Learning objectives: Specific climatic conditions leads to drought Natural hazards occur when events adversely affect people Droughts are responsible for hazards such as crop failure, famine, wildfires
In the UK an official drought is declared when at least 15 consecutive days go by without more than 0.2mm of rain. In the Sahel, a drought is declared when there’s below average rainfall for 2 years. The Sahel has actually suffered drought for most of the last 30 years.
Drought is often quoted as one of the major natural hazards of the developing world Drought killed just under 10 million in China in Drought is different from other hazards unlike floods and tropical storms it never kills people directly
Drought is declared in the UK when 15 consecutive days go by with no more than how much rainfall? When is drought declared in the Sahel? How is drought different to other climatic hazards?
On a global scale drought prone areas can be predicted with accuracy Tropical high pressure zones will have low rainfall as air descends e.g. Sahara desert Whilst these areas are drought prone their lack of rainfall is not seen as natural hazard as the populations there are very small and dispersed
Drought is mostly a hazard in the semi-arid regions adjacent to the desert areas. Here seasonal rainfall allows agriculture and has sustained a large population. Millions of people are therefore affected by any change in the pattern of rainfall
This is the semi arid region south of the Sahara consisting of 6 countries: Senegal Mauritania Mali Burkina Faso Niger Chad
Why are droughts in desert areas such as the Sahara not a natural hazard? In which areas is drought the biggest hazard? Name the 6 countries in the Sahel region of Africa.
Sometimes the wet season does not arrive or lasts a shorter than usual time The ITCZ does not migrate as far North as it usually does. This is due to the influence of sea temperatures.
What does ITCZ stand for? Why is it important to the Sahel? What causes the failure of the wet season?
Watch the video and then explain how this phenomenon causes drought.
Drought is often worsened by ecosystem degradation Over cultivation – takes too much nutrients from the soil results in erosion leading to desertification Overgrazing – animals eat plants soil no longer protected Decline of traditional nomadic lifestyle due to conflicts and changes in farming due to pressure of increased population. Removal of bushes and small trees for fuel meeting the demand of an increased population
overgrazing Over cultivation Over population Decline of traditional nomadic herders desertification causes
Long periods of high atmospheric pressure (anticyclones) clouds don’t form so it doesn’t rain. Long periods of high temperatures. This means more evapotranspiration than precipitation. Land use e.g. agriculture uses a lot of water High population density strain on resource Changes in the way we live, and increasing wealth e.g. power showers, dishwashers.
Disrupts lifestyles – Watch the video clip 2003 European heat wave sparked wildfires in Portugal which killed people. Harvests fell dramatically. Water tables fall small rivers dry up can affect aquatic life
What are the 5 causes of drought in the UK?
Improved forecasting – monitoring El Nino and other surface temperature anomalies may give an advance warning of droughts caused by complex atmospheric circulations. Ecosystem monitoring – spots early signs of land degradation Improved water conservation – low tech e.g. stone piles or bunds, agroforestry. High-tech drip irrigation, increase fertilizers, genetically engineered crop varieties.
Water rates increase Free installation of water saving devices Non essential uses banned e.g. hose pipe Reclaim water from sewage treatment plants. Repair water pipes Build reservoirs in wetter places and pipe to more populated areas
Do you feel that you could answer the exam question given? Do you think that “test bite powerpoint talk” is a good way to learn? Homework answer the exam question