Drought

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 Droight 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: Argentina Regional Support Office

Title: Asian Disaster Reduction Center (ADRC)

Title: Brazil Regional Support Office

Title: Germany Regional Support Office

Title: Greece Regional Support Office

Title: Indonesia Regional Support Office

Title: International Centre for Integrated Mountain Development (ICIMOD)

Title: International Water Management Institute (IWMI)

Title: Nigeria Regional Support Office

Title: Pakistan Regional Support Office

Title: United States of America Regional Support Office

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