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What is a Drought?
A drought is a period of time in which a specific area experiences a water deficit. Droughts are a normal element of climate, which will affect all climate zones once is a while. Hydrological and meteorological are the two different perspectives in which drought is most often discussed.
Meteorological droughts focus on the deficiencies in measured precipitation. They then compare each year's measurements to what is said to be normal in terms in the amount of precipitation. Drought is then determined from that aspect. The hydrological perspective monitors droughts by looking at stream flow and reservoir, lake, and aquifer water levels. This perspective also considers precipitation as it contributes to the water levels.
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There is also a type of drought known as an agricultural drought that can cause changes to a variety of species' natural distribution, as well as impact crop production. Farms can also cause droughts when soil cannot absorb a lot of water due to being depleted. Agricultural droughts can also be caused by natural droughts.
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Droughts can be caused by a number of things. The most important drought cause is related to how much water vapor is in the atmosphere because water vapor in the atmosphere is what causes precipitation. When there are moist, low pressure systems, precipitation, such as rain, hail, sleet, and snow can occur. If the presence of dry, high pressure is above average, there will be less moisture available to create precipitation. This then results in a water deficit in areas they move over.
This can also occur when air masses are shifted by winds, resulting in dry, warm, continental air moving over an area instead of moist, cooler, oceanic air masses. El Nino, which affects the temperature of the ocean's water, also impacts levels of precipitation because during the years in which the temperature cycle is present, the air masses can be shifted above the ocean, often leading to places that are typically wet, dry and making places that are typically dry, wet.
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The first stage of drought is a watch or warning and this stage is considered the least severe. The next stages are most often referred to as a drought disaster, emergency, or critical drought stage. After a drought has been going on for a prolonged period of time, the final stage begins. During the final stage public water use is limited. During this stage, areas will often put disaster plans into place as well.
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There are always short-term and long-term consequences of a drought, regardless of its stage. The associated problems can have environmental, economic, and social impacts on the areas in which the droughts occurs, as well as the areas that have relations to the areas in which the drought occurred. The economic impacts tend to primarily impact the agricultural industry. The environmental impacts can include increased erosion, plant diseases, landscape and habitat degradation, insect infestations, and a decrease in air quality. There is also the risk of wildfires. The social impacts can include inequalities in water distribution amongst the poor and the wealthy, disputes between those who need to use the available water, a decline in health, and disparities in areas that need disaster relief.
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ThinkQuest. (2011). Drought. Retrieved on April 20, 2011 from ThinkQuest: http://library.thinkquest.org/16132/html/drought.html
NASA Earth Observatory. (2011). Drought: The Creeping Disaster. Retrieved on April 20, 2011 from NASA Earth Observatory: http://earthobservatory.nasa.gov/Features/DroughtFacts/
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Drought: Wikimedia Commons - Tomas Castelazo