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).

Related content on the Knowledge Portal

Actualités

Screenshot of the SMAP tool in action. Image: NASA

Officially launched in 2015 by the National Aeronautics and Space Administration (NASA), the SMAP mission is an orbiting satellite that measures the amount of wetness in the top layer of soil incrementally every 2-3 days. These Soil Moisture Active Passive (SMAP) measurements rely on radiation frequencies that point to different levels of moisture on the surface of  earth’s soil and are useful for scientists because it allows them to construct maps indicating the level of soil moisture globally. Acknowledging the relevance and usability of this data for the field of disaster management, NASA recently integrated the SMAP data into its Disasters Mapping Portal

The Disasters Mapping Portal has been developed by the Geographic Informations Systems (GIS) Team at NASA in an effort to make their satellite data... read more

Publishing date: 25/11/2020
Cover of the IFRC World Disasters Report 2020. Image: Indian Red Cross Society.

A new report by the world’s largest humanitarian aid network highlights global disasters, populations most vulnerable to them and the efforts of local institutions in preventing, preparing for and responding to them. The 2020 edition of the World Disasters Report, “Come Heat or High Water”, was launched virtually from the offices of the International Federation of Red Cross and Red Crescent Societies (IFRC) in Vienna on November 16. This year’s report discusses climate- and weather-related disasters and their humanitarian impact. It argues for the usefulness of smart financing and space-based information in disaster management support.

The report warns that the global effort to address climate change is leaving behind countries most vulnerable to... read more

Publishing date: 19/11/2020
Participants at the virtual expert meeting. Image: UNOOSA.

In order to discuss and promote the use of space technologies in addressing natural hazards such as forest fires and landslides in Latin America, UN-SPIDER conducted a virtual regional expert meeting on the topic of “Space-based Solutions for Disaster Risk Reduction and Emergency Response in Latin America” from 22 to 24 September 2020. The meeting was jointly organized with UN-SPIDER Regional Support Offices from Argentina (National Space Activities Commission, CONAE), Brazil (Federal University of Santa Maria, UFSM), Colombia (Geographic Institute Agustin Condazzi, IGAC), and Mexico (Mexican Space Agency, AEM).

In Latin America, UN-SPIDER and its Regional Support Offices have regularly carried out regional expert meetings, training courses and other joint efforts since 2011. The last Regional Expert Meeting took place in 2017 in Mexico.

The meeting, which consisted of three two-hour-long sessions, brought together a total of over 200 disaster management stakeholders... read more

Publishing date: 28/09/2020
IWMI staff receiving the GeoSpatial World Excellence Award 2020. Image: IWMI.

The International Water Management Institute (IWMI), a UN-SPIDER Regional Support Office, has won an award for its innovative work using remote sensing technology to help nations monitor and mitigate the impacts of drought. The Institute received the GeoSpatial World Excellence Award 2020 in recognition of the positive impact of its South Asia Drought Monitoring System (SADMS). Since IWMI launched SADMS in 2014, the system has guided national, state and district-level authorities in India and Sri Lanka to take timely action to prepare for drought.

The South Asia Drought Monitoring System (SADMS) provides maps of drought conditions that are produced and maintained at IWMI. Numerous drought indices - including the Integrated Drought Severity Index (IDSI), Standardized Precipitation Index, and Soil Moisture Index - have been developed to provide advanced drought monitoring and assessment information. The system has three components:... read more
Publishing date: 27/09/2020
Regional Support Offices mentioned:
Screenshot of the Earth Map platform.

Google and the Food and Agriculture Organization (FAO) of the United Nations have launched a new tool that provides access to multidimensional maps and statistics showing key climate and environmental trends. Earth Map draws on the processing power of Google Earth Engine and aims to help develop insights based on satellite and FAO’s agriculturally-relevant data alike. It follows the joint development by Google and FAO of the Collect Earth platform for forest and land cover assessments, and integrates with the recently launched FAO Hand-in-Hand geospatial platform.

Tapping into the wide range of multi-temporal and quasi real-time satellite data available through Google Earth Engine, Earth Map provides... read more

Publishing date: 18/09/2020
A SpaceX Falcon 9 rocket launches the SAOCOM 1B satellite. Image: Manuel Mazzanti/CONAE

The Argentinean SAOCOM 1B satellite was successfully launched into orbit on 30 August 2020. Developed by the National Argentinean Space Commission (CONAE), this new satellite will join SAOCOM 1A and four Italian COSMO-SkyMed to complete the joint Italian-Argentinean Satellite System for Emergency Management (SIASGE). Like its predecessor, SAOCOM 1B was built in Argentina through a joint effort with private companies and universities. It will operate at an elevation of 620 kilometers above the surface of the Earth. A SpaceX Falcon 9 booster launched the satellite from Space Launch Complex 40 at Cape Canaveral Air Force Station in Florida, United States of America.

The SAOCOM 1B satellite has been fitted with a Synthetic Aperture Radar (SAR) sensor that makes use of microwaves in the electromagnetic L-band, which goes through clouds... read more

Publishing date: 14/09/2020
Regional Support Offices mentioned:

Événement

Participants at the virtual expert meeting. Image: UNOOSA.

En décadas recientes muchas comunidades en América Latina y el Caribe han experimentado desastres ocasionados por inundaciones, sequías, deslizamientos, terremotos, erupciones volcánicas y maremotos o tsunamis que han erosionado los logros asociados a procesos de desarrollo. Además, en este año 2020 la pandemia ocasionada por el virus COVID-19 ha impactado a muchos países del mundo, forzando a los gobiernos, al sector privado, a la sociedad civil y a organismos regionales e internacionales a modificar sus planes de trabajo. De manera paralela, varios países del Este de África, del Sudoeste de Asia y de América Latina están experimentando los impactos de la plaga de langosta.  

Convencidos que las tecnologías espaciales pueden jugar un papel preponderante en apoyar los esfuerzos que llevan a cabo las instituciones en materia de gestión para la reducción de riesgos, la preparación, la respuesta y la recuperación en caso de desastres; la Asamblea General de las Naciones Unidas... read more

Image: UFSM.

The Federal University of Santa Maria of Brazil (UFSM), in its role as a UN-SPIDER Regional Support Office (RSO), and UN-SPIDER joined forces to conduct a virtual seminar on the use of the UN-SPIDER Recommended Practices to process satellite imagery to map the geographic extent of floods, and to elaborate a series of maps that allow government agencies, as well as regional and international organizations, to assess the severity of droughts in particular years in comparison to droughts in other years. The webinar, conducted on 4 August 2020, brought together more than 30 officers of government agencies of Mozambique, as well as researchers, faculty members and students from various universities.

During the event, researchers from UFSM made participants aware of efforts by the space community to develop drought indices extracted from satellite imagery that assess the impacts of drought on vegetation.  They also gave participants a brief introduction to the use of radar imagery... read more

Regional Support Offices mentioned:

The coronavirus pandemic is compounding the impact of drought, which is already affecting more lives than ever with serious impact on health, the economy and the environment.

Droughts cannot be avoided but their impact can be mitigated by adopting a pro-active approach to drought risk management. In this webinar, a special focus will be given to innovative tools and measures, including monitoring and early warning systems, vulnerability assessment and risk mitigation measures, in the context of the current pandemic.

The UNCCD has last year launched an interactive Drought Toolbox that serves as a platform to provide drought stakeholders with easy access to tools to support the implementation of national drought plans to boost the resilience of people and ecosystems against droughts. As no amount of early warning will work without action to protect the most vulnerable, it is important to combine better forecasts with detailed knowledge on how landscapes and societies... read more

Data Source

Publishing institution: Food and Agriculture Organization of the United Nations (FAO)
The online platform features over one million geospatial layers and thousands of statistics series related to food security, crops, soil, land, water, climate, fisheries, livestock, forestry and more. It also includes information on COVID-19's impact on food and agriculture.

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