Difference between revisions of "Drought" - New World Encyclopedia
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[[Image:Fields outside benambra.jpg|thumb|300px|Fields outside [[Benambra, Victoria]], [[Australia]] suffering from drought conditions.]] | [[Image:Fields outside benambra.jpg|thumb|300px|Fields outside [[Benambra, Victoria]], [[Australia]] suffering from drought conditions.]] | ||
| − | A '''drought''' is an extended period of months or years when a region notes a deficiency in its water supply. Generally, this occurs when a region receives consistently below average [[precipitation (meteorology)|precipitation]]. It can have a substantial impact on the [[ecosystem]] and [[agriculture]] of the affected region. Although droughts can persist for several years, even a short, intense drought can cause significant damage <ref>http://www.bom.gov.au/climate/drought/livedrought.shtml</ref> and harm the local [[economy]]<ref>[http://www.lilith-ezine.com/articles/environmental/Australian-Drought.html Australian Drought and Climate Change], | + | A '''drought''' is an extended period of months or years when a region notes a deficiency in its water supply. Generally, this occurs when a region receives consistently below average [[precipitation (meteorology)|precipitation]]. It can have a substantial impact on the [[ecosystem]] and [[agriculture]] of the affected region. Although droughts can persist for several years, even a short, intense drought can cause significant damage <ref>[http://www.bom.gov.au/climate/drought/livedrought.shtml Living With Drought]. Australian Bureau of Meteorology. Retrieved December 1, 2007.</ref> and harm the local [[economy]]<ref>[http://www.lilith-ezine.com/articles/environmental/Australian-Drought.html Australian Drought and Climate Change]. Lilith Gallery of Toronto. Retrieved December 1, 2007.</ref>. |
==Implications== | ==Implications== | ||
| − | Drought is a normal, recurring feature of the climate in most parts of the world. Having adequate drought mitigation strategies in place can greatly reduce the impact. Recurring or long-term drought can bring about [[desertification]]. Recurring droughts in the [[Horn of Africa]] have created grave [[ecological]] [[catastrophe]]s, prompting massive [[1984 - 1985 famine in Ethiopia|food shortages]], [[2006 Horn of Africa food crisis|still recurring]]. To the north-west of the Horn, the [[Darfur conflict]] in neighboring [[Sudan]], also affecting [[Chad]], was fueled by decades of drought; combination of drought, desertification and [[overpopulation]] are among the causes of the Darfur conflict, because the [[Arab]] [[Baggara]] [[nomads]] searching for water have to take their livestock further south, to land mainly occupied by non-Arab farming peoples.<ref>[http://www.alertnet.org/db/blogs/1265/2007/06/30-100806-1.htm Looking to water to find peace in Darfur]</ref> | + | Drought is a normal, recurring feature of the climate in most parts of the world. Having adequate drought mitigation strategies in place can greatly reduce the impact. Recurring or long-term drought can bring about [[desertification]]. Recurring droughts in the [[Horn of Africa]] have created grave [[ecological]] [[catastrophe]]s, prompting massive [[1984 - 1985 famine in Ethiopia|food shortages]], [[2006 Horn of Africa food crisis|still recurring]]. To the north-west of the Horn, the [[Darfur conflict]] in neighboring [[Sudan]], also affecting [[Chad]], was fueled by decades of drought; combination of drought, desertification and [[overpopulation]] are among the causes of the Darfur conflict, because the [[Arab]] [[Baggara]] [[nomads]] searching for water have to take their livestock further south, to land mainly occupied by non-Arab farming peoples.<ref>[http://www.alertnet.org/db/blogs/1265/2007/06/30-100806-1.htm Looking to water to find peace in Darfur]. Reuters. Retrieved December 1, 2007.</ref> |
| − | According to a UN climate report, the [[Himalayas|Himalayan]] glaciers that are the sources of [[Asia]]'s biggest rivers - [[Ganges]], [[Indus]], [[Brahmaputra]], [[Yangtze]], [[Mekong]], [[Salween]] and [[Yellow River|Yellow]] - could disappear by 2035 as temperatures rise.<ref>[http://www.planetark.com/dailynewsstory.cfm/newsid/42387/story.htm Vanishing Himalayan Glaciers Threaten a Billion]</ref> Approximately 2.4 billion people live in the [[drainage basin]] of the Himalayan rivers.<ref>[http://www.peopleandplanet.net/pdoc.php?id=3024 Big melt threatens millions, says UN]</ref> [[India]], [[China]], [[Pakistan]], [[Bangladesh]], [[Nepal]] and [[Myanmar]] could experience floods followed by droughts in coming decades. [[Drought in India]] affecting the Ganges is of particular concern, as it provides [[drinking water]] and agricultural [[irrigation]] for more than 500 million people.<ref>[http://www.rediff.com/news/2007/jul/24indus.htm Ganges, Indus may not survive: climatologists] | + | According to a UN climate report, the [[Himalayas|Himalayan]] glaciers that are the sources of [[Asia]]'s biggest rivers - [[Ganges]], [[Indus]], [[Brahmaputra]], [[Yangtze]], [[Mekong]], [[Salween]] and [[Yellow River|Yellow]] - could disappear by 2035 as temperatures rise.<ref>[http://www.planetark.com/dailynewsstory.cfm/newsid/42387/story.htm Vanishing Himalayan Glaciers Threaten a Billion]. Planet Ark. Retrieved December 1, 2007.</ref> Approximately 2.4 billion people live in the [[drainage basin]] of the Himalayan rivers.<ref>[http://www.peopleandplanet.net/pdoc.php?id=3024 Big melt threatens millions, says UN]. People and the Planet. Retrieved December 1, 2007.</ref> [[India]], [[China]], [[Pakistan]], [[Bangladesh]], [[Nepal]] and [[Myanmar]] could experience floods followed by droughts in coming decades. [[Drought in India]] affecting the Ganges is of particular concern, as it provides [[drinking water]] and agricultural [[irrigation]] for more than 500 million people.<ref>[http://www.rediff.com/news/2007/jul/24indus.htm Ganges, Indus may not survive: climatologists]. Rediff India Abroad. Retrieved December 1, 2007.</ref> Paradoxically, some proposed [[solar shade|short-term solutions]] [[Mitigation of global warming|to global warming]] also carry with them increased chances of drought.<ref name=NewScientist>Brahic, Catherine. 2007. [http://environment.newscientist.com/article/dn12397-sunshade-for-global-warming-could-cause-drought.html Sunshade' for global warming could cause drought]. New Scientist. Retrieved December 1, 2007.</ref> |
| − | In 2005, parts of the [[Amazon basin]] experienced the worst drought in 100 years.<ref>[http://www.ens-newswire.com/ens/oct2005/2005-10-24-05.asp Environmental News Service - Amazon Drought Worst in 100 Years] | + | In 2005, parts of the [[Amazon basin]] experienced the worst drought in 100 years.<ref>[http://www.ens-newswire.com/ens/oct2005/2005-10-24-05.asp Environmental News Service - Amazon Drought Worst in 100 Years]. Environment News Service. Retrieved December 1, 2007.</ref> A 23 July 2006 article reported [[Woods Hole Research Center]] results showing that the forest in its present form could survive only three years of drought.<ref>[http://news.independent.co.uk/environment/article1191932.ece Amazon rainforest 'could become a desert']. The Independent. Retrieved December 1, 2007.</ref> Scientists at the Brazilian [[National Institute of Amazonian Research]] argue in the article that this drought response, coupled with the effects of [[deforestation]] on regional climate, are pushing the rainforest towards a "[[tipping point]]" where it would irreversibly start to die. It concludes that the [[rainforest]] is on the brink of being turned into [[savanna]] or [[desert]], with catastrophic consequences for the world's climate. According to the [[World Wide Fund for Nature|WWF]], the combination of [[climate change]] and deforestation increases the drying effect of dead trees that fuels forests fires.<ref>[http://www.panda.org/news_facts/newsroom/index.cfm?uNewsID=64220 Climate change a threat to Amazon rainforest, warns WWF]. World Wide Fund for Nature. Retrieved December 1, 2007.</ref> |
==Causes== | ==Causes== | ||
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[[Image:Aralship2.jpg|thumb|Ship stranded by the retreat of the [[Aral Sea]]]] | [[Image:Aralship2.jpg|thumb|Ship stranded by the retreat of the [[Aral Sea]]]] | ||
| − | As a drought persists, the conditions surrounding it gradually worsen and its impact on the local population gradually increases. Droughts go through three stages before their ultimate cessation <ref>http://www.nws.noaa.gov/om/brochures/climate/Drought.pdf [[NOAA]] | + | As a drought persists, the conditions surrounding it gradually worsen and its impact on the local population gradually increases. Droughts go through three stages before their ultimate cessation <ref>[http://www.nws.noaa.gov/om/brochures/climate/Drought.pdf NOAA Fact Sheet]. [[NOAA]]. Retrieved December 1, 2007.</ref>: |
#[[Meteorology|Meteorological]] drought is brought about when there is a prolonged period with less than average precipitation. Meteorological drought usually precedes the other kinds of drought. | #[[Meteorology|Meteorological]] drought is brought about when there is a prolonged period with less than average precipitation. Meteorological drought usually precedes the other kinds of drought. | ||
#[[Agriculture|Agricultural]] droughts are droughts that affect crop production or the ecology of the [[Range (biology)|range]]. This condition can also arise independently from any change in precipitation levels when [[soil]] conditions and erosion triggered by poorly planned agricultural endeavors cause a shortfall in water available to the crops. However, in a traditional drought, it is caused by an extended period of below average precipitation. | #[[Agriculture|Agricultural]] droughts are droughts that affect crop production or the ecology of the [[Range (biology)|range]]. This condition can also arise independently from any change in precipitation levels when [[soil]] conditions and erosion triggered by poorly planned agricultural endeavors cause a shortfall in water available to the crops. However, in a traditional drought, it is caused by an extended period of below average precipitation. | ||
| − | #[[Hydrology|Hydrological]] drought is brought about when the [[water reserve]]s available in sources such as [[aquifer]]s, [[lake]]s and [[reservoir]]s falls below the [[statistical]] [[average]]. Like an agricultural drought, this can be triggered by more than just a loss of rainfall. For instance, [[Kazakhstan]] was recently awarded a large amount of money by the [[World Bank]] to restore water that had been diverted to other nations from the [[Aral Sea]] under [[Soviet]] rule <ref>http://news.bbc.co.uk/2/hi/asia-pacific/6538219.stm | + | #[[Hydrology|Hydrological]] drought is brought about when the [[water reserve]]s available in sources such as [[aquifer]]s, [[lake]]s and [[reservoir]]s falls below the [[statistical]] [[average]]. Like an agricultural drought, this can be triggered by more than just a loss of rainfall. For instance, [[Kazakhstan]] was recently awarded a large amount of money by the [[World Bank]] to restore water that had been diverted to other nations from the [[Aral Sea]] under [[Soviet]] rule <ref>[http://news.bbc.co.uk/2/hi/asia-pacific/6538219.stm Dam project aims to save Aral Sea]. BBC News. Retrieved December 1, 2007.</ref>. Similar circumstances also place their largest lake, [[Balkhash]], at risk of completely drying out. <ref>[http://news.bbc.co.uk/2/hi/asia-pacific/3397077.stm Kazakh lake 'could dry up']. BBC News. Retrieved December 1, 2007. |
| + | </ref> | ||
== Consequences == | == Consequences == | ||
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* Death of [[livestock]]. | * Death of [[livestock]]. | ||
* Reduced [[crop yield]]s. | * Reduced [[crop yield]]s. | ||
| − | * [[Wildfires]], such as [[Australia]]n [[bushfire]]s, are more common during times of drought. | + | * [[Wildfires]], such as [[Australia]]n [[bushfire]]s, are more common during times of drought. |
| − | * Shortages of water for [[industry|industrial]] users. <ref>http://www.sfgate.com/cgi-bin/article.cgi?file=/c/a/2005/03/06/MNGE2BL7161.DTL Parched village sues to shut tap at Coke | + | * Shortages of water for [[industry|industrial]] users. <ref>[http://www.sfgate.com/cgi-bin/article.cgi?file=/c/a/2005/03/06/MNGE2BL7161.DTL Parched village sues to shut tap at Coke]. San Francisco Chronicle. Retrieved December 1, 2007.</ref> |
* [[Desertification]] | * [[Desertification]] | ||
* [[Dust storms]], when drought hits an area suffering from desertification and [[erosion]] | * [[Dust storms]], when drought hits an area suffering from desertification and [[erosion]] | ||
| Line 44: | Line 45: | ||
* [[War]] over natural resources, including water and food. | * [[War]] over natural resources, including water and food. | ||
* Reduced electricity production due to insufficient available coolant | * Reduced electricity production due to insufficient available coolant | ||
| − | * [[Snakes]] have been known to emerge and snakebites become more common.<ref>http://news.bbc.co.uk/2/hi/asia-pacific/6282075.stm Australians Face Snake Invasion. | + | * [[Snakes]] have been known to emerge and snakebites become more common.<ref>[http://news.bbc.co.uk/2/hi/asia-pacific/6282075.stm Australians Face Snake Invasion]. BBC News. Retrieved December 1, 2007.</ref> |
The effect varies according to vulnerability. For example, subsistence farmers are more likely to migrate during drought because they do not have alternative food sources. Areas with populations that depend on [[subsistence farming]] as a major food source are more vulnerable to drought-triggered famine. Drought is rarely if ever the sole cause of famine; socio-political factors such as extreme widespread poverty play a major role. Drought can also reduce water quality, because lower water flows reduce dilution of pollutants and increase [[contamination]] of remaining water sources. | The effect varies according to vulnerability. For example, subsistence farmers are more likely to migrate during drought because they do not have alternative food sources. Areas with populations that depend on [[subsistence farming]] as a major food source are more vulnerable to drought-triggered famine. Drought is rarely if ever the sole cause of famine; socio-political factors such as extreme widespread poverty play a major role. Drought can also reduce water quality, because lower water flows reduce dilution of pollutants and increase [[contamination]] of remaining water sources. | ||
| Line 50: | Line 51: | ||
==Drought mitigation strategies== | ==Drought mitigation strategies== | ||
* [[Desalination]] of sea water for irrigation or consumption. | * [[Desalination]] of sea water for irrigation or consumption. | ||
| − | * Drought monitoring - Continuous observation of rainfall levels and comparisons with current usage levels can help prevent man-made drought. For instance, analysis of water usage in [[Yemen]] has revealed that their [[water table]] (underground water level) is put at grave risk by over-use to fertilize their [[Khat]] crop. <ref>http://news.bbc.co.uk/2/hi/programmes/from_our_own_correspondent/6530453.stm | + | * Drought monitoring - Continuous observation of rainfall levels and comparisons with current usage levels can help prevent man-made drought. For instance, analysis of water usage in [[Yemen]] has revealed that their [[water table]] (underground water level) is put at grave risk by over-use to fertilize their [[Khat]] crop. <ref>[http://news.bbc.co.uk/2/hi/programmes/from_our_own_correspondent/6530453.stm Yemen's khat habit soaks up water]. BBC News. Retrieved December 1, 2007.</ref> Careful monitoring of moisture levels can also help predict increased risk for wildfires, using such metrics as the [[Keetch-Byram Drought Index]] or [[Palmer Drought Index]]. |
* Land use - Carefully planned [[crop rotation]] can help to minimize [[erosion]] and allow farmers to plant less water-dependent crops in drier years. | * Land use - Carefully planned [[crop rotation]] can help to minimize [[erosion]] and allow farmers to plant less water-dependent crops in drier years. | ||
* [[Rainwater harvesting]] - Collection and storage of rainwater from roofs or other suitable catchments. | * [[Rainwater harvesting]] - Collection and storage of rainwater from roofs or other suitable catchments. | ||
| Line 56: | Line 57: | ||
* [[Transvasement]] - Building canals or redirecting rivers as massive attempts at [[irrigation]] in drought-prone areas. | * [[Transvasement]] - Building canals or redirecting rivers as massive attempts at [[irrigation]] in drought-prone areas. | ||
* [[Water restrictions]] - Water use may be regulated (particularly outdoors). This may involve regulating the use of sprinklers, hoses or buckets on outdoor plants, the washing of motor vehicles or other outdoor hard surfaces (including roofs and paths), topping up of swimming pools, and also the fitting of water conservation devices inside the home (including shower heads, taps and dual flush toilets). | * [[Water restrictions]] - Water use may be regulated (particularly outdoors). This may involve regulating the use of sprinklers, hoses or buckets on outdoor plants, the washing of motor vehicles or other outdoor hard surfaces (including roofs and paths), topping up of swimming pools, and also the fitting of water conservation devices inside the home (including shower heads, taps and dual flush toilets). | ||
| − | * [[Cloud seeding]] - an artificial technique to induce rainfall. <ref>http://www.chinadaily.com.cn/english/doc/2004-07/24/content_351196.htm</ref> | + | * [[Cloud seeding]] - an artificial technique to induce rainfall. <ref>[http://www.chinadaily.com.cn/english/doc/2004-07/24/content_351196.htm Cloud seeding helps alleviate drought]. China Daily. Retrieved December 1, 2007.</ref> |
== See also == | == See also == | ||
Revision as of 19:58, 1 December 2007
Fields outside Benambra, Victoria, Australia suffering from drought conditions.
A drought is an extended period of months or years when a region notes a deficiency in its water supply. Generally, this occurs when a region receives consistently below average precipitation. It can have a substantial impact on the ecosystem and agriculture of the affected region. Although droughts can persist for several years, even a short, intense drought can cause significant damage [1] and harm the local economy[2].
Implications
Drought is a normal, recurring feature of the climate in most parts of the world. Having adequate drought mitigation strategies in place can greatly reduce the impact. Recurring or long-term drought can bring about desertification. Recurring droughts in the Horn of Africa have created grave ecological catastrophes, prompting massive food shortages, still recurring. To the north-west of the Horn, the Darfur conflict in neighboring Sudan, also affecting Chad, was fueled by decades of drought; combination of drought, desertification and overpopulation are among the causes of the Darfur conflict, because the Arab Baggara nomads searching for water have to take their livestock further south, to land mainly occupied by non-Arab farming peoples.[3]
According to a UN climate report, the Himalayan glaciers that are the sources of Asia's biggest rivers - Ganges, Indus, Brahmaputra, Yangtze, Mekong, Salween and Yellow - could disappear by 2035 as temperatures rise.[4] Approximately 2.4 billion people live in the drainage basin of the Himalayan rivers.[5] India, China, Pakistan, Bangladesh, Nepal and Myanmar could experience floods followed by droughts in coming decades. Drought in India affecting the Ganges is of particular concern, as it provides drinking water and agricultural irrigation for more than 500 million people.[6] Paradoxically, some proposed short-term solutions to global warming also carry with them increased chances of drought.[7]
In 2005, parts of the Amazon basin experienced the worst drought in 100 years.[8] A 23 July 2006 article reported Woods Hole Research Center results showing that the forest in its present form could survive only three years of drought.[9] Scientists at the Brazilian National Institute of Amazonian Research argue in the article that this drought response, coupled with the effects of deforestation on regional climate, are pushing the rainforest towards a "tipping point" where it would irreversibly start to die. It concludes that the rainforest is on the brink of being turned into savanna or desert, with catastrophic consequences for the world's climate. According to the WWF, the combination of climate change and deforestation increases the drying effect of dead trees that fuels forests fires.[10]
Causes
Generally, rainfall is related to the amount of water vapor in the atmosphere, combined with the upward forcing of the air mass containing that water vapor. If either of these is reduced, the result is drought.
Factors include:
- Above-average prevalence of high pressure systems.
- Winds carrying continental, rather than oceanic air masses (ie. reduced water content).
- El Nino (and other oceanic temperature cycles).
- Deforestation.
Stages of drought
Ship stranded by the retreat of the Aral Sea
As a drought persists, the conditions surrounding it gradually worsen and its impact on the local population gradually increases. Droughts go through three stages before their ultimate cessation [11]:
- Meteorological drought is brought about when there is a prolonged period with less than average precipitation. Meteorological drought usually precedes the other kinds of drought.
- Agricultural droughts are droughts that affect crop production or the ecology of the range. This condition can also arise independently from any change in precipitation levels when soil conditions and erosion triggered by poorly planned agricultural endeavors cause a shortfall in water available to the crops. However, in a traditional drought, it is caused by an extended period of below average precipitation.
- Hydrological drought is brought about when the water reserves available in sources such as aquifers, lakes and reservoirs falls below the statistical average. Like an agricultural drought, this can be triggered by more than just a loss of rainfall. For instance, Kazakhstan was recently awarded a large amount of money by the World Bank to restore water that had been diverted to other nations from the Aral Sea under Soviet rule [12]. Similar circumstances also place their largest lake, Balkhash, at risk of completely drying out. [13]
Consequences
Periods of drought can have significant environmental, economic and social consequences. The most common consequences include:
- Death of livestock.
- Reduced crop yields.
- Wildfires, such as Australian bushfires, are more common during times of drought.
- Shortages of water for industrial users. [14]
- Desertification
- Dust storms, when drought hits an area suffering from desertification and erosion
- Malnutrition, dehydration and related diseases.
- Famine due to lack of water for irrigation.
- Social unrest.
- Mass migration, resulting in internal displacement and international refugees.
- War over natural resources, including water and food.
- Reduced electricity production due to insufficient available coolant
- Snakes have been known to emerge and snakebites become more common.[15]
The effect varies according to vulnerability. For example, subsistence farmers are more likely to migrate during drought because they do not have alternative food sources. Areas with populations that depend on subsistence farming as a major food source are more vulnerable to drought-triggered famine. Drought is rarely if ever the sole cause of famine; socio-political factors such as extreme widespread poverty play a major role. Drought can also reduce water quality, because lower water flows reduce dilution of pollutants and increase contamination of remaining water sources.
Drought mitigation strategies
- Desalination of sea water for irrigation or consumption.
- Drought monitoring - Continuous observation of rainfall levels and comparisons with current usage levels can help prevent man-made drought. For instance, analysis of water usage in Yemen has revealed that their water table (underground water level) is put at grave risk by over-use to fertilize their Khat crop. [16] Careful monitoring of moisture levels can also help predict increased risk for wildfires, using such metrics as the Keetch-Byram Drought Index or Palmer Drought Index.
- Land use - Carefully planned crop rotation can help to minimize erosion and allow farmers to plant less water-dependent crops in drier years.
- Rainwater harvesting - Collection and storage of rainwater from roofs or other suitable catchments.
- Recycled water - Former wastewater (sewage) that has been treated and purified for reuse.
- Transvasement - Building canals or redirecting rivers as massive attempts at irrigation in drought-prone areas.
- Water restrictions - Water use may be regulated (particularly outdoors). This may involve regulating the use of sprinklers, hoses or buckets on outdoor plants, the washing of motor vehicles or other outdoor hard surfaces (including roofs and paths), topping up of swimming pools, and also the fitting of water conservation devices inside the home (including shower heads, taps and dual flush toilets).
- Cloud seeding - an artificial technique to induce rainfall. [17]
See also
Notes
- ↑ Living With Drought. Australian Bureau of Meteorology. Retrieved December 1, 2007.
- ↑ Australian Drought and Climate Change. Lilith Gallery of Toronto. Retrieved December 1, 2007.
- ↑ Looking to water to find peace in Darfur. Reuters. Retrieved December 1, 2007.
- ↑ Vanishing Himalayan Glaciers Threaten a Billion. Planet Ark. Retrieved December 1, 2007.
- ↑ Big melt threatens millions, says UN. People and the Planet. Retrieved December 1, 2007.
- ↑ Ganges, Indus may not survive: climatologists. Rediff India Abroad. Retrieved December 1, 2007.
- ↑ Brahic, Catherine. 2007. Sunshade' for global warming could cause drought. New Scientist. Retrieved December 1, 2007.
- ↑ Environmental News Service - Amazon Drought Worst in 100 Years. Environment News Service. Retrieved December 1, 2007.
- ↑ Amazon rainforest 'could become a desert'. The Independent. Retrieved December 1, 2007.
- ↑ Climate change a threat to Amazon rainforest, warns WWF. World Wide Fund for Nature. Retrieved December 1, 2007.
- ↑ NOAA Fact Sheet. NOAA. Retrieved December 1, 2007.
- ↑ Dam project aims to save Aral Sea. BBC News. Retrieved December 1, 2007.
- ↑ Kazakh lake 'could dry up'. BBC News. Retrieved December 1, 2007.
- ↑ Parched village sues to shut tap at Coke. San Francisco Chronicle. Retrieved December 1, 2007.
- ↑ Australians Face Snake Invasion. BBC News. Retrieved December 1, 2007.
- ↑ Yemen's khat habit soaks up water. BBC News. Retrieved December 1, 2007.
- ↑ Cloud seeding helps alleviate drought. China Daily. Retrieved December 1, 2007.
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