Essay About Drought

Among the natural hazards through the last twentieth century, drought is known as the most detrimental phenomena. over land, drought characterized by below normal percipitaiton during a period of months to years and as a temporary dry period is contrast to the permanent aridity in arid an semi arid regions. Periods of low accumulated precipitations relative to normal conditions lead to drought events which are exacerbared by high temperature. Sustained periods of this phenomena can be disruptive to both natural systems and human. (Bruc, 1994, Obasi, 1994garne 20 Wehner et al., 2009, Dai, 2011, Burk et al., 2010). Drought is considered as the major factor limiting production in most parts of the world especially in arid and semi-arid areas

It is difficult to depict an absolute definition of drought. Drought has been classified into four categories including meteorological, soil moisture (agricultural), hydrological and socio-economic (Mishra and Singh 2010). Meteorological drought is defined by the lack of precipitation and often combined with higher than normal potential evapotranspiration for a long period of time. Hydrological drought can occur in both groundwater and streamflow, when lack of precipitation lead to shortage of surface and ground water. Long periods of drought with below average precipitation lead to groundwater droughts while streamflow droughts can result from shorter periods with no precipitation. Agricultural drought occurs when deficit of soil moisture negatively impact the crop yield. Socio-economic drought describes a status that there is a limit of water supply for economic goods (AMS, 2004). Guan (2015) to assess the impact of drought events of California in recent years, studied two factors including crop yield and crop area. Funding showed that the primary cause of reduction in crop yield is the drought-induced heat stress however the most of the overall reduction in crop production (more than 70%) is the result of decreasing in crop