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Tan Cai Yi 33/09
Geography – Tutorial 8: Droughts
Explain the causes of droughts. With reference to an example or examples, discuss the
problems of managing an inhabited environment prone to droughts.
[16 marks]
Droughts occurs when a region experience a deficiency in its water supply for an
extended period of months or even years. Droughts happens as there is insufficient
moisture in the air and soil, which in turns hinder the process of rain formation and
hence, resulting to the shortage of water.
The causes of droughts can be classified into 2 forms, mainly natural and anthropogenic.
Firstly, the shifts of the Intertropical Convergence Zone (ITCZ) may result in droughts.
Regions which lies in the fluctuating zone of the ITCZ will experience a pronounce wet
and dry season, where rainfall will concentrate in a certain period of the year, mainly
five to six months. The shift in ITCZ is due to movement of the overhead sun, which will
then lead to a shift in the rain belts. During the period where the sub-tropical high
pressure belt lies in a region, the region will experience a dry season. The high pressure
belt is also known as the descending limb of the Hadley cell. This will hinder cloud
formation and hence, limit the amount of rainfall. Due to the limited amount of rainfall,
droughts may occur when precipitation is constantly below average.
Next, El Nino is the second natural cause of droughts. El Nino is characterized by the
extensive warming of surface waters in the tropical eastern Pacific Ocean. This is
coupled by the Southern Oscillation, where there are changes in the surface pressure in
the tropical western Pacific. This occurs across the tropical Pacific Ocean on an average
every five years. The walker circulation explains the movement of air, resulted from
pressure difference. The equatorial regions will experience a reversal in pressure,
precipitation, winds and ocean currents during an El Nino event. This will then shift the
ITCZ southwards and cause the trade winds to weaken in strength. This lack of air
movement for cloud formation will in turn lead to drier conditions and hence, droughts
occur.
In addition, global warming may intensify the difference of the wet and dry seasons as it
may cause shifts in positions of the climatic boundaries. This may cause the wet seasons
to be wetter (experience more rainfall) and the dry seasons to be drier (even lesser
rainfall). This is because green-house gases such as carbon dioxide absorb energy and
cause an increase in temperatures. An increase in temperatures will cause cloud
formation to be more difficult as the capacity to hold moisture of the air increases and it
will be harder to reach the dew-point for clouds to form. Moreover, if the region lies in
the descending limb of the Hadley cell, there will be even lesser clouds formed as the
sinking air hinders cloud formation. This will thus lead to a drier condition and droughts
will occur.
Lastly, human activities will also cause droughts. An increasing population will lead to an
increase in the demand for food. Man will then exploit the existing lands to obtain
higher crop yields and convert other natural ecosystems into farmlands to meet the
growing demand for food. This will give rise to desertification due to over cropcultivation. Also, the improvement in technology has also taken a toll in the
environment as man now release more green-house gases into the atmosphere,
exacerbating the effect of global warming, where more long radiation will be trapped in
the earth. This, coupled with desertification, will lead to droughts in the long run.
One example of regions which are more prone to droughts will be the Sahel, which lies
between the Sahara desert (North) and the Sudanian savannas (South), between
latitudes 13 degrees North to 17 degrees North. The mean annual temperature of the
Sahel is between 28 degree Celsius and 30 degree Celsius. This is a semi-arid area, with
rainfall approximately 200mm annually. The rainfall of this region is not constant and is
mostly concentrated between June to September. Due to the environmental conditions,
droughts do occur in this region frequently. Severe droughts may also occur when the
wet season is delayed or there is a decrease in the amount of rainfall. One of the most
severe droughts that had occurred in the Sahel happened between the 1960s to the
1980s. This drought had led to a widespread famine in Sahel and killed approximately
100, 000 people, left 750, 000 people dependent on food aid and affected almost the
whole population of 50 million living in the region.
One of the most prominent causes of the drought is due to over-exploitation of the land
in Sahel. As Sahel is a region comprised of many different countries, the difference in
cultural backgrounds will lead to various land uses. In the North, patorialism is more
dominant while arable farming is more dominant in the South. Technology had also
encouraged even greater exploitation of the land, causing existing dry lands to become
even drier and hence, increasing desertification in the Sahel. Due to the geographical
location of Sahel, continental droughts are already occurring in the region. These human
activities had exerted greater pressure on the land and the degradation of the land will
worsen the existing drought conditions. However, it is important to note that the
difference in the forms of agriculture exerts different levels of pressure on the land as
not all lands experience the same level of exploitation and overcrowding.
Management of droughts is difficult as droughts are hard to recognize, especially during
the initial stages. Hence, the severity of the drought is unable to be determined until the
hazard had occurred. In the case of Sahel, the incompetent government had failed to
recognize the severity of the situation. This led to the lack of government support and
arable lands have been misused, worsening the drought conditions. Also, political
instability and economic difficulties have contributed significantly to the management of
the situation.
Hence, we can conclude that the problems in managing the droughts is difficulty in
recognizing the drought and poor governance will exacerbate the situation when
policies and aid are not prompt.