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Lecture 21 Env. hazards (cntd).ppt

Lecture 21 Env. hazards (cntd).ppt - LECTURE 21...

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LECTURE 21: ENVIRONMENTAL HAZARDS (PART 2) Course Instructor: Md Asif Rahman (ASR) Lecturer, Department of Mathematics and Natural Sciences (MNS) University Building 2 (15 th Floor) E-mail: [email protected]
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DROUGHT A drought is an extended period of time like months or years when a region experience a deficiency/scarcity in its water supply. Generally, this occurs……. when a region receives consistently below average precipitation. It occurs when wind and pressure pattern are different from normal, so that expected rains do not fall.
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TYPES OF DROUGHT Meteorological আবহগত Drought - Related to rainfall amounts. - is generally defined by comparing the rainfall with the average rainfall for that place/region. -Atmospheric conditions that result in deficiencies ঘঘাটতত of precipitation change from area to area. - leads to depletion গঘাসতঘা of soil moisture - & this almost always has an impact on crop production.
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Agricultural Drought Related to availability of water to crops. When there is not enough water available for a particular crop to grow at a particular time. This drought is not only dependant on the amount of rainfall but also on the correct use of water. Agricultural drought mainly effects food production and farming. Agricultural drought links various characteristics of meteorological drought to agricultural impacts, focusing on precipitation shortages, soil water deficits, reduced ground water or reservoir levels, and so on. Deficient topsoil moisture at planting may stop germination অঙ ঙর / অঙ ঙররঘাদম , leading to low plant populations.
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Hydrological Drought - Hydrological drought is associated with the effects of periods of precipitation shortages on water supply. - Affects uses which depend on water levels. - Water in hydrologic storage systems such as reservoirs and rivers are often used for multiple purposes such as flood control, irrigation, recreation, navigation নননৌচঘালনঘা , hydropower, and wildlife habitat. Competition for water in
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