Drought: A prolonged period of months and years where supply of water falls below demand.
Distribution of Droughts
Because a drought is a prolonged period where the demand for water exceeds supply (water stress) then droughts can technically happen anywhere in the world. However, the most severe droughts tend to be located in certain areas of the world (shown in red on the map to the right) including:
Australia
Brazil
The Sahel (north Africa just below the the Sahara desert)
China and India
Parts of the US and Mexico and Southern Africa also suffer from droughts. The causes of droughts might not always be the same. North Africa and the Arabian peninsula are very arid, but because of the low population densities they don't suffer from regular droughts. Australia normally suffers droughts because of physical water scarcity (shortage of rain), whereas Brazil, India and China are more likely to suffer from economic water scarcity.
Some droughts may only last one season, but some like the ongoing drought in East African can last many years.
Desert: An arid area with very low levels of precipitation, making it impossible to support large amounts of vegetation, animals or people. Antarctica is technically a desert because of its low precipitation rates. The Sahara Desert is the largest traditional desert.
Water stress: When the demand for water exceeds the supply of water and shortages exist.
Physical Water Scarcity: When the supply of rainfall is lower than the demand of water.
Economic Water Scarcity: When water supplies exist, but the local population can not access them because of pollution, lack of technology, etc.
Hazards and Problems
Famine: Drought can lead to crop failures and livestock deaths that can lead to undernourishment and famine (food shortages).
Biodiversity Loss: Drought can cause plants and animals to die. Animals that drink large quantities of water like elephants can be some of the first to die.
Conflict: As water supplies begin to reduce then conflict over the remaining sources intensifies. This can be particular severe if resources are shared between countries or tribes.
Refugees: Because of the shortage of water and potential famine, people are forced to leave their home and often country to try and find food and water.
Desertification: A shortage of water can cause the land to start to degrade. Eventually this may lead to desertification (the land turning to desert).
Economic Loss: If a country is having to support refugees while at the same time seeing a decline in its exports (primary agricultural products) then the economy may decline.
Dependency: It is often poor countries that suffer from drought and it is these countries that find it hardest to cope, so often become dependent upon charities and international aid.
Education: As people suffer from undernourishment they often become weaker and are unable to teach and or go to school. Also during times of drought people (students and teachers) have to walk further to find water. All of these things would lead to a decline in the quality and quantity of education.
Measuring and Predicting Droughts
Droughts are measured on the Palmer drought severity index (PDSI). The index incorporates both drought and wet conditions. The index was first developed in 1965 and it looks at supply and demand of water. The index has been found best to measure long-term droughts lasting several months or longer.
Because droughts are prolonged periods without rain it is possible to calculate and see where droughts are most likely to happen. Countries and NGOs will often make appeals before the peak of droughts to ensure that areas are prepared for drought and possible famine. It is believed that global warming will increase the frequency and magnitude of drought events.
East Africa Drought (2011)
East Africa (or the area sometimes referred to the Horn of Africa) started suffering from a severe drought from mid-July in 2011. It is believed to be the worst drought in over 60 years and covers areas in Somalia, Kenya, Ethiopia, Eritrea, Djibouti and Sudan (now South Sudan). The drought was primarily caused by failing rains. The area received 30% less rain than the average between the years 1995-2010. In some areas the rains failed completely. The drought has been blamed on the deaths of between 50,000 and 100,000 people.
The drought has caused numerous problems including:
Crop failures and livestock deaths leading to rising food prices and food shortages (famine)
Over 920,000 refugees being forced to leave Somalia
An increase in measles outbreaks in refugee camps
An increased risk of malaria due to people living outside and in tents
An increase in sexual violence committed against refugees along with an associated risk of contracting HIV
From the outbreak of the drought the UN estimated that about 12 million individuals need food aid and requested $2.5 billion in humanitarian assistance. A large shortfall and a slow response are blamed on thousands of deaths. The reluctance of Al Shabab (an Islamist group) to allow aid groups to work in Southern Somalia is also blamed on a large number of deaths.
Remember drought (water stress) is when demand exceeds supply. Therefore drought can be caused by a combination of human and physical factors. Some of the most common causes are shown in the table below.
Deforestation: Cutting down trees which not only means the land will be receiving less nutrients and be less stable, but it can also mean reduced transpiration rates and reduced rainfall.
Overpopulation: As the world population continues to grow (now about 7 billion) the demand for water, for domestic use increases.
Industrial and Agricultural Demand: As the world's population grows bigger, more food is needed and more commodities demanded. Both of these increase the demand for water.
Economic Development: As countries develop and individuals get richer, they tend to use more water e.g. showers, toilets, gardens, cars, etc.
Rising Temperatures: As global temperatures increase more water is needed to grow crops and more water is lost through evaporation.
Falling Rainfall: The reduction in rainfall significantly reduces the supply of available water.
Droughts
Drought: A prolonged period of months and years where supply of water falls below demand.
Distribution of Droughts
Because a drought is a prolonged period where the demand for water exceeds supply (water stress) then droughts can technically happen anywhere in the world. However, the most severe droughts tend to be located in certain areas of the world (shown in red on the map to the right) including:
Parts of the US and Mexico and Southern Africa also suffer from droughts. The causes of droughts might not always be the same. North Africa and the Arabian peninsula are very arid, but because of the low population densities they don't suffer from regular droughts. Australia normally suffers droughts because of physical water scarcity (shortage of rain), whereas Brazil, India and China are more likely to suffer from economic water scarcity.
Some droughts may only last one season, but some like the ongoing drought in East African can last many years.
Horn of Africa - A Vision of Hell - BBC article
Key Terminology and Hazards
Arid: Arid means extremely dry, lack of moisture.
Desert: An arid area with very low levels of precipitation, making it impossible to support large amounts of vegetation, animals or people. Antarctica is technically a desert because of its low precipitation rates. The Sahara Desert is the largest traditional desert.
Water stress: When the demand for water exceeds the supply of water and shortages exist.
Physical Water Scarcity: When the supply of rainfall is lower than the demand of water.
Economic Water Scarcity: When water supplies exist, but the local population can not access them because of pollution, lack of technology, etc.
Hazards and Problems
Famine: Drought can lead to crop failures and livestock deaths that can lead to undernourishment and famine (food shortages).
Biodiversity Loss: Drought can cause plants and animals to die. Animals that drink large quantities of water like elephants can be some of the first to die.
Conflict: As water supplies begin to reduce then conflict over the remaining sources intensifies. This can be particular severe if resources are shared between countries or tribes.
Refugees: Because of the shortage of water and potential famine, people are forced to leave their home and often country to try and find food and water.
Desertification: A shortage of water can cause the land to start to degrade. Eventually this may lead to desertification (the land turning to desert).
Economic Loss: If a country is having to support refugees while at the same time seeing a decline in its exports (primary agricultural products) then the economy may decline.
Dependency: It is often poor countries that suffer from drought and it is these countries that find it hardest to cope, so often become dependent upon charities and international aid.
Education: As people suffer from undernourishment they often become weaker and are unable to teach and or go to school. Also during times of drought people (students and teachers) have to walk further to find water. All of these things would lead to a decline in the quality and quantity of education.
Measuring and Predicting Droughts
Droughts are measured on the Palmer drought severity index (PDSI). The index incorporates both drought and wet conditions. The index was first developed in 1965 and it looks at supply and demand of water. The index has been found best to measure long-term droughts lasting several months or longer.
Because droughts are prolonged periods without rain it is possible to calculate and see where droughts are most likely to happen. Countries and NGOs will often make appeals before the peak of droughts to ensure that areas are prepared for drought and possible famine. It is believed that global warming will increase the frequency and magnitude of drought events.
East Africa Drought (2011)
East Africa (or the area sometimes referred to the Horn of Africa) started suffering from a severe drought from mid-July in 2011. It is believed to be the worst drought in over 60 years and covers areas in Somalia, Kenya, Ethiopia, Eritrea, Djibouti and Sudan (now South Sudan). The drought was primarily caused by failing rains. The area received 30% less rain than the average between the years 1995-2010. In some areas the rains failed completely. The drought has been blamed on the deaths of between 50,000 and 100,000 people.
The drought has caused numerous problems including:
From the outbreak of the drought the UN estimated that about 12 million individuals need food aid and requested $2.5 billion in humanitarian assistance. A large shortfall and a slow response are blamed on thousands of deaths. The reluctance of Al Shabab (an Islamist group) to allow aid groups to work in Southern Somalia is also blamed on a large number of deaths.
Remember drought (water stress) is when demand exceeds supply. Therefore drought can be caused by a combination of human and physical factors. Some of the most common causes are shown in the table below.
East Africa drought: DEC appeals for funds - BBC article
Slow response to East Africa famine 'cost 'lives' - BBC article
East Africa drought: Cholera outbreak in Kenya camp
Somalia's al-Shabab militants close UN aid offices - BBC article
HUMAN CAUSES
PHYSICAL CAUSES
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