Natural Disaster || Drought
A drought in a given area is a period of below-average rainfall, resulting in a prolonged decrease in its water supply, whether atmospheric, surface water, or groundwater. The drought can last for months or years, or can be declared after 15 days. This can have a substantial impact on the ecosystem and agriculture of the affected area and harm the local economy. The dry weather in the tropics in the tropics increases the potential for drought development and subsequent fire. The summer period can significantly worsen drought conditions by accelerating the evaporation of water vapor.
Many plant species, such as the family Cactacea (or Cacti), have drought tolerance adaptation, such as low leaf area and waxy cuticles to increase their ability to tolerate drought. Some other dried seeds survive as buried seeds. The semi-permanent drought produces dry biomes such as deserts and grasslands. Prolonged drought has led to mass migration and humanitarian crises. Most arid ecosystems have inherently low productivity. The longest drought in the world in recorded history occurred in the Atacama Desert in Chile (400 years).
Causes of drought
Precipitation deficiency
Ancient Meso-American civilizations may have amplified droughts by deforestation.
Mechanisms of productive precipitation include convection, straightform, and organic rainfall. Sensory processes include strong vertical motions that can cause the atmosphere to reverberate in that location within an hour and cause heavy rainfall, while stratiform processes include weak upward movements and less intense precipitation over long periods is. Redevelopment can be divided into three categories, based on whether it falls as liquid water, liquid water that freezes on contact with the surface, or ice. Drought is mainly in areas with low rainfall. If these factors do not support sufficient amount of rainfall to reach the surface in sufficient time, the result is dry. Drought can be triggered by higher-than-average sunlight and higher-than-average propagation of high-pressure systems, which pick up continental winds rather than oceanic winds, and streaks of high-pressure areas with thunderstorm activity or rain May inhibit or prevent the development of. Certain area. Once an area is within a drought, the local dry air, the reaction mechanism due to hot conditions that can promote the warm core, and minimal evaporation can worsen the drought conditions.
Dry season
Within the tropical zone, the differential, tropical erosion zone or circulation of the monsoon trough produces distinct, wet and dry seasons. The dry season greatly increases the dry season, and is characterized by low humidity, in which water pores and rivers dry up. Due to the lack of these water holes, many grazing animals are forced to migrate due to lack of water and feed more fertile places. Examples of such animals are zebra, elephant and wildebeest. Due to lack of water in the plants, shrubs are common. As the water vapor becomes more energetic with increasing temperature, more water vapor is required to raise the values with higher humidity to 100% at higher temperatures (or to obtain a temperature to fall at the dew point). The summer period accelerates fruit and vegetable production, increases evaporation and transpiration from plants, and worsens drought conditions.
El Niñ
During the El Niño events there is a dry and warm season in the Amazon River Basin, Colombia, and parts of Central America. Winters during El Niño are warmer and drier than average conditions in the northwest, northern Midwest, and northern Mid-East United States, so those areas experience less snowfall. In South-Central Africa, mainly in Zambia, Zimbabwe, Mozambique and Botswana, conditions are drier than usual from December to February. The direct influence of El Niño has led to drizzle in parts of Southeast Asia and northern Australia, causing bush fires, increasing haze and dramatically decreasing air quality. From June to August a more normal-than-normal condition is observed in Queensland, inland Victoria, inland New South Wales and East Tasmania. Since warm water spreads from the West Pacific and the Indian Ocean to the East Pacific, it causes widespread drought in the Western Pacific. Singapore experienced a drought in February in 2014 as the record began in 1869, with only 6.3 mm of rain a month and temperatures reaching 35 ° C on 26 February. The years of 1968 and 2005 were the next drought years, with 8.4 mm of rainfall.
Erosion and human activities
Fires on Borneo and Sumatra, 2006. People use slash-and-burndeforestation to clear land for agriculture.
Human activity can directly trigger exacerbating factors such as over farming, excessive irrigation, deforestation, and erosion adversely impact the ability of the land to capture and hold water. In arid climates, the main source of erosion is wind. Erosion can be the result of material movement by the wind. The wind can cause small particles to be lifted and therefore moved to another region (deflation). Suspended particles within the wind may impact on solid objects causing erosion by abrasion (ecological succession). Wind erosion generally occurs in areas with little or no vegetation, often in areas where there is insufficient rainfall to support vegetation.
Loess is a homogeneous, typically nonstratified, porous, friable, slightly coherent, often calcareous, fine-grained, silty, pale yellow or buff, windblown (Aeolian) sediment. It generally occurs as a widespread blanket deposit that covers areas of hundreds of square kilometers and tens of meters thick. Loess often stands in either steep or vertical faces. Loess tends to develop into highly rich soils. Under appropriate climatic conditions, areas with loess are among the most agriculturally productive in the world. Loess deposits are geologically unstable by nature, and will erode very readily. Therefore, windbreaks (such as big trees and bushes) are often planted by farmers to reduce the wind erosion of loess. Wind erosion is much more severe in arid areas and during times of drought. For example, in the Great Plains, it is estimated that soil loss due to wind erosion can be as much as 6100 times greater in drought years than in wet years.
Climate change
Activities that occur as a result of global climate change are expected to trigger droughts with substantial impacts on agriculture worldwide and especially in developing countries. Overall, global warming will result in increased rainfall in the world. With drought in some areas, flooding and erosion will increase in others. Paradoxically, some proposed solutions to global warming that focus on more active technologies, solar radiation management through the use of a space canopy for one, may increase the likelihood of drought.
Types
As a drought persists, the conditions surrounding it gradually worsen and its impact on the local population gradually increases. People tend to define droughts in three main ways:
1. Meteorological drought is brought about when there is a prolonged time with less than average precipitation. Meteorological drought usually precedes the other kinds of drought.
2. 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.
3. Hydrological drought is brought about when the water reserves available in sources such as aquifers, lakes and reservoirs fall below the statistical average. Hydrological drought tends to show up more slowly because it involves stored water that is used but not replenished. 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.Similar circumstances also place their largest lake, Balkhash, at risk of completely drying out.
Consequences of drought
The effects of droughts and water shortages can be divided into three groups: environmental, economic and social consequences. In the case of environmental effects: lower surface and subterranean water levels, lower flow levels (with a decrease below the minimum leading to direct danger for amphibian life), increased pollution of surface water, the drying out of wetlands, more and larger fires, higher deflation intensity, losing biodiversity, worse health of trees and the appearance of pests and den droid diseases. Economic losses include lower agricultural, forest, game and fishing output, higher food production costs, lower energy production levels in hydro plants, losses caused by depleted water tourism and transport revenue, problems with water supply for the energy sector and technological processes in metallurgy, mining, the chemical, paper, wood, foodstuff industries etc., disruption of water supplies for municipal economies. Meanwhile, social costs include the negative effect on the health of people directly exposed to this phenomenon (excessive heat waves), possible limitation of water supplies and its increased pollution levels, high food costs, stress caused by failed harvests, etc. This is why droughts and fresh water shortages may be considered as a factor which increases the gap between developed and developing countries.
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 water sources as a major food source are more vulnerable to famine.
Drought can also reduce water quality,because lower water flows reduce dilution of pollutants and increase contamination of remaining water sources. Common consequences of drought include:
· Wildfires, such as Australian bushfires, are more common during times of drought and even death of people.
· Cyanotoxin accumulation within food chains and water supply, some of which are among the most potent toxins known to science, can cause cancer with low exposure over long term. High levels of microcystin has been found in San Francisco Bay Area salt water shellfish and fresh water supplies throughout the state of California in 2016.
Globally
Drought is a normal, recurring feature of the climate in most parts of the world. It is among the earliest documented climatic events, present in the Epic of Gilgamesh and tied to the biblical story of Joseph's arrival in and the later Exodus from Ancient Egypt. Hunter-gatherer migrations in 9,500 BC Chile have been linked to the phenomenon, as has the exodus of early humans out of Africa and into the rest of the world around 135,000 years ago.
Examples
Well-known historical droughts include:
· 1900 India killing between 250,000 and 3.25 million.
· 1921–22 Soviet Union in which over 5 million perished from starvation due to drought
· 1928–30 Northwest China resulting in over 3 million deaths by famine.
· 1936 and 1941 Sichuan Province China resulting in 5 million and 2.5 million deaths respectively.
· The 1997–2009 Millennium Drought in Australia led to a water supply crisis across much of the country. As a result, many desalination plants were built for the first time .
· In 2006, Sichuan Province China experienced its worst drought in modern times with nearly 8 million people and over 7 million cattle facing water shortages.
· 12-year drought that was devastating southwest Western Australia, southeast South Australia, Victoria and northern Tasmania was "very severe and without historical precedent".
The Darfur conflict in 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 people.
Approximately 2.4 billion people live in the drainage basin of the Himalayan rivers.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. The west coast of North America, which gets much of its water from glaciers in mountain ranges such as the Rocky Mountains and Sierra Nevada, also would be affected.
In 2005, parts of the Amazon basin experienced the worst drought in 100 years. 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. Scientists at the Brazilian National Institute of Amazonian Research argue in the article that this drought response, coupled with the effects of deforestationon 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 forest fires.
By far the largest part of Australia is desert or semi-arid land commonly known as the outback. A 2005 study by Australian and American researchers examined desertification of the interior, and suggested that one explanation was related to human settlers who arrived about 50,000 years ago. Regular burns by these settlements could have prevented the monsoon from reaching inner Australia. In June 2008 it became known that an expert panel had warned for a long, perhaps irreversible, serious ecological damage to the entire Morena-Darling Basin if it did not receive enough water by October 2008. Australia may experience more severe droughts and they may become more frequent in the future, a government commission report said on 6 July 2008. Australian environmentalist Tim Flannery predicted that Perth could become the world's first ghost metropolis in Western Australia, an abandoned city without water, until it undergoes major changes. To maintain its population. The long Australian Millennial drought broke out in 2010.
The drought leading to desertification in East Africa has caused severe ecological catastrophe, leading to food shortages in 1984–85, 2006 and 2011. During the 2011 drought, an estimated 50,000 to 150,000 people died, although these figures and extent to which the crisis occurred are disputed. In February 2012, the United Nations announced that the crisis was over due to relief efforts and scaling of a plentiful crop. Aid agencies later shifted their emphasis to recovery efforts, including digging irrigation canals and distributing seed of plants.
In 2012, the Western Sahel suffered a severe drought. The Methodist Relief and Development Fund (MRDF) reported that more than 10 million people in the region were at risk of famine due to a month-long heat wave that hit the Niger, Mali, Mauritania and Burkina fekos. Funds of around £ 20,000 were disbursed to drought-stricken countries.
Protection, mitigation and relief
Succulent plants are well-adapted to survive long periods of drought.
Agriculturally, people can effectively mitigate much of the impact of drought through irrigation and crop rotation. Failure to develop adequate drought mitigation strategies carries a grave human cost in the modern era, exacerbated by ever-increasing population densities. President Roosevelt on April 27, 1935, signed documents creating the Soil Conservation Service (SCS)—now the Natural Resources Conservation Service (NRCS). Models of the law were sent to each state where they were enacted. These were the first enduring practical programs to curtail future susceptibility to drought, creating agencies that first began to stress soil conservation measures to protect farm lands today. It was not until the 1950s that there was an importance placed on water conservation was put into the existing laws (NRCS 2014).
Aerosols over the Amazon each September for four burning seasons (2005 through 2008) during the Amazon basin drought. The aerosol scale (yellow to dark reddish-brown) indicates the relative amount of particles that absorb sunlight.
Strategies for drought protection, mitigation or relief include:
· Cloud seeding - a form of intentional weather modification to induce rainfall.This remains a hotly debated topic, as the United States National Research Council released a report in 2004 stating that to date, there is still no convincing scientific proof of the efficacy of intentional weather modification.
· 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.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.
· Outdoor water-use restriction - Regulating the use of sprinklers, hoses or buckets on outdoor plants, filling pools, and other water-intensive home maintenance tasks. Xeriscaping yards can significantly reduce unnecessary water use by residents of towns and cities.
· Rainwater harvesting - Collection and storage of rainwater from roofs or other suitable catchments.
· Transvasement - Building canals or redirecting rivers as massive attempts at irrigation in drought-prone areas.
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