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

Événement

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

Synthetic Aperture Radar (SAR) data can be acquired day and night, even in cloudy conditions, providing a dense time-series suitable for trend analysis and change detection.  Environmental applications for SAR data include:

  •     forest inventory, biomass estimation and condition monitoring
  •     emergency response to floods and landslides
  •     habitat and crop mapping
  •     soil moisture monitoring
  •     offshore infrastructure and vessel monitoring
  •     detection of pollution such as oil spills and illegal waste

The Joint Nature Conservation Committee (JNCC) is organising a series of online training sessions on understanding, accessing and using SAR data. The training will be delivered by Iain Woodhouse, Professor of Applied Earth Observation at the University of Edinburgh and author of Introduction to Microwave Remote Sensing.

... read more

Actualités

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:
Screenshot of the FAO Hand-in-Hand geospatial platform.

The Food and Agriculture Organization of the United Nations (FAO) has launched a geospatial data platform that aims to help build stronger food and agriculture sectors post COVID-19. The Hand-in-Hand system provides access to a wide range of data on food, agriculture, socioeconomics and natural resources.

The 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. A video describing the tool and its use cases is available online.

The data included in the system has been sourced from FAO and other leading public data providers across the UN and NGOs, academia, private sector... read more

Publishing date: 09/09/2020
Tropical cyclone Fani over the eastern coast of India on 2 May 2019. Image: NASA.

According to the latest issue of an annual disaster statistics report, floods were the deadliest type of disasters in 2019, followed by extreme temperature, while storms affected the highest number of people. Published by the Centre for Research on the Epidemiology of Disasters (CRED), “Natural disasters 2019 - Now is the time to not give up” draws on data recorded in the Emergency Events Database (EM-DAT), which saw the addition of 396 disasters that affected a total of 95 million and caused $103 billion in economic losses around the world. 

Accounting for 40 per cent of disaster events, Asia suffered the highest impact with 45 per cent of deaths and 74 per cent of total affected. India, which saw cyclone Fani cause destruction in 2019, was the country most affected... read more

Publishing date: 20/08/2020
Areas flooded and damaged following cyclone Idai, northwest of Beira. Image: European Union/Christian Jepsen.

In recent years, Mozambique has suffered severe floods and droughts that have impacted urban and rural communities throughout the country. In the March and April 2019, tropical cyclones Idai and Kenneth triggered major floods in Mozambique, Malawi, Zimbabwe, and Comoros.  The Port of Beira was hard hit, as cyclone Idai destroyed transmission lines and bridges, leaving the port without access to these lifelines for several days.   In contrast the powerful El Niño event of 2016 triggered major droughts that affected most of the country. Thousands of farmers lost their crops and their cattle and had to rely on humanitarian assistance to cope with the impacts of this event.

Taking into consideration the benefits of the use of satellite imagery to map the geographic extent of floods and to monitor the effects of drought on vegetation; 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... read more

Publishing date: 10/08/2020
Regional Support Offices mentioned:
Sentinel 3. Image: ESA.

A new project of the European Space Agency (ESA) aims to combine data from two different Copernicus Sentinel missions to provide estimates of evapotranspiration at the scale of a single field. The European Space Agency’s Sentinels for Evapotranspiration (Sen-ET) project brings together optical data from the Sentinel-2 mission and thermal data from the Sentinel-3 mission to produce evapotranspiration maps at a resolution of 20m. This is not only relevant for sustainable agriculture, but also for water resource management, and can help understand and respond to climate variability, predict droughts and address heatwaves.

Evapotranspiration describes the process of water being transferred from the Earth’s land and ocean surfaces to the atmosphere through evaporation and transpiration from plants. Monitoring evapotranspiration helps identify crops... read more

Publishing date: 31/07/2020
Central-pivot agricultural fields along the Orange River in South Africa. Image: contains modified Copernicus Sentinel data (2016), processed by ESA.

A grantmaking collective committed to creating and mobilizing labeled datasets that facilitate the development of machine learning applications to address urgent problems has launched a new request for proposals (RFP) for funding. Lacuna Fund, which aims to support as many organizations as possible in using artificial intelligence for social good in low- and middle-income contexts, focuses on agriculture, health and languages. This latest request for proposals will fund labeled agricultural datasets for machine learning in sub-Saharan Africa, whether referenced to Earth observation data or related to other aspects of the crop and animal agricultural system.

Interested organizations headquartered in Africa or having a substantial partnership with organization(s) headquartered in Africa can submit their applications until 3 September 2020. Further details are available... read more

Publishing date: 29/07/2020

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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