ZIMSEC O Level Geography Notes: Weather Hazards: Drought
- In general terms drought is caused by a general shortage of precipitation over an extended period of time usually the rain season resulting in water shortages for both human and natural activities.
- A more formal definition of defines drought as a protracted period of deficient precipitation resulting in extensive damage to crops, resulting in loss of yield.
- Droughts are often associated, but should not be confused with, famine which is an extreme shortage of food for part or most of the population.
- Droughts are a naturally occurring phenomena.
- Zimbabwe and Southern Africa often experiences cyclical droughts for example 1800-1830s,1844-49,1981-2, 1992 and in some parts during 2002. Generally a drought occurs at least once every decade although they may be becoming more frequent due to Global Warming.
- Areas in Matebeleland which generally receive less rain as they are further inland often suffer the severest droughts and more frequently even during times when the rest of the current receives normal rainfall.
- Countries in Northern Africa especially western African countries like Somalia and Ethiopia have more frequent droughts some of which last for years.
- Droughts have also been attributed to climate change.
- Although many theories have been put forth to explain the cause of droughts not much is known.
- The most dominant theory is the El Nino effect with some experts even linking droughts to volcanic eruptions.
- El Nino is a band of water whose temperatures hardly changes for long periods of time that is found on the Western coast of the South American continent.
- The warming up of these waters is known in the local Spanish language as El Nino (the Child in reference to baby Jesus as it tends to occur around Christmas).
- The cooling of these waters is known as the La Nina (Little Girl).
- Both phases are known as the El Nino Southern Oscilation Cycle (ENSO)
- During an ENSO the waters in the Pacific Ocean get warmer.
- Normal airflow moves westward from the Pacific to the Indian Ocean, but during El Nino this movement is weakened or altered.
- This results in high rainfall in some parts of Latin America but low rainfall and even drought in southern Africa.
- During the 1991-1992 drought El Nino lasted until the end of February 1992.
- During a La Nina Zimbabwe receives extremely large amounts of rainfall.
- Although droughts are a natural phenomena human actions may worsen their effects:
- Rapid population growth resulting in increased pressure on natural resources including water.
- Soil erosion.
- Falling water tables due to ground water being used for domestic and agricultural activities.
- Build up of salts also know as salination has destroyed a lot of land making it toxic to plants.
- Crops wilt and there may be a significant reduction in yields.
- Sometimes crops fail altogether.
- Animals die from dehydration and shortage of pastures.
- Shortage of drinking water
- Dust storms.
- Death of people due to dehydration and starvation.
- Malnutrition and associated conditions like Kwashiorkor these are more pronounced in children.
- Poverty due to loss of livelihood.
- Crops can become toxic due to an increase in aflatoxins especially to animals.
- Can lead to nitrate poisoning in animals which are fed drought affected crops such as maize.
- Wild fires become more frequent.
- Farmers can make use of insurance schemes.
- Stockpiling essential food crops in years of high yields using for example GMB silo storage.
- Practice irrigation using river and ground water.
- Cloud seeding
- Grow drought resistant crops and keeping drought resistant animals like donkeys.
- Grow early maturing crops.
- Appeal for aid from International organisations such as the UN, USAID, OxFam, Save the Child etc.
- Find alternative uses for drought damaged crops for example drought affected soya beans can be used to feed cattle.
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