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I.3 Droughts


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I.3 Droughts

  1. 1. HAZARD #3: DROUGHTS20 million people lacked food during the 2003 drought in EthiopiaDrought: extended period of dry weather leading to extremely dry conditions• “Meteorological drought” = due to prolonged period with less average rainfall• “Agricultural drought” = drought due to poor agricultural planning (soil erosion, water usage exceeding carrying capacity) when not enough water is available for the type of agriculture used in a particular region• “Hydrological drought” = due to water reserves (aquifers, lakes, etc) slowly falling below average (ex: Aral Sea in Kazakhstan)
  2. 2. CHARACTERISTICS OF DROUGHTS; THREE TYPES OF DROUGHTSCASE-STUDIES IN TEXTBOOK p.208:• Europe (2003)• Horn of Africa (2003)Compare and contrast the causes and consequences of these two droughts in 2003
  4. 4. CHARACTERISTICS OF DROUGHTS: CAUSES• HIGH PRESSURE SYSTEMS:Increased aridity can be caused by high pressure systems (= prevents upwardcondensation over oceans and cloud formation), particularly if over continentalmasses (less moisture available) (ex: less than average rainfall in the Horn of Africain 2011 due to persistent high-pressure anticyclone over the region)• OCEANIC / ATMOSPHERIC WEATHER CYCLES:ENSO (El Niño Southern Oscillation) creates cyclic droughts in Australia andAmericas: cyclic warming (El Niño) of the Eastern Pacific Ocean disrupting usualwind/current patterns and resulting in droughts in Australia/rainfall in Mexico/Peru.El Niño is usually followed by La Niña, cooling of the Pacific resulting in oppositeconsequences (dry eastern coastlines, wet western coastlines)• HUMAN ACTIVITY:Poor farming techniques, excessive irrigation, deforestation, erosion, riverdiversions, etc
  5. 5. DROUGHTS: SPATIAL DISTRIBUTION OF PERMANENTLY ARID REGIONSExplain the permanent aridity in the following regions:• Kalahari and Australia• Takla Makan and Great Basin• Atacama and Namib
  6. 6. NATURAL AND HUMAN CAUSES OF DROUGHTS 1. Describe the consequences of the ENSO (El Niño Southern Oscillation) on each side of the Pacific ocean 2. Referring to named examples, suggest other human factors which may contribute to creating/increasing droughts