Drought

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 and harm the local economy According to the UN, an area of fertile soil the size of Ukraine is lost every year because of drought, deforestation and climate instability.

Implications

Lake Chad in a 2001 satellite image, with the actual lake in blue. The lake has shrunk by 95% since the 1960s.

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. 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 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 forest fires. Paradoxically, some proposed short-term solutions to global warming also carry with them increased chances of drought.

Causes

Generally, rainfall is related to the amount of water vapour in the atmosphere, combined with the upward forcing of the air mass containing that water vapour. If either of these are reduced,the result is a drought. Factors include:

• Above average prevalence of high pressure systems;
• Winds carrying continental, rather than oceanic air masses (ie. reduced water content);
• Ridges of high pressure areas form with behaviors which prevent or restrict the developing of thunderstorm activity or rainfall over one certain region;
• El Nino, La Nina (and other oceanic and atmospheric temperature cycles) and global warming;
• Deforestation and erosion adversly impacting the ability of the land to capture water;
• Climate change has a substantial impact on agriculture throughout the world, and especially in developing nations.

Consequences

Dry earth in the Sonora desert, Mexico.

Periods of drought can have significant environmental, agricultural, health, economic and social consequences. Examples 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.
• 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.
• Substandard or highly limited crop growth or yield productions.
• 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 for power stations and reduced water flow through hydroelectric dams.
• Snakes have been known to emerge and snakebites become more common.
• Creates windblown dust bowls which erodes the landscape, damages terrestrial and aquatic wildlife habitat

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.

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:

1. 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.
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 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. Similar circumstances also place their largest lake, Balkhash, at risk of completely drying out.

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. 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.

US Droughts

The Dust Bowl of the 1930s would be noted for heavy drought across many states. 1934, 1936 and 1939 would be extremely hot and dry years across the United States. Hot temperatures led to many people's, livestock's and animal deaths all over the United States. Hundred-degree temperatures would be very common over the United States; dust storms were common, everyone residing in the United States suffered. Making matters worse, these really damaging days of drought hit during when the Great Depression was affecting economies, families and children over the United States.

The Northeastern United States were hit with devastating drought which lasted almost four or five years in the 1960s. The drought affected multiple regional cities from Virginia into Pennsylvania, New Jersey and New York. And some Midwest States became victims of this notorious drought during the same time as the Northeast United States.

Parallel or matching spells hit the Northeast United States during 1999-the Northeast, including Kentucky, New York, New Jersey, Pennsylvania and Maryland were pummeled by extensive heat waves which killed many people across the Northeastern US and unusually dry conditions caused billions of dollars in destruction during 1999. This unusually damaging drought was reminiscent of the Northeast United States Drought of the 1960s considering it affected similar or matching states within the Northeast United States and New England.

One exceptional and really devastating drought in the United States was during 1988 and 1989. The drought baked multiple regions including the Mid-Atlantic, Southeastern United States, the Midwest, the Northern Great Plains and Western United States. This drought was widespread, unusually intense and accompanied by heat waves which killed around 4,800 to 17,000 people across the United States and also killed many livestock, hens, cattle, horses, farm animals and other animals across the United States. The Drought of 1988 destroyed crops almost nationwide, residents' lawns went brown and water restrictions hit many cities. The Yellowstone National Park fell victim to wildfires that burned many trees and created exceptional destruction in the area.

But wildfires and brush fires were not only in the area of Yellowstone-the same wildfires and brush fires were affecting other states and regional areas all over the United States. The 1988 Drought caused water restrictions in many areas of the country. Residents with grass brown rather than green were common during 1988 and 1989 in widespread areas across the United States.

The Droughts of 1988 caused exceptional damages totaling $60 billion in 1988 United States Dollars and became the costliest weather disaster in recorded weather histories to affect the United States. This drought was very catastrophic for multiple reasons. The drought continued across the Upper Midwest States and North Plains States during 1989, not officially ending until 1990. The US Drought of 1988 had an economic force of impact that still lives on in people's minds.

The conditions continued into 1989 and 1990, although the drought had ended in some states. The drought also affected Canada in certain divisions.

Droughts also eviscerated the Northeast US, Corn Belt and Midwest States during 1980 and 1983. The 1983 Midwestern States Drought was connected with very dry conditions, severe heat and substandard crop growth which affected prices and caused hardship for farmers. Hundred-degree readings became very prevalent in 1983 during these dry spells and exceptional heat waves all over the Midwest, Ohio Valley Regions and Great Lakes. The associating heat waves killed between 500-700 people in the United States.

Other famous drought years in the United States happened through the 1950s.

The Midwest and Rockies became victims during 2002; the regions fell victim under exceptional drought which was accompanied by dry conditions, wildfires and hot temperatures over the Western US and Midwestern State areas.

Although the Western United States and Southwestern US are likeliest, droughts can also happen over Upper Midwestern States, the Central Great Plains, Southeast United States, the Middle Atlantic, the Great Lakes Region, the Ohio River Valley, Northeastern United States and even New England. Droughts vary in severity and have potential for causing elevated to exceptional damage wherever they focus their area toward.

See also

• Maya collapse
• Climate change and agriculture
• Drought in Australia
• Droughts and famines in Russia and USSR
• Food security
• United Nations Convention to Combat Desertification
• Water crisis

External links

• National Integrated Drought Information System
• Social & Economic Costs of Drought from "NOAA Socioeconomics" website initiative
• Water scarcity from FAO Water (Food and Agriculture Organization of the United Nations)