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Sequía

Lake Chad has shrunk dramatically over the last four decades due to a decrease in rainfall and an increase in the amount of water used for irrigation projects. Its surface area was 25 000 sq km in the early 1960s, compared with 1350 sq km in 2001. Image acquired 19 December 2007 by the MERIS (Medium Resolution Imaging Spectrometer) instrument aboard ESA’s Envisat satellite. Image: ESA, CC BY-SA 3.0 IGO.

Definition

Drought may be considered in general terms a consequence of a reduction over an extended period of time in the amount of precipitation that is received, usually over a season or more in length. It is a temporary aberration, unlike aridity, which is a permanent feature of the climate. Seasonal aridity (i.e., a well-defined dry season) also needs to be distinguished from drought. It should be noted that drought is a normal, recurrent feature of climate, and it occurs in virtually all climatic regimes (UNDDR).

Facts and figures

Droughts are often predictable: periods of unusual dryness are normal in all weather systems. Advance warning is possible (WHO).

By 2025, 1.8 billion people will experience absolute water scarcity, and 2/3 of the world will be living under water stressed conditions (UNCCD).

Drought can be defined according to meteorological, agricultural, hydrological and socio-economic criteria.

  • Meteorological, when precipitation departs from the long-term normal
  • Agricultural, when there is insufficient soil moisture to meet the needs of a particular crop at a particular time. Agricultural drought is typically evident after meteorological drought but before a hydrological drought
  • Hydrological, when deficiencies occur in surface and subsurface water supplies
  • Socio-economic, when human activities are affected by reduced precipitation and related water availability. This form of drought associates human activities with elements of meteorological, agricultural, and hydrological drought (FAO).

Further information

National Drought Mitigation Center, University of Nebraska, Education section
NASA Earth Observatory, Drought Facts
WMO Handbook of Drought Indicators and Indices

UN-SPIDER Regional Support Offices with hazard-specific expertise

Title: Centro Asiático para la Reducción de Desastres (ADRC)
Title: Centro Internacional para el Aprovechamiento Integrado de las Montañas (ICIMOD)
Title: Instituto Internacional de Gestión del Agua (IWMI)
Title: Oficina de Apoyo Regional de los Estados Unidos de América
Title: Oficina Regional de Apoyo Argentina
Title: Oficina Regional de Apoyo Brasil
Title: Oficina Regional de Apoyo de Alemania
Title: Oficina Regional de Apoyo de Grecia
Title: Oficina Regional de Apoyo de Indonesia
Title: Oficina Regional de Apoyo de Nigeria
Title: Oficina Regional de Apoyo de Pakistán

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UN-SPIDER Regional Support Offices with hazard-specific expertise

Title: Centro Asiático para la Reducción de Desastres (ADRC)
Title: Centro Internacional para el Aprovechamiento Integrado de las Montañas (ICIMOD)
Title: Instituto Internacional de Gestión del Agua (IWMI)
Title: Oficina de Apoyo Regional de los Estados Unidos de América
Title: Oficina Regional de Apoyo Argentina
Title: Oficina Regional de Apoyo Brasil
Title: Oficina Regional de Apoyo de Alemania
Title: Oficina Regional de Apoyo de Grecia
Title: Oficina Regional de Apoyo de Indonesia
Title: Oficina Regional de Apoyo de Nigeria
Title: Oficina Regional de Apoyo de Pakistán

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