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Case Study - Sahel:

Sahel is a semi-arid region across the north of Africa. Some of the countries that it covers are Chad, Mali, Niger. Nigeria and Burkina Faso. It is meant to have 2 seasons (one being wet and the other dry) but it has a very unreliable water supply and thus ends up only having 1 or 2 months of rainfall where the total amount of rainfall is between 250 and 450mm. They have a low rainfall for 2 resons.

Firstly it is because there are many mountains near the region. Relief rainfall takes place and this is when the clouds are dense with water. As they rise to pass the mountains, the air temperature decreases causing the water to cool and be released from the cloud. Therefore when the wind passes over the mountains, there is no rain left in the cloud for it to rain. Therefore, the area on one side of the mountain gets very little rainfall.

Secondly this is because it is a landlocked area near the equator. The heat at the equator causes evaporation of the sea water to increase. However because most parts of the Sahel aren't at the coast, the countries get very little rainfall when compared to others.  

Sometimes the rain comes in terrential down pours and then the rest of year is spent in drought. This increases soil erosion and desertification. Therefore 60% of the population are subsistence farmers as their crop yield or farming techiniques arent reliable; they need enough food to at least provide for themselves and their family. 

Hydrological cycle:

The hydrological cycle is a closed system. The water is reused again and again, no extra water is added or lost in the cycle.

Effects of climate change on the Hydrological Cycle:

Firstly, climate change is likely to increase precipitation intensity. This would mean that a larger proportion of rain would fall in a shorter period of time. This will increase flood risks and surface run-off. Especially for Bangladesh, flood rates could almost wipe out the whole country!

Secondly, climate change is increasing global warming. As the atmosphere gets warmer, the evaporation rate increases. This leads to an increased amount of moisture in the atmosphere, which means that soil surfaces will be dryer thus making drought more likely. Countries in Est Africa (e.g. Burkina Faso) will suffer even more drought than they already have; thus leading to further problems including hunger, malnutrition, disease, increased death rate. Additionally, the wetlands can evaporate so the very little water sources remaining in the Sahel will be available for use.

Lastly, climate change is likely to affect the ocean flow. This is because the warmer temperatures are adding fresh water from the melting ice caps into the oceans. This is changing their currents and increasing surface run-off thus leading to more floods. The shrinking glaciers in the Himalayas will affect the water source for the river Ganges and could increase flood risk.  

Overall, climate change will have a massive change on the hydrological cycle causing


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