The weather in the months of March, April and May ("spring") 2011 summarized the German Weather Service u. a. so together:
- "At 10.1 degrees Celsius, the second warmest spring since 1881" ("2.4 degrees higher than the climate value of 7.7 ° C")
- "The sunniest spring since the sunshine measurements began in 1951." (699 hours - a good 50 percent above the long-term average of 459 hours) * "Extreme drought, especially in central Germany"
- “With an average of 88 liters per square meter (l / m²) - the average is 186 l / m² - Germany experienced the second driest spring since measurements began 130 years ago. Most of the rain still received the areas on the immediate edge of the Alps. ... It was the driest in southern Rhineland-Palatinate, northern Baden-Württemberg, Hesse, Lower Franconia and southern Thuringia. ... Agriculture in particular suffered from the great drought. The meadows were ready to be cut early, but the yields of hay and grass silage were low. The grain remained in growth and showed clear signs of emergency ripeness at the end of May . In May, the levels of most of the German rivers were lower than they had been for about 100 years at this time of year. "
Another drought occurred in autumn 2011. September and October brought below-average rainfall; November was in some areas the driest November since weather records began.
Spring and summer 2018 were marked by an unusual drought in Germany and other European countries. There were crop failures, low water levels and numerous forest fires. A similar picture emerged in 2019.
Bavaria has been operating a low water information service (NID) since 2008 . It provides information online about precipitation, groundwater levels, water temperatures and water levels in rivers and lakes. In this way, water suppliers, agriculture, business or tourism receive prepared information and can take preventive measures. Municipalities can, for example, restrict lawn sprinkling, farmers can adjust their irrigation and water-intensive industrial companies convert their production.
The 2020 drought period primarily affects “Saxony, parts of the Danube catchment area in Bavaria and regions on the Middle Rhine in North Rhine-Westphalia”, although drought has been a problem for Germany for two years. Therefore, there are considerations that the state should set a priority list of who is allowed to use water in which order.
The Mediterranean countries in Europe are particularly affected by long dry seasons that exceed the average .
In 2007, months of droughts and numerous forest fires occurred in Greece , Spain and Portugal . In places, almost the entire forest fell victim to the flames, which is partly due to arson caused by soil speculation . New laws for a long-term construction ban are intended to prevent this.
In large parts of Spain , extreme drought prevailed from spring 2007 to 2010 - in some provinces it did not rain for 18 months. The distribution of precipitation in 2007/08 was very different from region to region: while the 1½-year drought prevailed on the Mediterranean Sea, in April 2008 there were floods in Andalusia and the northern Spanish provinces.
The regional authorities fought the shortage of drinking water on the coast with desalination plants , which was not enough to irrigate the crops. The use of tankers was therefore planned from the beginning of 2008 and an appeal was made to EU solidarity. The northern provinces, which are richer in water, rejected water transport to the south.
- Robert K. Booth et al. a .: A severe centennial-scale drought in midcontinental North America 4200 years ago and apparent global linkages. In: The Holocene . Volume 15, 2005, pp. 321-328 ( doi: 10.1191 / 0959683605hl825ft ).
- Gerald Haug et al. a .: Climate and the Collapse of Maya Civilization. In: Science . Volume 299, 2003, pp. 1731-1735. ( doi: 10.1126 / science.1080444 ).
- John McK. Camp II: A Drought in the Late Eighth Century BC In: Hesperia . Volume 48, 1979, pp. 397-411 ( doi: 10.2307 / 147843 ).
- Benjamin I. Cook: Drought - An Interdisciplinary Perspective. Columbia University Press, New York 2019, ISBN 9780231176897 .
- Armin Opherden: The low water of the Rhine in November 2011 compared to the record measured in September 2003. Private homepage, December 2011, accessed on November 17, 2013 .
- Claudia Krampe: International drought disasters. In: Naturgewalt.de. Archived from the original on April 21, 2012 ; Retrieved November 17, 2013 (probably 2004).
- EDO - European Drought Observatory (with data from the Copernicus Earth observation program )
- ↑ For a clear, well-illustrated explanation of the distinction between climatic dryness, dry ground and hydrographic dryness (low water) see, for example, Sucho ( memento from October 16, 2015 in the Internet Archive ) , Czech Hydrometeorological Institute (chmi.cz, in Czech).
- ↑ NZZ.ch April 25, 2016: Water crisis in Ethiopia - The government is ashamed of the drought
- ↑ John A. Matthews: megadrought . In: Encyclopedia of Environmental Change . tape 3 , 2014, p. 684 , doi : 10.4135 / 9781446247501.n2421 ( online ).
- ↑ spiegel.de May 29, 2011: Drought threatens power supply in Germany
- ↑ The heat wave throttled electricity production of conventional power plants - Solarenergie-Förderverein Deutschland eV
- ↑ Report on the risk analysis in civil protection 2018 , in: 19th German Bundestag , printed matter 19/9521, April 12, 2019 - Risk analysis drought.
- ↑ a b c d e Karsten Schwanke , Nadja Podbregar, Dieter Lohmann, Harald Frater: Natural catastrophes. Hurricanes, earthquakes, volcanic eruptions - Unleashed violence and their consequences , Springer-Verlag Berlin and Heidelberg 2009, ISBN 978-3-540-88684-6 , p. 193 (listing "historically significant droughts" without detailed information and without references)
- ↑ Oliver Wetter u. a .: The year-long unprecedented European heat and drought of 1540 - a worst case . In: Climatic Change , June 2014, doi: 10.1007 / s10584-014-1184-2
- ↑ Axel Bojanowski : Heat and Drought 1540: Weather data reveal Europe's largest natural disaster . Article from July 6, 2014 in the portal spiegel.de , accessed on July 6, 2014
- ↑ a b Jan Grossarth: Millennium Drought 1540: The worst summer of all time. Frankfurter Allgemeine Zeitung , August 3, 2018, accessed on August 4, 2018 (newspaper article behind Paywall or in the print edition of August 3, 2018, page 16).
- ↑ Amartya Sen (1981): Poverty and Famines: An Essay on Entitlement and Deprivation , p. 39 ( online )
- ↑ Büngten et al., (2015): Commentary to Wetter et al. (2014): Limited tree-ring evidence for a 1540 European 'Megadrought'; Climatic Change, July 2015, Volume 131, Issue 2, pp 183–190, doi : 10.1007 / s10584-015-1423-1 .
- ↑ Oliver Wetter, Christian Pfister, Johannes P. Werner et al .: The year-long unprecedented European heat and drought of 1540 - a worst case . In: Climatic Change . tape 125 , no. 3-4 , August 2014, pp. 349-363 ( springer.com ).
- ↑ Andreas Frey: Eleven months without rain: The fear of the mega-drought of 1540 is about. Neue Zürcher Zeitung , August 4, 2018, accessed on August 6, 2018 .
- ^ Great drought in Emsland - Agricultural situation report from 1857 - Arenbergische Korrespondenz Rentmeister Schürmann. www.porto-club.de, 2011, archived from the original on January 8, 2018 ; accessed on August 4, 2018 .
- ^ Rommerskirchen: Great drought and hail projectiles. NGZ online ( Neuss-Grevenbroicher Zeitung ), August 29, 2006, accessed on August 4, 2018 .
- ↑ German Weather Service: May April 2011 March 2011 February 2011 January 2011
- ↑ Press release from May 30th, 2011: Sunniest spring since measurements began. German Weather Service , May 30, 2011, archived from the original on September 23, 2015 ; accessed on August 4, 2018 .
- ↑ Bavaria Low Water Information Service
- ↑ Heike Holdinghausen: hydrologist on the 2020 drought period: “We are running out of water”. In: The daily newspaper . July 6, 2020 .
- ^ Daniel Lingenhöhl: Thirsty city. Die Zeit , June 22, 2009, accessed on August 4, 2018 .