If desertification is a continuous phenomenon that occurs in determined eco-climatic zones, drought on the contrary is an intermittent phenomenon that can occur in any zone. Drought is related to rainfall. It occurs when rainfall is below average in a year or during a number of years on end. In time of drought, the water needs of a biological (animal or plant) community cannot be met. Drought is a relative notion. It leads to aridity. Man has gone to the moon but he has little control over climatic phenomena such as drought, the occurrence of which cannot be reliably predicted.