Droughts

1. Droughts School: Abdallah Al-Alayly Teacher: Ms. Abeer Abdallah Prepared by: Grade 9 students

2. Definition of Droughts • Drought is a normal, recurrent feature of climate, although many erroneously consider it a rare and random event. It occurs in virtually all climatic zones, but its characteristics vary significantly from one region to another. Drought is a temporary aberration; it differs from aridity, which is restricted to low rainful regions and is a permanent feature of climate.

3. The Nature of Droughts • Drought is essentially an imbalance of the hydrologic cycle. In this cycle, water vapor enters the atmosphere by evaporation from oceans, lakes, and ground surfaces and by transpiration from plants. Water is returned to the earth in the form of rain or snow. Some of it recharges the soil moisture, some accumulate in bodies of water, and some runs off to the oceans. Thus drought can result simply from a deficiency in precipitation over a period of time, or it maybe caused or by excessive evaporation and transpiration.

4. Causes of Drought • lack of a precipitation • high temperature, strong wind, and low humidity all of which increase the loss of moisture • shifting of normal cyclone (low pressure storm system) tracks across a region • High pressure systems in which cold, dense air sinks and is warmed by compression • abnormally low sea surface temperature • Human activities also contribute to the development of drought conditions; poor cropping methods and improper soil conservation techniques often contribute to create the drought.

5. Effects of Droughts Primary effects: • Primary effects of drought result from a lack of water. As a dry period progresses and water supplies dwindle, existing water supplies are overtaxed and finally dry up. The primary losses are loss of crops low of livestock and other animals, and loss of water for hygienic and drinking. Secondary effects of drought: • As water supplies swindle and crops and fodder are depleted, families begin to migrate in search of better grazing lands for their herbs or move to cities to seek jobs and alternative sources of income. • The migration may, in itself, contribute to spreading the scope of the disaster, especially if grazing animals are moved with people. • If drought is long term, it may result in permanent changes of settlement, social, and living patterns • major ecological changes, such as increased scrub growth, increased flash flooding and increased wind wing erosion of soils.

6. Examples Bolivia: • The drought during 1983 had affected large areas of 7 of the Bolivia’s nine departments, 80% of crops were lost. 35% of Bolivia’s total land area was directly affected. The drought deprived 1.6 million peasant farmers to their source of income and food supply.Total agricultural losses were estimated at U.S. $417.2 million. Cambodia: • Cambodian farmers plant rice seedlings into a bone dry paddy field in Kampong Speu province, 25 miles west of Phnom Penh. Rice production is being hit by the worst drought in 20 years.