Keiths drought ppt
- 1. By group 3
- 2. WHAT IS A DROUGHT? • A drought is a period of below-average precipitation in a given region, resulting in prolonged shortages in its water supply, whether atmospheric, surface water or ground water. A drought can last for months or years, or may be declared after as few as 15 days. It can have a substantial impact on the ecosystem and agriculture of the affected region and harm to the local economy. • Many plant species, such as those in the family Cactaceae (or cacti), have adaptations like reduced leaf area and waxy cuticles to enhance their ability to tolerate drought. Some others survive dry periods as buried seeds. Semi- permanent drought produces arid biomes such as deserts and grasslands.
- 3. WHAT CAUSES DROUGHTS? THERE ARE MANY REASONS FOR DROUGHTS TO OCCUR : • PRECIPITATION DEFICIENCY • DRY SEASON • EROSION AND HUMAN ACTIVITIES • CLIMATE CHANGE
- 4. Precipitation deficiency • Mechanisms of producing precipitation include convective, stratiform , and orographic rainfall. Precipitation can be divided into three categories, based on whether it falls as liquid water, liquid water that freezes on contact with the surface, or ice. • drought can be triggered by a high level of reflected sunlight and above average prevalence of high pressure systems, winds carrying continental, rather than oceanic air masses, and ridges of high pressure areas aloft can prevent or restrict the developing of thunderstorm activity or rainfall over one certain region. • Once a region is within drought, feedback mechanisms such as local arid air, hot conditions which can promote warm core ridging, and minimal evapotranspiration can worsen drought conditions.
- 5. Dry season • Within the tropics, distinct, wet and dry seasons emerge due to the movement of the Intertropical Convergence Zone or Monsoon trough. The dry season greatly increases drought occurrence, and is characterized by its low humidity, with watering holes and rivers drying up. • Since water vapor becomes more energetic with increasing temperature, more water vapor is required to increase relative humidity values to 100% at higher temperatures (or to get the temperature to fall to the dew point). Periods of warmth quicken the pace of fruit and vegetable production, increase evaporation and transpiration from plants,and worsen drought conditions.
- 6. Erosion and human activities • Human activity can directly trigger exacerbating factors such as over farming, excessive irrigation, deforestation, and erosion adversely impact the ability of the land to capture and hold water. In arid climates, the main source of erosion is wind.Erosion can be the result of material movement by the wind. The wind can cause small particles to be lifted and therefore moved to another region (deflation). Suspended particles within the wind may impact on solid objects causing erosion by abrasion. Wind erosion generally occurs in areas with little or no vegetation, often in areas where there is insufficient rainfall to support vegetation.
- 7. Climate changes • Activities resulting in global climate change are expected to trigger droughts with a substantial impact on agriculture throughout the world, and especially in developing nations. Overall, global warming will result in increased world rainfall. Along with drought in some areas, flooding and erosion will increase in others.
- 8. Major drought prone areas of the world 1. Ethiopia Almost certainly the poorest country in the world, Ethiopia has the most vulnerability towards drought. It’s been ranked at 172nd position out of 174 regarding overall development which proves its absolute poverty. 2. Eritrea Located on the horns of the African continent and mostly caught in the hands of war, Eritrea is another country with an alarming rate of poverty all around. 3. Somalia Located in the horns of African continent alongside Eritrea, the federal republic of Somalia has faced one of most catastrophic droughts in the history.
- 9. Common consequences of drought include: • Diminished crop growth or yield productions and carrying capacity for livestock. • Dust bowls, themselves a sign of erosion, which further erode the landscape. • Dust storms, when drought hits an area suffering from desertification and erosion. • Famine due to lack of water for irrigation. • War over natural resources, including water and food • Hunger, drought provides too little water to support food crops. • Snake migration, which results in snakebites.
- 10. • The components of a drought preparedness and mitigation plan are the following: 1.Prediction 2.Monitoring 3.Impact assessment 4.Response.
- 11. bibliography • Causes of drought-Wikipedia.com • Major drought prone areas-toplistenz.com • Consequences of droughts-wikipidia.com • Mitigation-threeissues.sdsu.edu