Detailed notes that summarise the Geography IEB syllabus of Droughts. Included in these notes are important definitions and concepts to learn as well as diagrams that make the section more understandable.
• The areas most at risk for droughts are the areas alongside deserts. These
are semi-arid regions with low rainfall.
• The most drought prone region in Africa is known as the Sahel. These
grasslands extend from Senegal in the west to northern Ethiopia in the
east.
• The horn of Africa- Ethiopia and Somalia- is also drought prone.
• In Southern Africa, the areas alongside the Kalahari desert are most at risk
for drought. The rainfall decreases as you move from east to west across
South Africa, this means that the risk of drought increases in the same
direction.
Causes
Physical
Temperature of oceans and land
Precipitation is driven by the heat of the sun; the hotter it is, the greater the
rate of evaporation. Thus, if the temperature of the ocean or the land is
relatively cool in a certain area, drought can occur as there will be less
evaporation.
Air Circulation patterns in the atmosphere
Large scale weather patterns are mainly due to the pattern of air circulation
which are caused by temperature. When there is an anomaly in surface
temperatures, typical patterns of air circulation and rainfall change. This
leads to higher rainfall in some areas and drought in others. El nino and la
nina are prime examples of this.
Human
Deforestation
Widespread deforestation can contribute to drought. Forests lose water
through evapotranspiration which feeds the local water cycle. When forests
are cut, there is less water evaporating which reduces the amount of cloud
formed.
Soil Degradation
Soil degradation occurs when protective plant cover i lost exposing the soil.
This reduces ability of the soil to absorb and hold water, so soils dry up
quickly and cannot support growth of plants and crops.
Increased Demand for water
Climate change and drought
Increases in temperature have the potential to cause more frequent and
severe droughts.
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