2. The causes of drought Learning objectives:
To understand the different causes of drought and the physical and human impacts

3. What is the definition of drought?
Drought: A prolonged period of abnormally low rainfall, leading to a shortage of water. This means there is far less water in a particular area compared to what is normal for that same period of the year. Drought conditions are location-specific.
It is different to other hazards as it develops over a long period of time. Thus it is hard to define exactly when the drought began and ended.
In the UK a drought is declared when there are 15 consecutive days without more than 0.2mm of rainfall.
In the Sahel however, a drought is declared when there is below average rainfall for two years.

4. Taps Start to Run Dry in Brazil’s Largest City
February 2015
Taps Start to Run Dry in Brazil’s Largest City
Southeast Brazil grapples with its worst drought in nearly a century
June 2014
California Drought Causes Largest Water Loss in State History
The total statewide cost of the 2014 drought will be $2.2 billion
August 2014
Drought in China is worst in 63 years.
Taps running dry in Beijing

5. What are the causes of drought? Match the definition with the key term
Meteorological
This is how a decrease in precipitation can have an impact on overland flow, reservoirs, lakes and groundwater. This is often defined on a river basin scale; water reserves in aquifers, lakes and reservoirs fall below an established statistical average. This can be related to precipitation or human demand and increased usage
Hydrological
If a dam is constructed on a large river it can produce electricity and plenty of water for the area close to the dam. However, places further downstream may suffer from drought because they will be receiving a reduced flow of water. For example, the building of the Ataturk Dam on the River Euphrates provided electricity and water for irrigation in Turkey but has restricted the flow of water to Syria and Iraq, meaning they have less water for irrigation
Human- agricultural
This concerns the amount of precipitation an area receives compared to its average. It is all about the weather and occurs if there is a prolonged period of below- average precipitation, which creates a natural shortage of available water; this is then called a drought
Human- dam building
The cutting down of trees for fel reduces the soil’s ability to hold water. This can cause the land to dry out, which can result in drought in an area
Human- deforestation
This is where there is enough water available to support crop production on farms. This can occur when the crops are planted or during their growing season it often occurs when there is a fall in precipitation but can occur if farming techniques change. For example, farmers could use irrigation to start growing crops that require more water than is available; if the irrigation source dries up then the plants will die
Students either match them up or they walk around to find their match

6. Justify your choices of most and least devastating
Causes of drought
Definition
Meteorological
This concerns the amount of precipitation an area receives compared to its average. It is all about the weather and occurs if there is a prolonged period of below- average precipitation, which creates a natural shortage of available water; this is then called a drought
Hydrological
This is how a decrease in precipitation can have an impact on overland flow, reservoirs, lakes and groundwater. This is often defined on a river basin scale; water reserves in aquifers, lakes and reservoirs fall below an established statistical average. This can be related to precipitation or human demand and increased usage
Human- agricultural
This is where there is enough water available to support crop production on farms. This can occur when the crops are planted or during their growing season it often occurs when there is a fall in precipitation but can occur if farming techniques change. For example, farmers could use irrigation to start growing crops that require more water than is available; if the irrigation source dries up then the plants will die
Human- dam building
If a dam is constructed on a large river it can produce electricity and plenty of water for the area close to the dam. However, places further downstream may suffer from drought because they will be receiving a reduced flow of water. For example, the building of the Ataturk Dam on the River Euphrates provided electricity and water for irrigation in Turkey but has restricted the flow of water to Syria and Iraq, meaning they have less water for irrigation
Human- deforestation
The cutting down of trees for fel reduces the soil’s ability to hold water. This can cause the land to dry out, which can result in drought in an area
Rank the causes of drought from most to least devastating, where 1 is the most and 5 is the least.
Justify your choices of most and least devastating

7. Meteorological or hydrological?
Guatemala
Lake Mead
Amazon
Gujarat
Texas

10. ENSO (El Nino Southern Oscillation)
Annotate the diagram as we go along

11. Strong trade winds from east to west
El Nino
Describe the conditions during a normal year
A normal year:
Strong trade winds from east to west
Warm water
Cool water

12. El Nino year: Describe the conditions during an El Nino year
Weak trade winds move east
Warm water moves east

13. October 1997 showing the Pacific El Niño:

14. Why does the global circulation system make some locations more vulnerable to drought than others?
Use p84 and these resources to help you answer the question.

15. What’s caused the drought?
Write down three things you have learnt this lesson
Using the play doh, create a sequence to show what a cause of drought
Kangaroo: El Nino