Cycle of extremes: On droughts and flood

admin
By admin August 10, 2019 15:52

Long periods of drought and then a sudden bout of excessive rainfall, bringing floods, has become a hallmark of Indian Monsoon for last few years. A common feature of drought and floods with coexistence poses a potent threat that cannot be eradicated but has to be managed. The article suggests the crippling cycles of drought and floods to be addressed with redoubled vigour in India.

Drought in India:

  • As defined by the IMD, draught is a consequence of the natural reduction in the amount of precipitation for a long period of time.
  • Drought is often associated with other climatic factors like high winds and temperatures and low relative humidity. These factors can aggravate the severity of the drought event
  • As per the Manual for Drought Management 2016, drought is declared considering following two indicative factors:

a) The extent of rainfall deviation (depreciation)

b) The consequent dry spell

  • IMD declares a year to be a drought year, in case the area is affected by moderate and severe drought, either individually or together and for 20-40% of the total area of the country. A seasonal deficiency during South-West monsoon season in the country as a whole should be 10% or more.
  • A drought year is called ‘All India Severe Drought Year’ if its spatial coverage is more than 40% of the total area.
  • There are different types of droughts:

a) Meteorological Drought: When the seasonal rainfall over an area is less than 75% of its long term average value.

b) Hydrological Drought: It is a period during which the stream flows are inadequate to supply established use of water.

c) Agricultural Drought or Soil Moisture Drought: It occurs when soil moisture in an area becomes inadequate for healthy crop growth and cause extreme stress and wilting.

d) Socio-Economic Drought: It is a period of abnormal water shortage which affects all aspects of an economy in a region, thus causing social distress in terms of unemployment, migration, discontent and various other problems.

  • As reported by the Drought Early Warning System (DEWS), a real time drought monitoring platform, in March 2019, about 42% of India’s land area is under drought with 6% exceptionally dry – four times the special extent of drought last year
  • Andhra Pradesh, Bihar, Gujarat, Jharkhand, Karnataka, Maharashtra, parts of the North-East, Rajasthan, Tamil Nadu and Telangana (home to 40% of the country’s population, i.e 500 million people) are the worst hit. 

Causes of Drought:

  • Reduced rainfall
  • Air current disturbances obstructing presence of water vapour in different areas.
  • Unusual currents of warm and cold water in oceans.
  • Geographical structures reasoning for rain-shadow areas.
  • Increasing urbanisation and deforestation.
  • Faulty cropping system and imbalanced agro-climatology.
  • Unsustainable water usage for livelihood like industry, agriculture etc

Impacts of Drought:

  • Environmental loss
  • Increased stress and morbidity in living beings
  • Migration and social strife
  • Ill health, hygiene and malnutrition

Mitigation of Droughts:

  • Planting trees and increasing area under trees.
  • Adopting micro-irrigation techniques.
  • Adopting water harvesting measures at both community and individual levels.
  • Wastewater treatment and sustainable use of water resources.
  • Improving national capabilities like training and human resource development for assessing water resources and determining water use.
  • Encouraging NGOs and other organisations like ‘Paani Foundation’.

Floods in India

  • As defined by the IMD, a flood is a condition that occurs in a short time (usually less than six hours) of heavy or excessive rainfall, a dam or levee failure.
  • With the increase in population and development activity, a more serious nature of damage is being seen due to a tendency of occupying the floodplains.
  • Often, because of the varying rainfall distribution, a severe inundation is being experienced in areas which are not traditionally prone to floods.
  • In 1980, as per the assessment done by the Rashtriya Barh Ayog (National Commission on Floods), total area liable to flooding in the Country that is one-eighth of the country’s total geographical area.

Causes of floods in India:

  • Natural causes like heavy rainfall, cyclones etc.
  • Deforestation and climate change.
  • Inadequate capacity of rivers to carry the raised flood discharge.
  • A dam or levee failure.
  • Heavy construction and urbanization encroached on river banks.
  • Obstruction of free flow of rivers.
  • Inadequate drainage arrangement.

Impacts of floods:

  • Loss of lives and livelihoods.
  • Ecological destruction.
  • Socio-economic losses.
  • Destruction of basic infrastructures like communication, transport, sanitation.

Mitigation of floods:

  • Adoption of modern technologies and early warning mechanisms for forecasts to take preparedness measures.
  • Mapping and management of floodplains.
  • Coordination mechanism for states at Central level.
  • Improving national capabilities like training and human resource development.
  • Reducing the vulnerability of physical settlements and structures in which people live.
  • Adopting stricter norms for heavy constructions in floodplain areas.
  • Scientific hydrology coupled with traditional wisdom of water saving methods.
admin
By admin August 10, 2019 15:52