Drought

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Droughtmaster :: Drought

For the term as used in sports, see Drought (sport)

A drought or an extreme dry periodic climate is an extended period where water availability falls below the statistical requirements for a region. Drought is not a purely physical phenomenon, but rather an interplay between natural water availability and human demands for water supply.

Meanings

The precise definition of drought is made complex owing to political considerations, but there are generally three types of conditions that are referred to as drought.

Meteorological drought is brought about when there is a prolonged period with less than average precipitation.
Agricultural drought is brought about when there is insufficient moisture for average crop or range production. This condition can arise, even in times of average precipitation, owing to soil conditions or agricultural techniques.
Hydrological drought is brought about when the water reserves available in sources such as aquifers, lakes, and reservoirs falls below the statistical average. This condition can arise, even in times of average (or above average) precipitation, when increased usage of water diminishes the reserves.

When the word "drought" is used commonly, the most often intended definition is meteorological drought. However, when the word is used by urban planners, it is more frequently in the sense of hydrologic drought.

Causes

In the United States, major drought episodes in the midwest are associated with an amplification of the upper tropospheric monsoon ridge along with a weakening of the western edge of the "Bermuda high" and the low-level jet stream over the great plains.^*.

Consequences

Periods of drought can have significant environmental, economic and social consequences. The most common consequences are:

Wildfires
Migration or relocation of those impacted
Social unrest
War
Famine due to lack of water for irrigation
Disease
Thirst

The causes of these problems are complex and relate to increased dependence on external resources (inability to grow crops locally) and lowered quality (and thus contamination) of remaining water sources among other factors. The quality of national infrastructure can increase or decrease the impact of drought, especially with respect to famine, dramatically.

Famous droughts

18th and 19th centuries, Cape Verde

Three droughts were responsible for over 100,000 starvation deaths. These droughts spurred the migration of much of the population to locations such as New England, to participate in the whaling industry.

1900, India

250,000 to 3.25 million die from drought, starvation and disease.

1921-22, Soviet Union

In the Ukraine and Volga regions, 250,000 to 5 million perished from starvation due to drought.

1932-34, Soviet Union

In the Ukraine, Kuban and North Caucasus regions, 5 to 10 million perish; see also Holodomor.

1928-30, northwest China

Famine results in over 3 million deaths.

1936, Sichuan Province, China

This was the worst drought in the modern history of the area. 34 million farmers were displaced and 5 million people starved.

1930-37, United States

Three waves of drought during this time are collectively referred to as "the Dust Bowl". Because of several factors including the coincidence of the dustbowl and the Great Depression, this drought had a severe impact on the U.S., resulting in entire districts of the American Great Plains being depopulated and people were forced to leave.

1941, Sichuan Province, China

This was less severe than the 1936 drought, and resulted in the deaths of only 2.5 million. However, because of the war with Japan at the time, the indirect damage caused was far more dramatic and more devastating.

1965-67, India

Drought results in over 1.5 million deaths.

1968-74, Sahel

The Sahelian drought that began in 1968 was responsible for the deaths of between 100,000 and 250,000 people, the disruption of millions of lives, and the collapse of the agricultural bases of five countries.

1968-72, Iran

A blizzard ended a four-year drought, but the weeklong cold and snow caused the deaths of approximately 4,000 people.

1973–74, Ethiopia

This fuasd (part of the overall Sahelian drought) resulted in a military coup, which overthrew the government of Haile Selassie.

1982-83, Australia

Associated with a strong El Niño, rainfall in eastern Australia and South Australia (except the north coast of New South Wales) was at record low or near record low levels in every month from July 1982 to February 1983. In the Wimmera, rainfall from April 1982 to February 1983 was less than half the previous record low in 110 years of records.

Wheat yields in Victoria were the lowest since 1944 and in New South Wales since 1957, with many crops failing completely. Dust storms spread all over abandoned farmland and moved huge quantities of scarce topsoil from the Mallee and other grain regions.

1983, Bolivia

Severe and prolonged drought during 1983 that affected large areas of seven of Bolivia's nine departments, an estimated 80 percent of the normal fall harvest of staple crops was lost. Total agricultural losses were estimated at U.S. $417.2 million: $277.7 million in crop losses and $139.5 million in livestock losses. These losses included over 200,000 cattle, 3,000,000 sheep, and 660,000 llamas and alpacas.

1984-85, Ethiopia

The 1984 - 1985 famine in Ethiopia was a direct result of this drought, and lead to another regime change – this time to a Marxist government.

1988, North America

Followed several years of precipitation surplus. Worst drought since 1936 in the Midwest of the United States and the Canadian Prairie Provinces. (Cincinnati, Ohio, however, received sustained, heavy rains.) Fringe effects of the drought, however, were felt across the entire continent.

External links

Hydrology | Droughts | Weather hazards

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