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HEATWAVES AND DROUGHTS

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DESCRIPTION

CAUSES OF DROUGHTS AND HEAT WAVES

WHERE OCCUR MOST OFTEN THE DROUGHTS

THE IMPACT OF DROUGHT

HISTORICAL DROUGHTS


  • IN SAHEL

Since the early 20th century a decrease in rainfall in the Sahel has caused a dramatic increase in the desert between 1968 and 1986, accompanied by a drought. More than 20 million hectares of formerly productive lands are transformed into barren desert each year (area greater than half of the British Isles). While all indications are that once the drought was limited to relatively small areas, their durations, their extensives and damages resulting constantly increased during the past 100 years.

 

  

During the drought of 1968 to 1973, often called "great drought" 16 countries were affected (the islands of Cape Verde, Senegal, Gambia, Mali, Mauritania, Burkina Faso, Chad, Niger, Benin, Nigeria, the Central African Republic, the Libya, the Sudan, Somalia, Djibouti and Ethiopia). From 1980 to 1984, 14 other nations of central and southern Africa experienced a drought.

The rainfall Chronicles :

-1910 to 1916 : period of drought ;
-1920 to 1970 : wet period mostly 1950 to 57 (7 years) ;
-1970-2003 : drought especially between 1971 to 1976 and 1980 to 1988, the longest and most intense of the century.
- but the drought slowly slowed since 1990.

 

The evolution of the anomaly of the rainfall in the Sahel from 1900
to now compared to the average from 1950 to 1979. Source JJASO.

Climatic phenomena AMO and TAV are those that have the most influence on rainfall over West Africa. Droughts in the Sahel have occurred primarily when the index of the AMO was negative either when the temperature anomaly in the North Atlantic was negative and opposite in the South Atlantic..

Click to see more info on the relationship between AMO and drought in the Sahel

The Sahelian zone underwent repeated climatic fluctuations as in all regions of our planet. In 2000 years the desert has almost doubled and the area of Lake Chad has decreased significantly.

 

The evolution of the environment according to the climate in the Sahel since 18.000 years

The "great drought" from 1968 to 1973, with a volume of rainfall of 15-40% lower than the average, has caused a loss of 600_000 tons on the harvest of cereals. In 1984 the rainfall is estimated as being fallen 25% and the total flow of Chari-Logone river was only about 20% of the long-term average. What has resulted in the fall in the level of Lake Chad. That demonstrates the effect of a reduction in the rainfall of 25% on the flow of a river. Thus the area of Lake Chad 23.500 km2 en 1963 in 1963 was more than 2.000 km2 in 1985.

 

In Mali Timbuktu was facing major challenges of significant climate change
occurred in the region. Above, two images of the city represented by the brown area
in the center of the upper part of the photograph. Left in 1976 and right in 1987, the
blue areas represent the floodplain of the River Niger while the sand dunes are yellow.

 

during the dry season in the West of the Sahel

 



during the wet season in the West in the Sahel

  • IN NAMIBIE

In other countries there is the same scenario that in the Sahel. This is the case in Namibia located south of Africa. For some parts of Southern Africa, crops are shrinking. Finally, it is expected that mosquitoes vectors of malaria spread until Namibia.

 

Click here to enlarge this photo which shows us that Namibia sand
dunes advance and may engulf the surrounding vegetation

 

Click here to enlarge photo of drained
Lake of Dead Vlei Sossusvlei Namibia


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