Download Droughts

DROUGHT
Causes
Droughts are caused by a lessening of precipitation over time. Unlike a dry spell,
prolonged lack of rain will cause regions around the world to slowly dry out.
Atmospheric conditions such as climate change, ocean temperatures, changes in
the jet stream, and changes in the local landscape are all culprits in the long story
of the causes of droughts.
Because drought is defined as a deficit in water supply, it can be caused by a
number of factors. The most important one though relates to the amount of water
vapor in the atmosphere as this is what creates precipitation. More rain, sleet, hail,
and snow can occur where there are moist, low pressure air systems. If there is an
above average presence of dry, high pressure air systems instead, less moisture is
available to produce precipitation (because these systems cannot hold as much
water vapor). This results in a deficit of water for the areas over which they move.
The same can also happen when winds shift air masses and warm, dry, continental
air moves over an area as opposed to cooler, moist, oceanic air masses. El Nino,
which affects the ocean's water temperature, also has an impact on precipitation
levels because in years when the temperature cycle is present, it can shift the air
masses above the ocean, often making wet places dry (drought prone) and dry
places wet.
Finally, deforestation for agriculture and/or building combined with the resultant
erosion can also cause drought to begin because as soil is moved away from an
area it is less able to absorb moisture when it falls.
It can be caused by not receiving rain or snow over a period of time. Wind patterns
that move clouds and moisture through the atmosphere can cause a place to not
receive its normal amount of rain or snow over a long period of time.
If you live in a place where most of the water you use comes from a river, a
drought in your area can be caused by places upstream from you not receiving
enough moisture. There would be less water in the river for you and other people
who live along the river to use.
Droughts are a common feature of climate in California, Colorado, Georgia, and New York, as
well as in Brazil, Southeast Asia, Southern Africa, and Australia.
Damage
Depending on the location, crop failures, famine, high food prices, and deaths can
occur. One of the scariest parts of a drought is the onset time. Unlike other forms of
severe weather or natural disasters, droughts often develop slowly.
1. There are three main ways droughts impact lives and communities. First, the
economic impacts of drought include losses in the timber, agricultural, and
fisheries communities. Many of these losses are then passed on to consumers
in the form of higher commodity pricing.
2. Next social impacts include increased chance of conflict over commodities,
fertile land, and water resources. Other social impacts include abandonment
of cultural traditions, loss of homelands, changes in lifestyle, and increased
chance of health risks due to poverty and hygiene issues.
3. Finally, the environmental impacts of drought include loss in species
biodiversity, migration changes, reduced air quality, and increased soil
erosion.
Periods of droughts can have significant environmental, agricultural, health,
economic and social consequences. 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
as a major food source are more vulnerable to famine.
In the United States, droughts can have major impact on agriculture, recreation and tourism, water supply,
energy production, and transportation.. Nationwide losses from the U.S. drought of 1988 exceeded $40
billion, exceeding the losses caused by Hurricane Andrew ,the Mississippi River floods of 1993, and the
San Francisco earthquake in 1989.
The effects of drought — a lack of precipitation or water reserve for irrigation — make it difficult to
support food crops. A prolonged drought could lead to famine. In the Horn of Africa, the 1984-1985
drought led to a famine which killed 750,000 people.
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:
Diminished crop growth or yield productions and carrying capacity for livestock
Dust bowls, themselves a sign of erosion, which further erode the landscape
Dust storms, when drought hits an area suffering from desertification and erosion
Famine due to lack of water for irrigation
Habitat damage, affecting both terrestrial and aquatic wildlife
Hunger, drought provides too little water to support food crops.
Malnutrition, dehydration and related diseases
Mass migration, resulting in internal displacement and international refugees
Reduced electricity production due to reduced water flow through hydroelectric
dams
Shortages of water for industrial users
Snake migration, which results in increase in snakebite reported
Social unrest, riots
War over natural resources, including water and food
Wildfires, such as Australian bushfires, are more common during times of drought
Description/types
Types of Droughts
1. Hydrological Drought
Many watersheds experience depleted amounts of available water. Lack of
water in river systems and reservoirs can impact hydroelectric power
companies, farmers, wildlife, and communities.
2. Meteorological Drought
A lack of precipitation is the most common definition of drought and is usually
the type of drought referred to in news reports and the media. Most locations
around the world have their own meteorological definition of drought based
on the climate normals in the area. A normally rainy area that gets less rain
than usual can be considered in a drought.
3. Agricultural Drought
When soil moisture becomes a problem, the agricultural industry is in trouble
with drought. Shortages in precipitation, changes in plant evaporation
(transpiration), and reduced ground water levels can create stress and
problems for crops.
When little or no rain falls, soils can dry out and plants can die. When rainfall is less
than normal for several weeks, months, or years, the flow of streams and rivers
declines, water levels in lakes and reservoirs fall, and the depth to water in wells
increases. If dry weather persists and water-supply problems develop, the dry
period can become a drought.