Tuesday, October 29, 2013

Natural resources: Droughts

Drought is scarcity of water. Drought occurs due to:
  1. inadequate rainfall
  2. late arrival of rains and
  3. excessive withdrawal of groundwater
Scarcity of water for normal needs of agriculture, livestock, industry or human population may be termed as drought.
Drought is understood from dry weather which persists long enough to produce a serious hydrological imbalance, leading to damage of plants, animals and human life.

TYPES OF DROUGHT
Droughts are classified into four types:
  1. Meteorological Drought occurs when the total amount of rainfall is less than 75% of normal rainfall. This drought will be severe if the rainfall is less than 50% of the normal rainfall
  2. Hydrological Drought occurs when the total amount of rainfall is less than the average rainfall. It is generally associated with reduction of statistical average of water reserves available in the source such as aquifers, lakes and reservoirs.
  3. Agricultural Drought occurs due to the shortage as well as the timing of  overall rainfall. This form of drought reduces groundwater and reservoir levels. Agricultural Drought affects cropped plants.
  4. Socio-economic Drought occurs due to reduction in the availability of food and social security of people in the affected areas. Socio-economic drought leads to famine.
CAUSES OF DROUGHT
  1. When annual rainfall is below normal and less than evaporation, drought occurs
  2. High population also leads to drought. Population growth leads to poor land use and worsens the situation
  3. Intensive cropping pattern and over-exploitation of scarce water resources by digging wells or bore-wells for high productivity has turned drought prone areas into desert. Ex:- Over exploitation of water resources for sugarcane in Maharashtra has prevented the state from drought recovery for the past 30 years.
  4. Deforestation leads to desertification and drought. Deforestation leads to the top soil exposed to erosion by heavy rains, wind and the sun. Thus the top layer of soil rich in nutrients gets washed away making the soil unproductive. Eroded soils exhibit a droughty tendency.
EFFECTS OF DROUGHT:
  1.  Drought causes hunger, malnutrition and scarcity of drinking water. It also degrades the quality of drinking water
  2. Drought causes widespread crop failures leading to acute shortage of food thereby adversely affecting human and livestock populations
  3. Drought indicates the initiation of desertificarion
  4. Raw materials for agro-based industries are critically affected during drought thereby retarding industrial and commercial growth.
  5. Drought accelerates degradation of natural resources
  6. Drought leads to large scale migration to urban areas thereby creating slums.
DROUGHT MANAGEMENT :
  1. Indigenous knowledge in control of droughts and desertification is very useful for dealing with drought problems
  2. Rainwater harvesting program is very useful technique used to conserve water and control drought
  3. Construction of large capacity reservoirs is essential in drought prone areas
  4. Modern irrigation techniques (drip irrigation) is very useful to conserve water and avoid wastage
  5. Afforestation activities improve the potential of water in drought prone areas
  6. Mixed cropping and dry farming are suitable methods that minimize the risk of crop failure in dry and drought prone areas.

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